Progress on Asia-Pacific Space Geodynamics (APSG) Project Cheng Huang

Shanghai Astronomical Observatory, Shanghai, hc@shao.ac.cn

Abstract The Asia-Pacific Space Geodynamics (APSG) Project was initiated, in accordance with IAG Resolution #4 of 1995, in Shanghai, China during May13-17, 1996. The main function of the APSG Project is to unite forces of the Asia-Pacific area to perform cooperative research on lithospheric plate motion, crustal deformation and sea-level change in this area, and to enrich our understandings of the regional geoscientific and environmental issues. The work includes the study of serious nature hazards in this area, providing basic information for predictions and mitigations of earthquake, volcanic eruption and sea immersion. This presentation will introduce the APSG significance, research contents and its organization structure. Especially, the recent progress on APSG project will be presented.

Earth’s Climate History from Glaciers and Ice Cores Lonnie G. Thompson

School of Earth Sciences and Byrd Polar Research Center, The Ohio State University, Columbus, Thompson.3@osu.edu

Abstract Glaciers serve both as recorders and early indicators of climate change. Over the past 35 years our research team has recovered climatic and environmental histories from ice cores drilled in both Polar Regions and from low to mid-latitude, high-elevation ice fields. Those ice core –derived proxy records extending back 25,000 years have made it possible to compare glacial stage conditions in the Tropics with those in the Polar Regions. High-resolution records of δ18O (in part a temperature proxy) demonstrate that the current warming at high elevations in the mid- to lower latitudes is unprecedented for the last two millennia, although at many sites the early Holocene was warmer than today. Remarkable similarities over the last 1000 years between high resolution ice core records from high elevations in the Himalayas and in the tropical Andes of South America argue for large-scale ENSO teleconnections across the Pacific Ocean basin. Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds to thousands of years, suggesting that current climatological conditions in those regions today are different from those under which these ice fields originated and have been sustained. The current warming is therefore unusual when viewed from both the millennial-scale perspective provided by multiple lines of proxy evidence and the 160-year record of direct temperature measurements. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides strong evidence that a large-scale, pervasive and, in some cases, rapid change in Earth’s climate system is underway. Observations of glacier shrinkage during the 20th and 21st century girdle the globe from the South American Andes, the Himalayas, Kilimanjaro (Tanzania, Africa) and glaciers near Puncak Jaya, Indonesia (New Guinea). The history and fate of these glaciers as well as new geo-hazards that their recent retreat has created provide a global perspective for contemporary climate changes.

Quantifying Coastal Vulnerability Due to Sea-level Rise Hazards: Physical Basis C. K. Shum1 & Belmont Forum Project BanD-AID Team Members

1Division of Geodetic Science, School of Earth Sciences, The Ohio State University, ckshum@osu.edu

Abstract Approximately half of the world’s population or 3.2 billion people lives within 200 km of coastlines and many of them in the world’s deltaic plains. Sea-level rise, widely recognized as one of consequences resulting from anthropogenic climate change, has induced substantial coastal vulnerability globally and in particular, in the deltaic regions, such as coastal Bangladesh, and the Yangtze Delta. Bangladesh, a low-lying, one of the most densely populated countries in the world located at the Bay of Bengal, is prone to transboundary monsoonal flooding, potentially aggravated by more frequent and intensified cyclones resulting from anthropogenic climate change. Yangtze Delta is one of the largest and most densely populated deltas, and location of one of the largest mega cities in the world, Shanghai. Sea-level rise, along with tectonic, sediment load and groundwater extraction induced land uplift/subsidence, have significantly exacerbate these risks and Bangladesh’s coastal vulnerability. While Yangtze Delta’s coastal vulnerability is currently being exacerbated due to the compounding effects of population growth, severe land subsidence due to ground water extraction and sediment loading, in addition to plausible accelerated rate of sea-level rise. Here we describe the physical science component of the integrated approach based on both physical and social sciences to address the adaption and potential mitigation of coastal Bangladesh vulnerability for the Belmont Forum project, entitled Bangladesh Delta: Assessment of the Causes of Sea-level Rise Hazards and Integrated Development of Predictive Modeling Towards Mitigation and Adaptation (BanD-AID). The physical science component of the project is to quantify the estimates of spatial varying sea-level trend as well as the vertical motion of the coastal regions using geodetic data (tide gauges, 1950–current; satellite altimetry, 1992–present, GRACE, 2003–present) and

reconstructed sea-level trend estimates (1950–current), and GPS and InSAR observed land subsidence, towards the possible accurate projection of relative sea-level change at the end of the 21st century for the Bangladesh Delta. This paper also provides an example physical basis for the Yangtze Delta coastal vulnerability, which is a completely different social economic coastal region than the Bangladesh Delta.  

Quantifying Coastal Vulnerability Due to Sea-level Rise Hazards: Social Sciences and Integrated Approach

Craig J. Jenkins1 & Belmont Forum Project BanD-AID Team Members 1Department of Sociology, Political Science & Environmental Science, & the Mershon Center for International Security

Studies, The Ohio State University, Jenkins.12@osu.edu

Abstract Approximately half of the world’s population or 3.2 billion people lives within 200 km of coastlines and many of them in the world’s deltaic plains. Sea-level rise, widely recognized as one of consequences resulting from anthropogenic climate change, has induced substantial coastal vulnerability globally and in particular, in the deltaic regions, including coastal Bangladesh and the Yangtze Delta. Here we describe the integrated approach based on both physical and social sciences to address the adaption and potential mitigation of coastal Bangladesh vulnerability for the Belmont Forum project, entitled Bangladesh Delta: Assessment of the Causes of Sea-level Rise Hazards and Integrated Development of Predictive Modeling Towards Mitigation and Adaptation (BanD-AID). A key part of this project addresses the social adaptations of coastal Bangladesh villages to changing sea-level and climate challenges associated with flooding, soil loss, salinization of fresh water and emergency preparedness by constructing an index of climate resilience. Drawing on census data on agricultural production and population and climate records on rainfall extremes and coastal flooding, we will construct a climate resilience index identifying the ability of coastal communities to withstand major climate changes. This will then be used to design a survey of village mayors and residents to develop an understanding of local capacities for adaptability in terms of how villages are organized and act collectively to address pressing climate challenges. The third step in this project will then use scenario construction methods to develop alternative ways in which NGOs (Non-Governmental Organizations) and government agencies can work with local communities to improve their adaptive capacity and prepare for future challenges in coastal erosion, salinization and flooding risk in the next three decades.

Accelerating Rates of Ice Loss in Greenland: Comparing Results from GRACE and GPS Michael Bevis1, Abbas Khan2, Abel Brown1, Ingo Sasgen3, Chris Harig4, Frederik Simons4, Finn Bo Madsen2, Dana

Caccamise1, Eric Kendrick1, Per Knudsen2, Thomas Nylen5, Robin Abbot6 1School of Earth Sciences, Ohio State University, Columbus, Ohio, USA, bevis.6@osu.edu

2DTU Space, Danish Technical University, Copenhagen, Denmark 3GFZ, Potsdam, Germany

4Geosciences, Princeton, USA 5UNACO Inc., Boulder, CO, USA

6Polar Field Services, Boulder, CO, USA

Abstract The Greenland GPS Network (GNET) is recording the motion of the bedrock surrounding the world's second largest ice sheet. One of our main goals is to place geodetic constraints on annual cycles and progressive trends in ice mass. One difficulty for this agenda is separating the constant velocity component of elastic rebound from postglacial rebound (PGR). Another issue is idenitifying and realizing a 'neutral' reference frame in which zero velocity corresponds to zero rebound. Both of these difficulties are pre-empted (or side stepped) if we focus on accelerations in crustal displacement. We can now resolve accelerations at more than half of the GPS stations in Greenland. It is instructive to compare these accelerations with mass accelerations inferred from GRACE. Such comparisons emphasize the complementary nature of the GPS and GRACE approaches ice mass sensing.

Geodetic Estimates of the Regional Mass Evolution of the Polar Ice Sheets

Ingo Sasgen1,2 1German Research Centre for Geoscience, Potsdam, Germany

2The Pennsylvania State University, University Park, PA, United States, sasgen@gfz-potsdam.de

Abstract Space-geodetic observing systems have enabled us to continuously and comprehensively survey the Polar Ice Sheets, helping us to better understand their current evolution in changing climate. Of particular interest is the mass balance of the

ice sheets, characterizing their dynamical state, and governing the related fingerprint of sea-level change. Three main satellite-based techniques are available for observing ice sheet mass balance; 1) measuring variations in the Earth's gravitational potential with the Gravity Recovery And Climate Experiment (GRACE), 2) contrasting the net surface mass balance (SMB) from regional climate modeling with ice discharge (D) over the ground line measured by Interferometric Synthetic Aperture Radar, i.e. the mass budget method, and 3) determining surface elevation changes, e.g. by the Geoscience Laser Altimeter System onboard ICESat. Each method has its strengths and weaknesses; e.g. (laser) altimetry measurements are accurate, but yield volume changes that need to be converted to mass changes with a snow/ice density model; mass balance from SMB minus D gives the best insight into the physical processes, but it relies on subtracting two large and sometimes uncertain numbers. In this respect, GRACE is advantageous, because it records the net ice-mass changes directly - but, particularly for Antarctica, GRACE ice-mass balances are “contaminated” by the gravitational signal from the delayed adjustment of the Earth’s interior to ice loading during the last glacial cycle. Despite these uncertainties, which are regionally very different, we present a promising comparison of basin-scale ice-mass balances for Greenland and Antarctica from GRACE, SMB minus D, and ICESat. This agreement allows us to draw conclusions about the relative importance of precipitation, melt/run-off and discharge in driving the mass balance within the the last decade, and tighten constraints on the related change in sea-level caused by the Polar Ice Sheets.

Global Ice Mass Balance and its Contribution to the Early 21st Century Sea Level Rise Jianbin Duan1, C.K. Shum1, Junyi Guo1, Zhenwei Huang2, Chungyen Kuo3

1School of Earth Sciences, Ohio State University, Columbus, OH, USA, duan.29@osu.edu 2National Administration of Surveying and Mapping, Beijing, China

3Department of Geomatics, National Cheng Kung University, Taiwan

Abstract Sea level change is an important consequence of anthropogenic climate change, both for societies and for the environment. For the past several decades, analysis of tide gauge measurements show an average rise in sea level of 1.7±0.3 mm/yr from 1950 to 2009, while the analysis of satellite altimetry data indicates a rise of 3.3±0.3 mm/yr from 1993 to 2009. Mass imbalance of the polar ice sheets and major mountain glacier systems is one of the main contributors to present-day global mean sea level rise. The Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry mission launched in March 2002 provides a means of unprecedented accuracy and temporal and spatial resolutions to quantify global ice mass changes. In this study, we estimate the global ice mass balance and the associated uncertainty for the world’s ice sheets, major mountain glaciers and ice caps by using GRACE data in the form of monthly gravity field models. Our result shows that the ice mass change rate over Greenland, from Jan 2003 to Dec 2012, is –267±10 Gt/yr, which is equivalent to sea level rise of 0.74±0.03 mm/yr. Evident accelerated ice mass loss in Greenland is found occurring during the time period approximately from 2010–2012. The mass loss rates are about twice for the years before 2010. For Antarctica, we report an estimate of ice sheet mass changes of –118±30 Gt/yr (+0.33±0.08 mm/yr sea level rise). The contributions of mass loss from global mountain glacier and ice caps from 5 major systems including Alaska, Iceland, Canadian Arctic, High Mountain Asia and Patagonia is considerable, at –171�9 Gt/yr, or a contribution to the contemporary sea level rise of 0.48±0.02mm/yr, assuming that the melt water immediately reaches the ocean.

Elevation Changes of Mountain Glaciers and Ice Caps Using Satellite Radar Altimetry Through Collinear Analysis

Hyongki Lee1,2, Ning Cao1,2, C.K. Shum3, Kuo-Hsin Tseng3, Yuchan Yi3, Alexander Braun4 1Department of Civil and Environmental Engineering, University of Houston, Houston, TX, USA, hlee@uh.edu

2National Center for Airborne Laser Mapping, University of Houston, Houston, TX, USA 3Division of Geodetic Science, School of Earth Sciences, Ohio State University, Columbus, OH, USA

4Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario, Canada

Abstract

Satellite radar altimetry has been extensively used to estimate ice-sheet elevation change rates over Antarctica and Greenland from repeated measurements of surface elevation changes through either crossover or collinear (repeat-track) analysis. However, there has been no attempt to use satellite radar altimetry over mountain glaciers because the instrument often loses lock or does not provide usable measurements over the rough terrains and steep slopes due to its large footprint size. The radar altimetry has been only recently used to estimate ice cap elevation changes using only a few number of cross over locations. In this study, we use a suite of historic and contemporary satellite radar altimeters including TOPEX/Poseidon (T/P), Envisat, and Jason-2 to estimate elevation changes of mountain glaciers including the Bering Glacier in Alaska, and ice caps in the Canadian Archipelago, through the collinear analysis. Over the Bering Glacier, we were able to observe the 1993~ 1995 and 2008~ 2011 surge events from the T/P and Envisat time series, respectively. We

also observed accelerated elevation decreases in 2002~ 2007, after slightly negative or near nil elevation changes in 1996~ 2001, which were related to temperature and snow depth variations. The ice caps in Canadian Archipelago have undergone about -0.5 ~ -1.0 m year-1 of elevation decreases in 2002~ 2010 without significant acceleration. Our method will provide new insights into the behavior of the mountain glaciers and ice caps responding to global warming.

Inter-annual Variations of Greenland Ice Sheet Revealed by ENVISAT Radar Altimetry and GRACE Xiaoli Su, Junyi Guo, Yuchan Yi, C.K. Shum, Ian Howat, Jianbin Duan

Division of Geodetic Science, School of Earth Sciences, Ohio State University, Columbus, OH, USA, su.282@osu.edu

Abstract Mass changes of Greenland ice sheet (GrIS) is of considerable concern since its possible contribution to sea level rise in the context of global warming. Using measurements from two techniques, Envisat radar altimetry and GRACE, the inter-annual components of elevation change and mass variation which, is indicated by equivalent water height are compared. It is found that the inter-annual components from both technologies show high correlation with each other, which suggests both techniques detect the same geophysical process. Furthermore, in basin scale, the surface density on inter-annual scale for each basin is estimated by linear regression, which will improve the accuracy of mass balance estimate from altimetry.

Using Multiple Spaceborne Sensors to Quantify Tianshan Glacier Mass Balance Change Kuo-Hsin Tseng1, C.K. Shum1, Alexander Braun2, J. Graham Cogley3, Jianbin Duan1, Hyongki Lee4, Kefeng Zhu1

1Division of Geodetic Science, School of Earth Sciences, Ohio State University, USA, tseng.95@osu.edu 2Department of Geological Sciences and Geological Engineering, Queens’s University, Canada, braun@queensu.ca

3Department of Geography, Trent University, Canada, gcogley@trentu.ca 4Dept. of Civil & Environmental Engineering, University of Houston, USA

Abstract

The Tianshan mountain ranges on the borders of Kyrgyzstan, Kazakhstan, and China have experienced substantial glacier wastage during the last few decades. Multiple spaceborne sensors such as Gravity Recovery And Climate Experiment (GRACE) gravimetry since 2003, and ICESat laser altimetry during its intermittent campaigns in 2003–2009, have observed notable mountain glacier mass balance changes or surface elevation changes across the central Asia. However, an extended time series of observations as well as an expanded surface coverage are imperative for the exact quantification of glacier mass balance. Here, we exploit Landsat Thematic Mapper (TM) and Enhanced TM Plus (ETM+) onboard Landsat 4, 5, and 7 towards quantifying changes of glacier extent and surface elevation since 1989. We introduce a Thematic Imagery-Altimetry System (TIAS) to estimate glacier surface elevation change by integrating Landsat images and a digital elevation model (DEM), namely the SRTM X-band DEM at 30 m resolution. We estimate the thinning rate of the glaciers along their outlines via the TIAS, and combine with extent variation to estimate a mass balance change in the last 20 years. Our result is comparable with previous studies using independent observations, implying that this alternative technique is viable.

Progress of Precise Gravimetry Technology and Application Prospect Houtse Hsu

Institute of Geodesy & Geophysics, CAS, hsuh@whigg.ac.cn

Abstract Following the success of satellite gravity mission, cold-atom interferometry gravity system, superconducting gravity technique, gravity gradiometers, airborne gravimetry, the precise high gravimetric techniques have achieved rapid and huge progress in recent years. Respect to this subject, we give a review on the application outlook of these new developments in the field of monitoring of environment changes, unification of height system, submarine navigation, mine exploration and earth science researches.

Future Gravity Missions Using a Superconducting Gravity Gradiometer Ho Jung Paik

Department of Physics, University of Maryland, College Park, MD 20742, USA, hpaik@umd.edu

Abstract

The superconducting gravity gradiometer (SGG) is a viable technology to reduce the cost, size, and complexity of GRACE-II. The SGG requires only a single spacecraft, measures all the tensor components of gravity, and is more sensitive to short-wavelength gravity field (smaller scale mass change) than the satellite-to-satellite tracking (SST) method used by

GRACE. While the GOCE data improved the spatial resolution over GRACE, they are not sensitive to time-variable gravity fields that are crucial for studying climate change and natural hazards. The SGG integrated with a long-duration cryocooler could measure in situ gravity gradients from spacecraft for time-variable gravity observations.

A new and innovative design, based on levitated superconducting test masses, gives the SGG a potential sensitivity better than 3 × 10−5 E Hz−1/2 in the 0.001-0.05 Hz frequency band. The 4-K space cryocoolers under development and near flight test can reduce the liquid helium payload to meet the stringent mass requirement of a low Earth orbiting satellite (around 400 kg like that of GRACE) and enable multi-year gravity mapping missions. With these two technologies combined, a future gravity gradiometer mission would improve the gravity resolution by two to three orders of magnitude over GOCE over a substantially wider frequency band. The advantage of the SGG over SST becomes more pronounced for planetary missions where precise tracking between two co-orbiting spacecraft is more challenging.

In this paper, I will introduce the principle of gravity gradiometry, and discuss the design and performance of the SGG. I will then discuss the concept of future SGG missions for the Earth and planets. I will also present the anticipated gravity recovery for hydrology signals from the SGG mission compared with GRACE.

Global Temporal Gravity Field Recovery Using GRACE Data M. Zhong1, J.J. Ran1, 2,H.Z. Xu1, W. Feng1,2, Y.Z. Shen3,4, X.F. Zhang5, W.Y. Yi6

1State Key Lab. of Geodesy & Earth’s Geodynamics Chinese Academy of Sciences, Wuhan, China, zmzm@whigg.ac.cn 2University of Chinese Academy of Sciences, Beijing, 100049, China

3Collegeof Surveyingand Geo-informatics, Tongji University, Shanghai, 200092, China 4Center for Spatial Information Science and Sustainable Development, Tongji University, Shanghai, PR, China

5Faculty of Civil and Transportation Engineering, Guangzhou, 510006, China 6Institute of Astronomical and Physical Geodesy, Technical University Munich, 80333 Munich, Germany

Abstract

The first version of IGG-CAS series temporal gravity field model is recovered in this study using GRACE data and compared with the RL04 and RL05 version of temporal gravity models from three research institutes, which are well known as satellite gravity research, for instance, CSR (Center for Space Research), GFZ(Geo Forschungs Zentrum) and JPL(Jet Propulsion Laboratory). The accuracy of IGG-CAS model is better than the RL04, but lower than RL05, according to the geoid height per degree comparison. After applying the same de-stripe and Gauss filter to the four series temporal gravity models (IGG-CAS, GFZ, CSR and JPL) from Jan 2004 to Dec 2010, the time signal of continental water recovered from those four models are very similar. Especially, the correlation coefficients of the signal of Yangtze River valley among the four models are higher than 0.8. the square root of the signals of Sahara desert from the IGG-CAS, CSR-RL05, GFZ-RL05 and JPL-RL05 are 1.5cm、1.1cm、1.1cm and 1.2cm in terms of equivalent water height, respectively. To sum up, it shows IGG-CAS reaches almost the same accuracy level when compared with the kind of products which are released by other famous institutes in the world. Keywords: GRACE, temporal gravity field, IGG-CAS, equivalent water height, integrated equation approach

GOCE and Isostatic Models for the Lithosphere of the Bolivian Andes Christopher Jekeli

Division of Geodetic Science, School of Earth Sciences, Ohio State University, jekili.1@osu.edu

Abstract Bouguer and isostatic gravity anomalies are formulated using global spherical harmonic models of the gravitational field and the visible topography. From the approximate equivalency of topographic masses and surface density layers using the Helmert condensation method isotropic transfer relations are derived between the spectra of topographic loads and elastic spherical shell deflections, where the Airy isostatic compensation is the special case of no lithospheric flexural rigidity. Parameters for these isostatic models are determined for the Bolivian Andes using the Gravity field and steady-state Ocean Circulation Explorer (GOCE) gravitational field. Results agree reasonably with values derived from historical seismic and gravity data for the depths of compensation of the crustal roots under the Andes and for the flexural rigidity of the elastic lithosphere of the Sub-Andes to the east. The relatively high and uniform resolution of the satellite gravitational model produces more detailed maps of the isostatic anomaly that clearly delineate the flexure of the Brazilian shield that is thrust under the Sub-Andes. Additional structural detail not seen in previous seismic and gravity investigations emerges from these maps, showing, for example, the bend of the Andes in Bolivia that comes to a sharp breakpoint at the margins between the fold-and-thrust belt of the Sub-Andes and the lowlands further to the east, consistent with earlier theories for a divergent crustal deformation associated with the confluence of the subducted Nazca plate and the Brazilian craton.

Geocenter Motion Derived by SLR/GRACE and Satellite Altimetry Chung-Yen Kuo1, Jun-Yi Guo2, C.K. Shum2, Yu-Ling Tai1, Zhenwei Huang2, Jianbin Duan2

1Department of Geomatics, National Cheng Kung University, Tainan, Taiwan. kuo70@mail.ncku.edu.tw 2Division of Geodetic Science, School of Earth Sciences, Ohio State University, Ohio, USA.

Abstract

Geocenter variations, the motion of the Center of Mass (CM) of the Earth system relative to its Center of Figure (CF), have been traditionally estimated using SLR, GPS, or DORIS satellite tracking data, or by combining GPS, GRACE gravimetry and ocean circulation model predicted ocean bottom pressure (OBP) data. In the study, a theoretical basis for the geocenter motion is developed, with an intent to estimate its seasonal, interannual and secular variations, and accounting for possible drift in the International Terrestrial Reference Frame (ITRF), degree one glacial isostatic adjustment effects, the associated elastic loading and Love numbers, present-day ocean mass variations. We then provide an estimate of geocenter motions, by combining GRACE/SLR, AVISO altimetry and Argo hydrographic measurements covering 2002–2011 or 1993-2011. Here, geodetic observations in favor of ocean model predicted ocean bottom pressure variations, thus better retaining the low-frequency component of the recovered geocenter variations. Compared to GRACE solutions, SLR gravity field solutions covering almost 20 years can be used to compute a longer time-span geocenter motion. In addition, the effect of the degree-one terms from the GIA process and its separation from present-day mass change is considered here.

The Response of Prairie Lakes to Extreme Variability in Climate: Integrated Observational and Model-based Analyses

Franklin W. Schwartz and Ganming Liu School of Earth Sciences, The Ohio State University, Columbus, Ohio, schwartz.11@osu.edu

Abstract

The prairie pothole region (PPR), covering 750,000 km2, is the most productive wetland habitat for waterfowl in North America. Satellite observations for the first time make it possible to describe spatially the exact numbers of ponds, lakes, and wetlands in the PPR. Landsat data has shown that water areas and numbers of potholes follow well-defined power laws. Their slopes and intercepts change intra-annually and interannually as a function of climate. Yet, there are limitations with these data in terms of backwards availability of records in time, numbers of cloud-free days, and resolution. A new type of hydrologic model applicable to a diverse assemblage of surface-water bodies provides quantitative understanding of water-body numbers and their stages. The super-resolved calibration of this model is novel because it integrates power-laws developed from satellite observations, and long-term measurements of wetlands in the Cottonwood Lake Study Area in a Genetic Algorithm framework. Results for the 20th Century show the tremendous variability in pothole systems through long terms droughts (e.g., Dust Bowl Drought of the 1930s) and a recent deluge (1993-2001). The time required for surface waters to adjust to drier or wetter conditions is proportional to the size of the water body. Thus drying in spring through summer months in a given year mostly affects the puddles and smaller potholes in the complex. The larger potholes and lakes respond to droughts and deluge that span a number of years. Our most recent studies extend this approach to show how inherent climate-driven variability can influence ecological interconnections.

On the Development of An Integrated Modeling System for the Estimates of River Discharge from Space Ganming Liu and Franklin W. Schwartz

School of Earth Sciences, The Ohio State University, Columbus, Ohio, liu.699@osu.edu

Abstract Knowledge of the spatial and temporal dynamics of surface water storage, and discharge of rivers and streams, is critically important to understand and quantify the global water balance. By 2025, it is estimated that five billion people worldwide will be living in water-stressed countries. Moreover, it is likely that anthropogenic climate change will aggravate this problem and potentially create grave U.S. national security concerns in particular regions of the world. Anticipating these problems and providing a response will require knowledge of dynamical behavior of surface water storage and the discharge of rivers. This study aims to develop a novel space-based and integrated hydrologic and hydraulic modeling system, called SXG, to estimate river channel bathymetry and discharge over any inaccessible regions in the world. The SXG system relies on SWAT and XSECT models to estimate river discharge and water depth, respectively. It takes the satellite observational data (e.g., river stages or water surface heights from Envisat altimetry, water surface areas from Landsat) as optimization or calibration targets, and compares them with their counterparts from model simulations. The SXG system has been successfully applied to the Red River of the North and has proven to be a powerful approach for estimating basin-scale river discharge and water depths based on satellite observations alone. We envision that outcomes from the SXG applications can directly benefit the need to estimate discharge of rivers in the world with a view to understanding and quantifying the global water cycle.

Prediction of Water Levels of the Helmand River Using Satellite Data

Motomu Ibaraki and Donald Barchorowski School of Earth Sciences, The Ohio State University, Columbus, Ohio, ibaraki.1@osu.edu

Abstract

Satellite observation data has been used for many analyses in order to obtain great insight into how the Earth is changing and responding to both natural and anthropogenic influences. Most of these studies have focused on understanding past and current situations. In this study, on the other hand, we use satellite observation data to make predictions using Case Based Reasoning (CBR). CBR is a data mining technique used in various artificial intelligence applications, which uses the knowledge base or history of a system to make predictions about expected outcomes. It is reasonable to assume that situations with similar circumstances will yield similar results. In order to make a prediction, CBR explores an existing knowledge base to find situations (i.e., cases) that are similar to the case for which we are going to predict an outcome. CBR finds similar cases by comparing a cases' attributes which describes the characteristics of the cases. Each attribute is assigned a weighting factor that represents its importance when comparing cases. Weight for an attribute is determined based on its impact on the accuracy of prediction during the model calibration process. Using the data for soil moisture from MODIS and precipitation from TRMM as the attributes, we apply CBR in order to predict water levels for the Helmand river in Afghanistan. The Helmand is the largest river watershed in Afghanistan covering the southern half of the territory. The primary supply of flow to the Helmand is the annual snow pack from the Sia Koh and Parwan mountains, which leads to large seasonal fluctuations in water levels. In order to apply CBR to the Helmand river watershed, we make each case composed of twenty attributes, which are the soil moisture and precipitation for each of ten contributing watersheds for the river. The past cases are ranked based on their similarity to the current case for which we are predicting the river's water level. The water levels of the similar cases are then revised to make a water level prediction for the current case. Preliminary results show that the satellite data can be used in conjunction with CBR to make predictions that could possibly be used for flood prediction and mitigation. CBR has promise as a quick alternative to more involved physical-based modeling.

Wetland Monitoring Using SAR/InSAR Technology Jin Woo Kim1, C. K. Shum1, Yuanyuan Jia1, Zhong Lu2, John W. Jones3

1Division of Geodetic Science, School of Earth Sciences, The Ohio State University, kim.2364@osu.edu 2U.S. Geological Survey, Vancouver, WA, USA

3U.S. Geological Survey, Reston, VA, USA

Abstract Development of coastal wetlands had negative impacts on the natural hydrological processes, resulting in the disappearance of wetlands that buffer severe flooding, cyclones/hurricanes, and as a natural habitat for diverse wildlife in the wetlands. The intensity and phase components of Synthetic Aperture Radar (SAR) data provide valuable information on the characteristics of surface change and displacement. In this study, we demonstrate the capabilities of InSAR phase measurements and SAR backscatter coefficients to quantify wetland water level changes in the Atchafalaya Basin of the Louisiana and the Florida Everglades, with high spatial sampling. The InSAR phase has the potential to estimate the relative water level change as well as absolute water level change through an integration with other available data such as in situ gage data or satellite altimetry. The SAR backscatter coefficient can be used not only for wetland classification, but also for inferring hydrological change under a certain condition.

Satellite Altimetry and Hydrology Modeling of Poorly-gauged Tropical Watershed

Y Budi Sulistioadi1,3, Michael T Durand1, Kuo-Hsin Tseng1, C.K. Shum1, Hidayat2, Sumaryono MS3, Sigit Hardwinarto3 1 Division of Geodetic Science, School of Earth Science, The Ohio State University, Columbus Ohio, sulistioadi.1@osu.edu

2 Hydrology and Quantitative Water Management Department, Wageningen University, The Netherlands 3 Faculty of Forestry, Mulawarman University, Kampus Gunung Kelua Jl. KH Dewantara, Samarinda, 75123 Indonesia

Abstract

Fresh water resources are critically valuable for daily human consumption. Therefore, a continuous monitoring effort over their quantity and quality is instrumental. One important model for water quantity monitoring is the rainfall-runoff model, which represents the response of a watershed to the variability of precipitation, thus estimating the discharge of a channel. In the context of poorly-gauged watershed, where the daily precipitation and discharge data from ground stations are not available, the use of remotely sensed data in the form of Tropical Rainfall Measuring Mission (TRMM) rainfall estimates and water level derived from satellite altimetry is promising. However, given the level of uncertainty of the TRMM rainfall estimates, it is necessary to calibrate the dataset with available in-situ precipitation measurement before incorporating them

into the hydrology model. Another challenge for a poorly-gauged watershed is the scarcity of channel geometry measurement, which is required to develop a reliable hydrologic routing. To address this scientific challenge, this study is conducted with the main objective to develop a rainfall-runoff hydrological model to represent the response of mesoscale watershed to the variability of precipitation. In addition to the main objective, satellite altimetry derived water level changes are used as the source of validation of the hydrological model through data assimilation. Upper Mahakam watershed in Indonesian Borneo is chosen as the study site, considering its characteristics as a poorly gauged watershed, where only limited discharge measurements are available for validation and calibration. This study modeled the response of the poorly-gauged watershed in the Southeast Asia’s humid tropic through the application of Hydrologic Engineering Center – Hydrologic Modeling System (HEC-HMS) with Soil Conservation Service (SCS) Curve Number as the method for runoff volume module, Clark unit hydrograph as the method for direct runoff generation, Muskingum-Cunge as the method for hydrologic routing module and exponential recession as the method for baseflow computation. Among the input data used to develop the HEC-HMS Model are Tropical Rainfall Measuring Mission (TRMM) daily rainfall estimate, soil type and land cover maps, and a number of estimations including Manning’s n, storage coefficient (R) for the Clark Unit Hydrograph method and channel bottom width were involved in the development of the parameters for each sub-basins. This study demonstrates that HEC-HMS with the choice of modules listed above was capable to continuously simulate the discharge in the period of one year. The resulted discharge also shows correlated timing as it is compared with the occurrence of floods during the period of 2002-2010. The performance evaluation of HEC-HMS discharge estimation confirms a good match between the estimated discharges with the observed ones. This research also proposes a novel approach to spatially process the TRMM daily precipitation estimation through Thiessen polygon and area average hybrid method, which model the spatial distribution of TRMM data to match the spatial location of field meteorological stations. Apart from the results from the hydrological model, this study also demonstrates the use of Envisat RA-2 satellite altimetry data as the source of discharge validation. The water level change as derived from satellite altimetry measurement was converted into discharge through a rating curve, which then incorporated into the developed hydrological model through data assimilation approach. While the experiment ended up with various results, it is interesting to further investigate various data assimilation setup toward the best estimate of discharge in the study area.

Monthly Gravity Field Model Solutions Using GRACE Level 1B Data Shen Yunzhong1，2, Chen Qiujie1，2, Hsu Houze3, Zhang Xingfu4

1College of Surveying and Geo-informatics, Tongji University, Shanghai, China, yzshen@tongji.edu.cn 2Center for Spatial Information Science & Sustainable Development, Tongji University, Shanghai, China

3State Key Laboratory of Geodesy and Earth’s Geodynamics Chinese Academy of Sciences, Wuhan, China 4Departments of Surveying and Mapping, Guangdong University of Technology, Guangzhou, China

Abstract We have modified the short arc approach by linearizing the observation equation with respect to the GNSS determined orbit and modeling the orbit error and the range rate observation error and the parameters including the harmonic coefficients of gravity field model and the bias parameters of acceleration measurements in a combined observational equation. In our modified approach, the initial state parameters of satellite orbit and initial gravity field model are no longer needed. By using the real GRACE orbits, the range rate and acceleration measurements officially released by JPL (Jet Propulsion Laboratory), we have computed the monthly gravity field model series from Jan. 2004 to Aug. 2011 up to degree and order 60 with our modified short arc approach. In our solutions, the short arc length is 2 hours, and the initial state vector needn’t to be solved. By comparing the degree geoid errors of our model with the RL05 models released respectively by CSR (Centre for Space Research), JPL and GFZ (GeoForschungsZentrum), we show that our solution is as accurate as the released RL05 models. Then we apply our solutions to analyze the ice mass changes in Antarctic, the results are also closed to that derived from the RL05 models. Keywords: Satellite gravimetry; Monthly gravity field model; GRACE mission; Short arc approach

GRACE Temporal Gravity Field Recovery Using An Improved Energy Balance Approach: A Case Study of AOD1B Data

Kun Shang1, Junyi Guo1, Jia Luo1,3, C.K. Shum1, Jianbin Duan1, Ehsan Forootan2, Jürgen Kusche2, Chunli Dai1

1Division of Geodetic Science, School of Earth Sciences, The Ohio State University, Columbus, Ohio, shang.34@osu.edu 2Institut für Geodäsie und Geoinformation, Universität Bonn

2School of Geodesy and Geomatics, Wuhan University, Wuhan, China

Abstract The Earth’s mass transport signals estimated from monthly temporal gravity field models using data from the Gravity Recovery and Climate Experiment (GRACE) twin-satellite mission have removed the effects of tides and the non-tidal mass

variations in the atmosphere and ocean, as well as their high-frequency aliasing effects leaking into the signals due to the spatio-temporal sampling of the GRACE orbits. The so-called atmosphere and ocean de-aliasing level-1B (AOD1B) data product is based on atmosphere general circulation model, the operational ECMWF and the wind-driven barotropic ocean model for the current GRACE Level 2 data products, Release 04 and 05 (RL05). Previous studies have uncovered spurious jumps in the ECMWF in 2006 and 2010 due to changes in atmosphere circulation model parameterizations and have correlated these errors to potentially contaminate GRACE estimated mass change on Earth’s high altitude regions. In addition, studies have implicated the much larger errors in the atmosphere pressure fields over such regions as Antarctica ice-sheet, and thus the corresponding degradation of GRACE observed ice mass balance over this region. Here we study the effects of improved AOD1B data product, both in modeling that uses the reanalysis data product (ECMWF ReAnalysis-Interim, ERA-Interim) and in improved 3D modeling approach, on GRACE monthly gravity field inversion over regions such as Antarctica, Greenland and the world’s highest plateau, the Qinghai-Tibetan Plateau. We employ an improved Energy Balance Approach (EBA) to conduct GRACE inversion experiments to study the potential improvement in GRACE solutions using more accurate AOD1B regional or global data products.

Groundwater Depletion in North China from GRACE Satellites, Ground-based Monitoring Network and Groundwater Modeling

W. Feng1,2,3, M. Zhong1, J.M. Lemoine3, R. Biancale3, H.Z. Hsu1, J. Xia4, C.M. Zheng5, G.L. Cao5, Q.H. Tang6 1State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of

Sciences, 340 Xudong Road, Wuhan, 430077, P. R. China, Fengwei@whigg.ac.cn 2Graduate University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing, 100049, P. R. China

3CNES/GRGS, 18 Avenue E. Belin, Toulouse, 31401, France 4Research Institute for Water Security, Wuhan University, 8 Donghu South Road, Wuhan, 430072, P. R. China

5Center for Water Research, College of Engineering, Peking University, 5 Yiheyuan Road, Beijing, 100871, P. R. China 6Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 11A, Datun Road,

Beijing, 100101, P. R. China

Abstract Extensive anthropogenic activities in North China, such as agricultural irrigation and urbanization, are depleting the groundwater resource in the region at an alarming rate. Since its launch in 2002, the Gravity Recovery and Climate Experiment (GRACE) satellites have become a powerful tool to monitor regional groundwater storage change. This paper provides a detailed assessment of spatiotemporal variations of groundwater in North China, as estimated from three relatively independent methods, i.e., GRACE satellite measurements, ground-based well observations, and regional groundwater modeling. First we calculated the groundwater storage changes in the region by combining the time-varying gravity field data from GRACE with outputs from land-surface models. Besides the natural surface-water storage component, the effects of reservoir storage, coal transport and inter-basin water diversion in the region were also assessed and removed from GRACE-derived terrestrial water storage changes. The spatial pattern of GRACE-based groundwater depletion indicates significant water mass loss in the piedmont and central plain regions of North China. The ground-based monitoring well network also indicates that the water table in the piedmont regions of Taihang Mountains, the western part of North China Plain, declines faster than those in other regions of North China. This is in good agreement with the GRACE-based result. Then, we built a multilayer regional groundwater model to simulate the flow system in the North China Plain. Simulated groundwater depletion further confirms the GRACE-derived result, i.e., the large groundwater depletion rate exists in the piedmont region of North China. Global Hydrological Budget Derived from Atmospheric Circulation Model and GRACE Time-variable Gravity Data

Zizhan Zhang1,3 B. F. Chao2 Jianli Chen3 Yang Lu1 Houze Hsu1 1Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, China, zzhang@asch.whigg.ac.cn

2College of Earth Sciences, National Central University, Chung-Li, Taiwan, China 3Center for Space Research, University of Texas at Austin, Austin, USA

Abstract

To understand and be able to monitor the water mass balance is a most fundamental goal in global hydrological studies. Combining two independent global data sets--the time-variable gravity solution from GRACE and the water vapor content variation from an atmospheric general circulation model (AGCM) from ECMWF (European Centre for Medium-Range Weather Forecasts) or NCEP (National Centers for Environmental Prediction), we develop a simple methodology in forming a hydrological estimate for what can be interpreted directly to be the runoff R on land and freshwater dispersion D in ocean. We experiment with the data sets quantitatively and obtain R and D, in monthly maps for the 10-year period of 2003 to 2012

at a spatial resolution of about 300 km dictated by the quality of the GRACE data. The governing equation is: R (on land) or D (in ocean) = (P – E) – ΔσGRACE, where P – E is (monthly) precipitation minus evapotranspiration we derive from AGCM data, and ΔσGRACE is the (monthly) change in surface water distribution derived from GRACE data after undergoing a proper set of corrections; all these variables encompass all forms of water quantity under the respective names. The results in terms of the equivalent water thickness (EWT) show that time variable changes of traces and patterns of monthly fresh water discharge from continents, drainage basins and global land, which indicates that this method has important potential for monitoring of combined surface water and submarine groundwater as well as the dispersion of freshwater in ocean at near-real time at the said spatial resolution, as well as for contributing to contemporary global water balance studies and for constraining global hydrological model simulations. Lastly we also discuss the possible errors and potential utilities of such observables under present resolutions. Keywords: hydrological budget, runoff, dispersion, GRACE, atmospheric

Space Geodesy Techniques Application for the Natural Hazards Monitoring of the Russian Far Eastern Territory. (Review)

Suriya Tatevian1 Vladimir Timofeev2, A.A. Trofimuk2

1Institute of Astronomy, RAS, statev@inasan.ru 2Institute of Petroleum Geology & Geophysics, Russian Academic of Sciences

Abstract

Russian Far East has a complicate geological structure and tectonics because of convergence of three tectonic plates (Eurasian – EUR, North American – NAM and Pacific – PAC) and an existence of several independent microplates (Okhotsk – OKH, Amurian – AMU and Bering – BER). During the last 15 years GPS technique has been using for studying of the recent crustal velocities Russian Far East. The next conclusions have been made: • Recent crustal velocities of the northern part of Russian Far East are defined by the NAM-plate rigid rotation (western

part) and interaction with PAC-plate (eastern part). • There are GPS velocity boundary between continental part and Sakhalin Island. • GPS velocities of the south-east of Russian Far East referenced to EUR are small enough (less than 5 mm/yr, a median

value around 1 mm/yr) and are showing domination of the east component. They don’t correspond perfectly to well-known AMU- microplate rigid rotation model.

At present Russian Academy of Sciences realized a new geodynamic project: Recent geodynamics, active geologic structures and natural hazards of Russian Far East». The main objectives of the RAS-NASA agreement on cooperation in Space Geodesy application for the Solid Earth’s studies are joint efforts to strengthen the Global Geodetic Observing System's (GGOS) with the ground stations in Russia. In 2004, a new item has been included in the joint program, namely: -establishment and strongly supporting of the Asia-Pacific Natural Hazard Laboratory (A-PaNL) - as a component of the multinational Circum-Pacific geodetic monitoring network that could operate in real time. Tectonic Deformation & Occurrence of the Great Earthquakes Around the Bayan Har Block in Tibet Plateau, China

Jinwei Ren, Changyun Chen, Guojie Meng, Junlong Zhang, Panxin Yang, Chaozhong Hu, Jundong Fu, Renwei Xiong Institute of Earthquake Science, CEA, Beijing 100036, China, ren@seis.ac.cn

Abstract

The Bayan Har block is one of the most important geological units in the Tibet plateau. Almost all the large earthquakes (M>=7) occurred in the last 30 years in Tibet were located along the boundaries of the block. The crust movement of Tibetan plateau delineated by the GPS measurements shows that the material being penetrated eastward because of the collision between India plate and eastern Asia continent. The eastward flow is separated by several large left-lateral strike-slip faults. They are Xianshuihe fault, East Kunlun fault and Altyn-Tag fault which is the northern boundary of the Plateau. Once the movement of the blocks between the faults are obstructed, thrust faults would be created to accommodate the deformation that transferred by the strike slip motion along the faults. Longmenshan fault on which the Wenchuan earthquake occurred, is one of the thrust fault that accommodate the deformation transferred by the East Kunlun fault. Along the East Kunlun fault there were at least four large earthquakes with magnitude greater than 7 occurred since 1937 (figure 1). Namely, the Ms8.1 of Kunlun earthquake in 2001, the Ms7.0 of Alan earthquake in 1963, the Ms7.5 of Huashixia earthquake in 1937, and a great earthquake near Maqin which may took place several hundred years ago and created a clear surface ruptures along the eastern segment of East Kunlun fault around Maqin county in Qinghai Province, China. Field investigation shows that the surface ruptures created by these large earthquakes have gone through the whole East Kunlun fault, which means that the

East Knulun fault could not hold up the deformation any longer, and all the burden were transferred to Longmenshan fault. This might be the reason of the occurrence of Wenchuan earthquake. The movement of Longmenshan fault was dominated by the vertical motion during the Wenchuan Earthquake. GPS observations have successfully described the horizontal movement of co-seismic displacement of Wenchuan Earthquake, but fail to do so in vertical direction, because of the lack of continuous stations before the earthquake, especially in the west part of the fault. Deformation obtained from InSAR images are needed for describing the vertical deformation, but special attention should be paid to the error analysis when processing the SAR data to eliminate the effect of landslides which are almost continuously distributed along the Longmenshan fault. The east boundary of the Bayan Har block is the Longmenshan thrust along which the 2008 Wenchuan Ms8.0 earthquake has occurred. Although the horizontal compression across a single Longmenshan fault is only 2-3mm/a, the shortening between Bayan Har block and Chengdu basin is at a rate of about 10mm/a, the shortening deformation is distributed across the wide area of 300km west of Longmenshan.

Vertical Velocity Field for the Tibetan Plateau and Surroundings

Jeff Freymueller1, Shaomin Yang2, Qi Wang2,3, and Xuejun Qiao2 1Geophysical Institute, University of Alaska Fairbanks, USA, jeff.freymueller@gi.alaska.edu

2Institute of Seismology, China Earthquake Administration, Wuhan CHINA 3China University of Geosciences Wuhan, Wuhan CHINA

Abstract

We use the present-day rates of vertical motions from GPS sites across the Tibetan Plateau and the surrounding area, in concert with measurements of horizontal motions and other data, to study the causes of these motions. Many of the sites used for the velocity field are campaign GPS sites, because continuous sites are rare in Tibet, but many of the campaign sites have very long measurement histories. The campaign data require careful quality control, and estimates of vertical rates are more robust when spatial averaging can be done to identify outliers and reduce noise. Present-day vertical motions include components from long-term tectonic uplift or subsidence, deformation related to the earthquake cycle, shorter-term hydrologic (loading) deformation, and anthropogenic effects such as groundwater extraction. Glacial isostatic adjustment may also contribute, depending on the scale of glaciation at the Last Glacial Maximum and the viscosity of the mantle beneath Tibet. We estimate 6-8 mm/yr uplift in the High Himalaya and southernmost Tibet, decreasing to 2-3 mm/yr uplift in the Yarlung valley. The uplift peak agrees with earlier leveling observations in Nepal, and the uplift here is due mainly to interseismic strain from the locked Himalayan megathrust. We observe consistent subsidence across the region filled with lakes in central Tibet, which is in part due to increasing lake and/or groundwater loading. Based on the GPS observations and modeling of GRACE data, we conclude that hydrologic loading deformation is a significant component of the present-day vertical velocity field. In the north and northeast edges of the plateau, uplift in Altyn Shan and Qilian Shan is 3-5 mm/yr or more is associated with rapid convergence at the edges of the plateau. Elsewhere on the plateau, most sites show slow uplift rates on the order of 1-2 mm/yr, while some areas bounding the plateau, such as the Sichuan basin, show subsidence. The current GPS vertical velocity field in Tibet indicates that some published GIA models significantly overestimate present-day GIA uplift rates, which means that models featuring a large ice sheet covering Tibet during the last glacial maximum are not realistic.

Gravity and GPS Measurements at South-West Part of Baikal Rift Timofeev V.1, Ardyukov D.1, Stus Y.2, Timofeev A.1, Kalish E.2, Sizikov I.2, Nosov D 2.

1A.A. Trofimuk Institute of Petroleum Geology & Geophysics, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia, timofeevvy@ipgg.sbras.ru

2Institute of Automatic and Electrometry Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia

Abstract Measurenents of non-tidal variations of gravity (Δ g) which were obtained from 1992 to 2012 at the Talaya seismic station (located in the south-western part of the Baikal region), are interpreted together with GPS observation data which were obtained from 2000 to 2013 at the same station. The linear component of gravity variations corresponds to changes in the elevation of the site. The correlation coefficient is close to the normal value of the vertical gradient of gravity. At this site, coseismic gravity variations at the time of the Kultuk earthquake (27 August 2008, Mw = 6.3) were caused by a combined effect of the change of the site’s elevation and deformation of the crust. Our estimations of the coseismic effects are consistent with results obtained by modeling based on the available seismic data. Key words: monitoring of gravity variations, rift zone, GPS-monitoring, earthquake.

Preseismic Ionospheric Electron Enhancement, Revisited Kosuke Heki

Hokkaido University, Japan, heki@mail.sci.hokudai.ac.jp

Abstract Possible enhancement of ionospheric Total Electron Content (TEC) immediately before the 2011 Tohoku-oki earthquake (Mw9.0) has been reported by Heki [2011]. Critical responses to it often come in two stages; they first doubt the enhancement itself and attribute it to an artifact. Secondly (when they accept the enhancement), they doubt the significance of the enhancement among natural variability of space weather origin. For example, Kamogawa and Kakinami [2013 JGR] attributed the enhancement to an artifact falsely detected by the combined effect of the highly variable TEC under active geomagnetic condition and the occurrence of a tsunamigenic ionospheric hole [Kakinami et al., 2012 GRL]. Here we closely examine the time series of vertical TEC before and after the 2011 Tohoku-oki earthquake. We first demonstrate that the tsunami did not make an ionospheric hole, and next confirm the reality of the enhancement using data of two other sensors, ionosonde and magnetometers. The amplitude of the preseismic TEC enhancement is within the natural variability, and its snapshot resembles to large-scale traveling ionospheric disturbances (LSTID). However, distinction could be made by examining their propagation properties. Similar TEC anomalies occurred before all the M≥8.5 earthquakes in this century, suggesting their seismic origin. The content of this presentation is under review as Heki and Enomoto [JGR Space Physics].

GPS Approach Detecting Tsunami Energy Scales in Real-Time for Early Warnings Y. Tony Song

Jet Propulsion Laboratory, Pasadena, California 91109, USA, Tony.Song@jpl.nasa.gov

Abstract This talk reviews how tsunamis form from earthquakes and how GPS technologies can be used to detect tsunami energy scales in real time. Most tsunami fatalities occur in near-field communities of earthquakes at offshore faults. Tsunami early warning is key for reducing the number of fatalities. Unfortunately, an earthquake’s magnitude often does not gauge the resulting tsunami power. Here we show that real-time GPS stations along coastlines are able to detect seafloor motions due to big earthquakes, and that the detected seafloor displacements are able to determine tsunami energy and scales instantaneously for early warnings. Our method focuses on estimating tsunami energy directly from seafloor motions because a tsunami’s potential or scale, no matter how it is defined, has to be proportional to the tsunami energy. Since seafloor motions are the only source of a tsunami, their estimation directly relates to the mechanism that generates tsunamis; therefore, it is a proper way of identifying earthquakes that are capable of triggering tsunamis, while being able to discriminate those particular earthquakes from false alarms. Examples of detecting the tsunami energy scales for the 2004 Sumatra M9.1 earthquake, the 2005 Nias M8.7 earthquake, the 2010 M8.8 Chilean earthquake, and the 2011 M9.0 Tohoku-Oki earthquake will be presented. Related reference:

1. Xu, Z. and Y. T. Song (2013), Combining the all-source Green’s functions and the GPS-derived source for fast tsunami prediction – illustrated by the March 2011 Japan tsunami, J. Atmos. Oceanic Tech., jtechD1200201.

2. Song, Y. T., I. Fukumori, C. K. Shum, and Y. Yi (2012), Merging tsunamis of the 2011 Tohoku-Oki earthquake detected over the open ocean, Geophys. Res. Lett., doi:10.1029/2011GL050767.

3. Song, Y. T. and S.C. Han (2011) Satellite observations defying the long-held tsunami genesis theory, D.L. Tang (ed.), Remote Sensing of the Changing Oceans, DOI 10.1007/978-3-642-16541-2, Springer-Verlag Berlin Heidelberg.

4. Song, Y. T. (2007) Detecting tsunami genesis and scales directly from coastal GPS stations, Geophys. Res. Lett., 34, L19602, doi:10.1029/2007GL031681.

Effect of Topography on Coseismic Gravity Changes and Verification from GRACE Jin Li1, 2, Jianli Chen2

1Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, China, lijin@shao.ac.cn 2Center for Space Research, University of Texas at Austin, Austin, Texas, USA

Abstract

It is generally believed that horizontal coseismic deformations would not cause observable gravitational changes, as they do not introduce significant mass redistribution as evident as the vertical deformations do. However, the conclusions turn out to be different when the effect of topography is taken into account. Unlike the case of flat terrain (or crustal layers), an inclined surface (or interfaces) combined with horizontal coseismic deformations will lead to equivalent vertical displacements,

causing the Earth’s gravitational change. Generally, most large earthquakes occur in mountainous or oceanic trench regions with complex topography and steep slope. Hence, topographic effect associated with horizontal coseismic deformations of large earthquakes on gravity changes might not be negligible. This study proposes an approach to calculate the equivalent vertical displacements based on the dip angles of grid units from a DEM model, according to the predicted horizontal deformations by a dislocation model. Then we compute corresponding effect on coseismic gravity changes. In a case study of the 2011 Japan Tohoku-Oki earthquake, we demonstrate that the effect of topography is apparently non-negligible, and is at the same order of magnitude as the seawater correction, which has been extensively investigated in series of recent studies. We also analyze coseismic gravity changes retrieved from GRACE time-variable gravity data to verify the topography effect. Further more, we report some preliminary results of the Moho topographic effect on coseismic gravity changes.

Improved Constraints of Seismic Source Parameters for the 2011 March Tohoku-Oki Earthquake from GRACE Gravity and Gravity Gradient Change Measurements

Chunli Dai1, Lei Wang2, C.K. Shum1, Junyi Guo1, Kun Shang1

1Division of Geodetic Science, School of Earth Sciences, The Ohio State University, Columbus, Ohio, dai.56@buckeyemail.osu.edu

2Division of Seismology, Geology, & Tectonophysics, Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA

Abstract

A new approach of using north component of gravity change derived from the Gravity Recovery And Climate Experiment (GRACE) data is first shown to clearly reveal the seismic deformation following the March 2011 Tohoku-Oki earthquake with north-south stripes greatly reduced. Localized Slepian spectrum analysis verifies that the north component of gravity best matches the published dislocation model prediction compared to other components of gravity and gravity gradient. Significant north component of gravity change up to –17.6±0.6 µGal and gravity gradient up to 1.27±0.06 mE are produced, which agree well with model predictions. This improved-processed gravity data uncovers that the slip orientation rotates for about 10 degrees clockwise compared to the GPS/seismic slip models and the centroid location located west of GPS/seismic centroid locations.

Gravity Changes Caused by Crustal Movement in Tibet Region Fang Jian, and Liu Jie

Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, China, jfang@whigg.ac.cn

Abstract The geodetic and geophysical evidence of the uplift and crustal thicken of the Tibetan Plateau has been presented by using gravity, GPS and level observations in past teens years. In this paper, we investigate tectonic deformation using 10years GRACE and GPS long period trend data, meanwhile taking the GIA and water storage effect into account. After deduct GIA and water storage effect, the 10years GRACE data shows gravity rise 4ugal in central part of Tibet. We consider this gravity change caused by mass increase of Tibet crust due to Indian plate collision. We give a crust uplift 1.1mm/year model can well explain the gravity change, and the model is good agreement with GPS observations in these years.

Study on Deformation of Wenchuan Earthquake by D-InSAR Based on ERA-Interim Data and NeQuick Model

Yan-Ling Chen, Qi-Ming Chen, Cheng Huang, Shu-Li Song, Xiao-Ya Wang Shanghai Astronomical Observatory，Chinese Academy of Sciences, Shanghai, China, ylchen@shao.ac.cn

Abstract

Atmosphere delay including tropospheric and ionospheric delay is relatively large error sources for Differential Interferometric Synthetic Aperture Radar (D-InSAR). In order to remove this kind of error we processed Wenchuan ALOS PALSAR images using ROI_PAC software and corrected the atmospheric delay through ERA-Interim data from ECMWF（European Centre for Medium-Range Weather Forecasts and NeQuick model. And then we compared InSAR sedimentation with GPS deformation observations to validate the effect of ERA-Interim data and NeQuick model, further provide the feasibility of meteorological data and numerical model during the study of atmospheric effect elimination of InSAR.

GPS Velocity field and Rheology Parameters for Altay-Sayan Region. Timofeev V., Ardyukov D., Timofeev A.

A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia, timofeevvy@ipgg.sbras.ru

Abstract This report deal with the modern geodynamic situation and crustal stress state of Altay-Sayan region. Modeling results of displacement fields (coseismic, postseismic and tectonic) are dependent on elastic modulus and viscosity parameters of the medium. Estimation of elastic modulus was developed by geodesy measurement of seasonal effect loading at Sayan-Shyshi hydro-electric station reservoir. Elastic modulus was used for coseismic effects modeling for Sayan earthquakes (10/02/2011, M = 5.4 and 27/12/2011, M = 6.7). GPS result (2004-2012 yy.) for postseismic situation at Chuii earthquake zone (27/09/2003, M = 7.5) was used for study viscosity parameters of lower crust. Results of GPS observation of Altay-Sayan region (2000-2012 yy.) allow to value tectonic velocity field of Altay-Sayan region at south boundary of Siberian platform. Key words: GPS-monitoring, leveling, earthquake, elastic modulus, viscosity modulus, Altay-Sayan region of Siberia, modeling of coseismic and postseismic effects.

Tectonic Plate Boundaries at East Russia by Geophysical Data. Timofeev Va, Ardyukov D1, Timofeev A1, Stus Y 2, Kalish E 2, Gornov P3, Sizikov I 2, Kulinich R 4, Valitov M4, Ducarme B 5

1A.A. Trofimuk Institute of Petroleum Geology & Geophysics, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia, timofeevvy@ipgg.sbras.ru

2Institute of Automatic and Electrometry Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia 3Yu.A. Kosygin Inst. of Tectonics & Geophysics, Far Eastern Branch Russian Academy of Sciences, Khabarovsk, Russia

4V.I. Il'ichev Pacific Oceanological Institute Far Eastern Branch of Russian Academy of Science, Vladivostok, Russia 5Catholic University of Louvain, Georges Lemaître Centre for Earth and Climate Research, Belgium

Abstract

The Tohoku-Oki earthquake of 11 March 2011 Mw = 9.0 description are presented in many article. We tried to measure coseismic displacement and gravity effect at south part of Primorye territory (Russia) at 1000 km distance from the epicentre. Some GPS results measured during last years at Far East Russia continental coast are investigated. Joint project to measure gravity change associated with tidal and earthquake's effect using absolute and relative gravimeters was started at 2010 year. In this work the results of complex gravity observation developed at Shults Cape of Gamov peninsular (42.58°N, 131.15°E, Russia) are presented. Absolute laser gravimeter GABL type and Scintrex type relative gravimeter were used for measurement. Preliminary estimate of gravity effect induced by the Tohoku-Oki earthquake of 11 March 2011 Mw = 9.0 at Primorye territory (Russia) are presented. For calculation of tidal correction we compared the observed tidal parameters of the main tidal waves O1 and M2 with modelled ones computed from nine different ocean tidal models: GSR3, GSR4, FES95, FES02, FES04, GOT00, NAO99, ORI96 and TPX06. Theoretical model based on TPX06 ocean tides model and DDW99 non hydrostatic body tides model was used for tidal correction in absolute gravity data. Coseismic gravity effect was discussed (5.1 ± 2.0 µGal, change from 2010 to 2011-2012). Coseismic crustal displacements revealed by GPS data at Far East Russia continental coast are also presented. Keywords: absolute gravimetry and GPS, tidal gravity model and observation with Scintrex gravimeter, coseismic effect for Tohoku-Oki earthquake.

Estimating Parameters of Subsurface Structures from Airborne Gravity Gradiometry Data Using a Monte-Carlo Optimization Method

Sibel Uzun and Christopher Jekeli Division of Geodetic Science, School of Earth Sciences, Ohio State University, Columbus, OH, uzun.1@osu.edu

Abstract

The inverse problem of estimating parameters of subsurface structures can be considered as an optimization problem where the parameters of a constructed forward model (gravitational model) are estimated from gravimetric observations collected on or above the Earth’s surface by minimizing the difference between the predicted model and the observations. This problem could be solved by traditional techniques such as the iterative Least-Squares Solution, or by innovative methods such as random search techniques. This study presents a Monte-Carlo optimization method called Simulated Annealing (SA) to estimate the parameters of subsurface structures from airborne gravity gradient measurements. This technique is implemented for the case of estimating dip angle and vertical displacement (throw) of a fault, both simulated and in a real field. In the simulation, a comparison of results is presented for the SA algorithm and the Least-Squares solution (LESS) within the Gauss-Helmert Model. It is shown that the SA algorithm is as stable as LESS, for various noise levels in the observations. For the estimation of the real fault parameters, it is shown that the SA algorithm provides very good estimates of the dip angle and the throw parameters. Thus the SA algorithm is a robust inversion technique that may be applied to the geophysical inverse problem using gravity gradients.

Regional Sea-Level Variations Around Taiwan Wen-Hau Lan1, Chung-Yen Kuo1, Li-Ching Lin2, C.K. Shum3

1Department of Geomatics, National Cheng Kung University, Tainan, Taiwan, p68001021@mail.ncku.edu.tw, 2Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan,

3Division of Geodetic Science, School of Earth Sciences, Ohio State University, Ohio, USA,

Abstract In recent decades, global warming induced global sea-level rise has resulted in societal and human coastal vulnerability in the world’s deltaic regions and for island nations. Taiwan is an island country and similar to many countries, the main population and the developed cities are mostly located near the coasts. Comparing to the other countries, global sea-level rise has a relatively significant impact on Taiwan, primarily because of large land vertical motions induced with tectonic origin, sediment load or erosion. Accurate estimation of long-term sea-level changes and investigation of the primary contributions causing sea level rise around Taiwan are of importance, such that one could provide a more accurate projection over the next century and beyond. In the study, we will determine sea level change using long-term (over 100 years) tide gauge records and multi-mission multi-decadal (~20 years) satellite altimetry data around Taiwan. Since tide gauge records principally contain the signals of crustal vertical motions, we compute vertical crustal motions using the differences of sea level measurements from satellite altimetry and tide gauges. In addition, our goal is to characterize the contributions of sea-level changes around Taiwan using a combination of in-situ hydrological data, GRACE temporal gravity field inferred mass transport, and reconstructed sea-level change from data and ocean model.

Global Mean Sea Level Rise Analysis and Prediction by Using singular Spectrum Analysis Yunzhong Shen1,2 , Yingchen Ao1 , Yi Chen1

1College of Surveying and Geo-informatics, Tongji University, Shanghai, China, yzshen@tongji.edu.cn 2Center for Spatial Information Science and Sustainable Development, Tongji University, Shanghai, China

Keywords: Global mean sea level change; Singular spectrum analysis; Sea level rise prediction; Uncertainty

Abstract

Global mean sea level (GMSL) rise is an important issue of global changes; however the predicted GMSL in 2100 is of great uncertainty. By using the reconstructed GMSL time series from 1880 to 2009 by Church and White (2011) and the GMSL time series from 1993 to 2013 derived by satellite altimetry (http://sealevel.colorado.edu/), this paper analyzes the characteristics of GMSL rise and predicts the GMSL until 2100 using Singular spectrum analysis (SSA), since SSA is a powerful tool for analyzing short, chaotic time series or dynamic process. We first compute an offset between the two GMSL time series according to common data period from 1993 to 2009, and then combine the two time series together to form an entire time series from 1880 to 2013. There are total 1597 monthly mean sampling data in the combined time series. By using the window length of 600, we form the 600×998 trajectory matrix and then the 600×600 covariance matrix. The principle component analysis is applied to decompose the covariance matrix into Principle Components (PCs) and correspondent eigenvectors. The first 27 PCs are taken as the signals of GMSL changes and the rest PCs are the noises. The first 2 PCs represent the trend of GMSL change, which is about 1.60mm/yr. The rest 25 PCs are the oscillations, among which 5 pairs of PCs (namely, 5-6, 7-8, 16-17, 24-25, 26-27) are the harmonic terms, the correspondent periods are about 20, 10, 2, 1.2 and 3 years. With 27 PCs and the eigenvectors, we construct the linear recurrent formula, and then reconstruct the GMSL time series. The residuals of the original the GMSL time series minus the reconstructed time series are shown as random noise; its estimated variance is about 20mm. The predicted GMSL rise using the linear recurrent formula is 220.8 mm from 2013 to 2100, and the uncertainty is estimated to be 94.2 mm using Monte Carlo simulation according to the estimated variance. Nevertheless, the GMSL rise is about 283.6 mm from 2013 to 2100, if only the trend term, i.e. the first 2 PCs.

Study on Changes of Mean Sea Level at Dagang Tidal Gauge (Withdraw) Fumei Wu, Yingchun Li, Ziqing Wei

Xi’an Research Institute of Surveying and Mapping, 710054, China, wfm9431812@163.com

Abstract “1985 National Height Datum” was defined by the mean sea level at Dagang tidal gauge, which was determined by averaging 10 mean sea levels of 19 year period by using 1952~1979 tidal data. In order to investigate the stability of the 1985 National Height Datum, we have studied the changes of the mean sea level by analyzing 1980~2003 tidal data at Dagang gauge. First the frequencies of main tides are gained by wavelet transform and Fouirer transform. Then the amplitude and phase of main tides are obtained by harmonic analysis. Next the changes of the mean sea level during the period of 1980 to 2011 are studied. And at last the height of the mean sea level at Dagang tidal gauge in this period is achieved by lowpass filtering.

Regional Mean Sea Level Study for the Arctic Ocean based on Multi-mission Satellite Radar Altimetry and Long-term Tide Gauge Data

Junkun Wan1, C.K. Shum1, Chungyen Kuo2, Junyi Guo1, Kuo-Hsin Tseng1, Yuchan Yi1, Zhenwei Huang3 1Division of Geodetic Science, School of Earth Sciences, The Ohio State University, wan.70@osu.edu

2Department of Geomatics, National Cheng Kung University 3Chinese Academy of Surveying and Mapping, Beijing

Abstract

The Arctic Ocean is undergoing substantial changes as a result of climate change. It is of interest to observe Arctic Ocean sea-level rise, understand its geophysical causes and quantify the difference of Arctic sea-level rise from global sea-level rise for better understanding of drastic climatic changes in the Arctic Ocean. However, previous altimetry sea-level studies indicate a wide range of contemporary sea-level trend estimates for the Arctic Ocean, from 0.7 mm yr-1 to 3.6 mm yr-1. The errors in the altimetry observed sea-level trend for Arctic region is at 1.3 mm/yr while that for global sea-level rise is only at 0.5 mm/yr. This is not only because the coverage of TOPEX-class altimetry satellites is bounded to within ±66° in latitude, but also due to the quality of altimetry data highly influenced by the existence of sea ice in the Arctic Ocean. Here we further reprocessed multiple satellite altimetry data, ERS-1/-2/Envisat, GFO, and including Cryosat-2 and SARAL/Altika, to estimate the rate of contemporary Arctic region sea-level rise. The influence of models for geophysical and media corrections, such as ocean tides, dynamic ocean response from atmosphere, media (troposphere and ionosphere), mean sea surface model for gradient corrections, contamination over sea-ice covered ocean for altimetry data has also been investigated. Furthermore, we merged sea level variations observed by different satellite mission by removing geographically correlated relative biases between different altimeter sea-level records with respect to the lower latitude observing but more accurate radar altimeter systems, including TOPEX/POSEIDON and Jason-1/-2. Altimetry data spans are still too short to fully mitigate inter-annual or longer oceanic variations. Here we will estimate mean sea level trends using the available tide gauge records and provide its uncertainty by comparing with short-term satellite altimetry and an ensemble of latest glacial isostatic adjustment (GIA) models to account for tide gauge crustal motions due to GIA. Our final result is a preliminary estimate of the contemporary sea-level rate and its error within the Arctic Ocean using satellite altimetry and tide gauge records.

The GGOS Global Space Geodesy Network and its Evolution. Michael R. Pearlman1, Erricos C. Pavlis2, Chopo Ma3, Carey Noll3, Ruth Neilan4, David Stowers4, Scott Wetzel5, and

Stephen Merkowitz3 1Harvard-Smithsonian Center for Astrophysics, Cambridge MA, United States, mpearlman@cfa.harvard.edu

2University of Maryland, Baltimore MD, United States, 3NASA Goddard Space Flight Center, Greenbelt, MD, United States

4Jet Propulsion Laboratory/Caltech, Pasadena CA, United States, 5Honeywell Technology Solutions, Inc, Lanham MD, United States

Abstract

The improvements in the reference frame and other space geodesy data products spelled out in the GGOS 2020 plan will evolve over time as new space geodesy sites enhance the global distribution of the network and new technologies are implemented at the sites thus enabling improved data processing and analysis. The goal of 30 globally distributed core sites with VLBI, SLR, GNSS and DORIS (where available) will take time to materialize. Co-location sites with less than the full core complement will continue to play a very important role in filling out the network while it is evolving and even after full implementation. GGOS through its Call for Participation, bi-lateral and multi-lateral discussions and work through the scientific Services has been encouraging current groups to upgrade and new groups to join the activity. Simulations examine the projected accuracy and stability of the network that would exist in five- and ten-years time, were the proposed expansion to fully materialize by then. Over the last year additional sites have joined the GGOS network, and ground techniques have continue to make progress in new technology systems. This talk will give an update on the current expansion of the global network and the projection for the network configuration that we forecast over the next 10 years including the NASA Space Geodesy Project, which will support GGOS.

Preliminary Results of the 2013 SHAO Realization of Terrestrial Reference Frame and Earth Orientation Parameters

Bing He, Xiaoya Wang, Xiaogong Hu, Qunhe Zhao Shanghai Astronomical Observatory, 80 Nandan Road, Shanghai 200030, China, hebing@shao.ac.cn

Abstract

The Terrestrial Reference Frame (TRF) and Earth Orientation Parameters (EOP) with high accuracy is the basis for

geodesy,satellite navigation technique,astronomy, etc.A new realization of the global Terrestrial Reference System and correspanding Earth Orientation Parameters was finished at Shanghai Astronomical Observatory(SHAO) based on the space geodetic techniques VLBI,SLR,GNSS and DORIS.The input data used are time seris of SINEX files containing weekly solutions or session-wise NEQ of station positions and daily Earth Orientation Parameters determined by four techniques.To ensure the stability and reliability ,the input data span many years as long as possible.To define an underlying TRF sensed by those four techniques,proper constraints are applied to the unconstrained equation systems stacking from input data. Earth Orientation Parameters are used both as the input data in SINEX files and as the output combination parameters of four techniques.On the one hand,EOP are used as one kind of ‘global tie’ between four techniques to ensure and verify the consistency of the combined TRF.On the other hand ,the output EOP results , as the combination product of four techniques ,are in high agreement with the combined frame.We apply the variance component estimation method both when we decide the weight of every single SINEX input and when we decide the weights of different techniques during combination. Finally, we evaluate the accuracy of our TRF and EOP results based on ITRF2008 and IERS EOP C04. The statistical root mean squares of the difference between our EOP results and EOP C04 are better than 0.05mas for polar motion components and better than 0.03ms for UT1-TAI and LOD .

Activities at SHAO iGMAS Analysis Center Shuli Song, Qinming Chen, Junchen Xue, Weili Zhou, Xiaoya Wang, Xiaogong Hu, Zongyi Cheng, Wenyao Zhu

Shanghai Astronomical observatory, CAS, 20030, China, slsong@shao.ac.cn

Abstract With the Multi-GNSS development, to ensure the service quality, consistent with common open signals performance parameters, and realize the goal of interoperable GNSS open signals, the subgroup on international GNSS monitoring and assessment was formed at ICG-6 to monitor and assess GNSS open services worldwide. China is developing the international GNSS Monitoring and Assessment System (iGMAS) to support the activities for international GNSS monitoring and assessment. The data Analysis Center(AC) is one of the important part of iGMAS to process GPS,Galileo,GLONASS,COMPASS data from global tracking stations. In Shanghai Astronomical Observatory (SHAO), one of the iGMAS ACs was built which will produce satellite orbit, clock correction, ERP, station coordinates, atmosphere and ionosphere parameters, DCB, integrity parameters and so on. At present, the precision of most of these products of GPS,GLONASS are close to the results from IGS. The COMPASS data from iGMAS and MGEX tracking stations are analyzing in more detail.

Satellite Clock Error Prediction Based on ARIMA Weili Zhou

Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China, wlzhou@shao.ac.cn

Abstract In Global Navigation Satellite System(GNSS), the satellite clock error has to be modelled and predicted in order to broadcast the time parameter to final users. At present, the satellite clock error prediction in one-day length has to be provided each 6 hours by IGS with 3 ns precision. In order to increasing the clock error prediction for all satellites, the real time productions are used as the base sequence, and preprocessed with fitting and interpolation. Based on Autoregressive Integrated Moving Average Model (ARIMA), the satellite clock error is predicted. Meanwhile, the relationship between the length of base sequence and the forecast accuracy is analyzed. The results show that the appropriate selection of basic data series, such as 3 days, can realize the satellite clock error high precision prediction. Compared with the IGS prediction, the precision is improved to some extent.

A Functional Expression for Vertical Profile of Zenith Tropospheric Delay (Withdraw) Jingyang Zhao1,2, Shuli Song1, Wenyao Zhu1

1Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China, zhaojingyang@shao.ac.cn 2University of Chinese Academy of science, Beijing 100049, China

Abstract

The tropospheric delay is one of the most significant error sources for radio space geodetic techniques. There are a variety of defects for existing tropospheric delay models (such as Hopfield model, Saastamonion model, UNB models, etc.) that can’t meet the requirements of real-time positioning and navigation users. A deep understanding about the characteristics of tropospheric delay will greatly improve the establishment of models. Based on the vertical profiles of zenith tropospheric delay (ZTD) derived from ERA-Interim reanalysis data in 2005, as well as it’s hydrostatic and non-hydrostatic components (ZHD and ZWD), this paper presents a new functional expression for the height profile of zenith tropospheric delay. The functional expression is theoretically built on the variation of water vapor in the atmosphere, and represents ZTD, ZHD and

ZWD as a piecewise function respectively. The accuracy of the functional profile was assessed carefully. In contrast to the accuracy of UNB3m model, we also tested it with the ZTDs coming from 110 IGS (International GNSS Service) stations distributed all over the world. The functional expression has been found capable of closely matching any local zenith tropospheric delay vertical profile, and water vapor contained in the atmosphere is the key influence factor for its accuracy. The detailed results are as following: The deviations between the piecewise functional and the integral ZTDs and ZWDs are around 1cm at all 1.5-degree grid nodes, while that between the same two ZHD data sets are no more than 4 mm. The accuracy performance is relatively consistent over the range of 50 km high. The piecewise functional and IGS ZTDs comparisons at 110 stations show a mean difference of 0.07 cm in a year with a RMS of about 3.48 cm, which provides a significant improvement than UNB3m model. The functional expression we constructed will have important application value to the modeling of tropospheric delay.

Global Ionospheric Modeling with International Reference Ionosphere Constraint (Withdraw) Cheng Wang

PhD Visiting Scholar, Miami University, Oxford, Ohio; PhD Candidate, College of Surveying and Geo-Informatics, Tongji University, China, wangc9@miamioh.edu

Abstract

The ionosphere is a region of the earth’s upper atmosphere, extending from about 60 kilometers to several thousand km altitude. It is ionized by solar radiation and cosmic radiation. Ionosphere TEC is an important parameter for both satellite navigation and scientific studies of the ionosphere. For satellite navigation receiver designers, TEC determines the first order ionosphere induced range error, which is a dominant error source in GNSS generated navigation solutions. For ionosphere researchers, TEC describes the background state of the ionosphere. The Klobuchar model which is a currently available ionosphere correction model that whose parameters broadcast from the GPS satellites could only correct about 50% of the total ionospheric delay (Klobuchar, 1987). For these reasons, there are a number of GNSS networks whose main task is to provide measurements to allow assimilation of TEC maps (Giorgiana De Franceschi, 1998; Sakai, 2007; A.B.O. Jensen, 2008; S. Lejeune, 2012). There are four prominent IGS Ionosphere Associate Analysis Centers (IAACs) that have been generating global TEC maps for over one decade. They are the Center for Orbit Determination in Europe(CODE), European Space Operations Center of ESA(ESOC), Jet Propulsion Laboratory(JPL), and Technical University of Catalonia(UPC) (University of Bern, 2012; Schaer, 1999). An optimized method for global ionospheric modeling with international reference ionosphere constraint is proposed. It constrains total electron content of ionosphere over the equatorial anomaly area, southern hemisphere and the area where the value of total electron content calculated by general model is negative. The vertical total electron content is modeled in a solar-geomagnetic reference frame using a spherical harmonics expansion up to degree and order 15. The standard deviation of unit weight derived from processing is about 1.6 TECU. The proportion of absolute residual errors which less than 3 TECU achieves above 90%. Global ionosphere maps have a good agreement with IGS, and the RMS of difference is 3.7TECU around. The difference of satellites differential code bias is just about 0.1ns compared with CODE, as well as 0.2ns compared with IGS. The difference of receivers differential code bias is about 1ns (mostly 0.5ns) compared with CODE, as well as 1.5ns compared with IGS. The results indicate that global ionosphere model with international reference ionosphere constraint ensures the values of total electron content all over the globe are positive, and enhances total electron content precision of ionosphere over equatorial anomaly area, ocean and southern hemisphere.

Integral Formulas for High-order Radial Derivatives of a Harmonic Function (Withdraw) Ziqing Wei

Xian Research Institute of Surveying and Mapping, Xian 710054, China, ziqingw@sina.com

Abstract Following the approaches to deriving the radial derivative of a harmonic function in Heiskanen and Moritz (1967), the higher-order radial derivatives of a harmonic function are deduced. Several useful equations are obtained, and based on the equations, up to fourth-order radial derivatives of the gravity anomaly are developed.

Vertical Deformation Error Level Estimation of GPS and Loading Models Haoming Yan1, Yaozhong Zhu1, Wu Chen2

1State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences，Wuhan 430077，China, yhm@whigg.ac.cn

2Department of Land Surveying and Geo-Informatics, Hong Kong Polytechnic University, Hong Kong, China.

Abstract

Long-term continuous Global Positioning System (GPS) observations have become an important tool for studying the various geodynamic processes. To fully study the geodynamic processes at GPS stations, the vertical deformation error level must be estimated for both GPS observations and various loading models. By using three cornered hat method, we estimate the vertical deformation error level from GPS observations, geophysical fluid models, and GRACE data. We found that the vertical deformation error levels are 2.9±0.9mm and 2.5±0.6mm for GPS observations and GRACE results, respectively, which is greater than 1.3±0.7mm of geophysical fluid models result. Using this vertical deformation error level as criteria, we found that the 69% of the vertical deformation variance of GPS stations can be explained by GRACE results, and 72% (99%) of the annual vertical deformation amplitude (phase) of GPS stations can be explained by GRACE results. Furthermore, we also found that some systematic errors are still retained in the GPS vertical deformations time series, even the vertical deformation caused by geophysical fluid loading are best removed by using GRACE data. Key words: vertical deformation, error level, GPS, loading, GRACE

Chandler Excitation and Temperature Changes on Earth Leonid Zotov

Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia, wolftempus@gmail.com

Abstract The origin of the Chandler wobble and its amplitude changes is one of the open questions in the Earth sciences. This resonant polar motion should have been damped over a characteristic time of ~50 years, if there is no excitation, supporting it. According to the currently accepted point of view the excitation is provided by the ocean and atmosphere. Using specially developed Panteleev’s corrective filter we reconstructed geodetic excitation for the Chandler wobble on the interval of ~150 years. We found out that its amplitude modulations are synchronous with the 18.6-year cycle of the Moon orbital nodes regression. A wide interest of the Earth scientists is attracted to the Climate Change. The Earth global mean surface temperature (GMST) increased by ~ 0.7o in ~150 years, what is supposed to be related to the greenhouse effect and anthropogenic influence. But other oscillations are superimposed on this trend. Results of Singular Spectrum Analysis (SSA) of the HadCRUT3 GMST time series show presence of quasi-periodic temperature variations of 10, 20, 65 years periods. Already Lambeck in his book about Earth rotation (1980) pays attention to the similarity between the temperature variations and Earth rotation velocity (LOD) changes. We additionally found out that SSA-extracted quasi-20-year temperature component behaves similar to the Chandler excitation envelope. Thus, an external factor can exist, which influence atmospheric and oceanic circulation at this period, what is reflected in the Chandler excitation and temperature changes on Earth.

Monitoring Meteotsunami Using GPS Buoys Hong-Zeng Tseng, Ruei-Jing Lin, Chung-Yen Kuo, Kai-Wei Chiang, Li-Ching Lin, Kai-Chian Cheng

Department of Geomatics, National Cheng Kung University, Taiwan, hztseng@mail.ncku.edu.tw

Abstract Global Positioning System (GPS) buoys have been demonstrated to effectively and economically collect sea level data. By comparing to traditional tide gauge records, 1-100 Hz GPS records can measure high-frequency oceanic signals with periods of a few seconds to a few minutes; for example, meteotsunami and significant wave height that cannot be detected from 6-minite tide gauge records. In this study, two GPS buoys were deployed inside and outside the An-ping harbor, Tainan, with an additional GPS receiver on shore as a reference station. Different softwares including GravNav, RTKLIB, and GAMIT/TRACK were used to process GPS buoys measurements, with Differential GPS (DGPS) and Precise Point Positioning (PPP) techniques and using the precise ephemerides of the final product provided by International GNSS Service (IGS). By comparing the GPS buoys positioning results derived using different softwares with An-ping tide gauge records, the Root Mean Square (RMS) of differences between tide gauge records and DGPS solution is 3~10 cm and is 7~12 cm when PPP solutions is used. Finally, inside and outside of harbor GPS buoy derived sea level variations are decomposed into Intrinsic Mode Functions (INFs) by Hilber Huang Transformation (HHT) and the frequency of meteotsunami is successfully detected. After comparing the records of inside and outside GPS buoys and the computation of periods due to harbor resonance, meteotsunami is not amplified by harbor resonance in this area.

Relative Positioning of the Lunar Lander-Rover Using VLBI Techniques

Peijia Li, Yong Huang Shanghai Astronomical Observatory, 80 Nandan Road, Shanghai 200030, China, pjli@shao.ac.cn

Abstract

As the first spacecraft of the second phase of Chinese Lunar Exploration Program, Chang’E 3(CE-3) mission is scheduled for launch on Dec. 2013, which will execute a soft landing on the lunar surface and release a rover for the land survey explorations. In order to determine the relative position of CE-3’s Lunar Lander and Rover, a kinematic statistical method was proposed. This method uses both ranging and same beam VLBI measurements between the lander and rover for a continuous arc, combing with precise knowledge about the motion of the moon as provided by planetary ephemeris, to estimate the lander-rover relative positions on the lunar surface with high accuracy. For the traverse determination of the moving Lunar Rover, a method using the integration of delay-rate data was also investigated, and it showed a higher precise positioning results than the point positioning method, which provided a wide application of the VLBI data.

Leveraging Satellite Models to Support Temporal Gravity Investigations (Withdraw) J.N. Markiel, S. Ingalls

National Geospatial-Intelligence Agency, JN.M.Markiel@nga.mil Abstract

Accurately modeling temporal changes in the gravity field of the Earth is now a central concern of modern geodesy. Investigations in temporal gravity are currently the focus of considerable research on a global basis as reported by the IAG, Commission 2.2: Gravity Field [IAG, 2011]. These large scale investigations utilizing the GRACE/GOCE satellite datasets have demonstrated considerable time dependent variations in gravity as the result of mass changes, most notably owing to variations in water/ice regimes. However, these gravity missions are relatively recent, and so the length of the temporal period is limited to sub-decadal extent. Similarly, the long wavelength resolution of the satellite data precludes the derivation of a spatially dense, localized gravity model. The analysis of gravity changes on a localized basis is quite limited owing to the lack of quality gravity collections over a period of decades. Investigations over decadal time periods are accordingly unique. Detailed investigations of terrestrial gravity must include a number of superimposed effects; one of the most difficult to model accurately is the water table effect. It is generally critical to remove this effect to identify the residual gravity anomalies of interest; water table effects are often a degree of magnitude (or more) larger than the signal of interest. Utilizing sophisticated hydrologic models, it is possible to model the ground water and attendant soils; the results can then be leveraged to remove the water table effects and improve modeling of the residual anomalies. One critical question: does removal of the water table effect introduce a modeling bias to the residual gravity model? Are we removing the water table effects appropriately in terms of magnitude and direction? By leveraging satellite models, it is possible to validate the trend of the water table effect and support the temporal gravity modeling process. In this presentation, we update the results of our 2012 investigations at Long Valley Caldera, California, USA with respect to localized temporal gravity changes. Recent improvements to the original report include improved modeling of gravity changes due to water table effects, resolution of the heretofore misunderstood instrument bias, and improved gravity modeling techniques. Additionally, we compare the recent localized gravity model with the GRACE/GOCE gravity signature and analyze the correlation between the local and global models.

GRAV-D: Blending Satellite, Airborne and Surface Gravity Data for an Optimal Combination (Withdraw) D.R. Roman, V.A. Childers, M. Youngman, S.A. Holmes, Y.M. Wang & X. Li

Abstract

Aerogravity has been collected by NOAA's National Geodetic Survey as a part of the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) Project for about five years now. These data are nearly 25% complete for the Project and have become increasingly refined through several improvements in the underlying Newton software. These products are available on line along with associated documentation related to collection and processing by region. This discussion will focus on the programmatic aspects of collection as well as practical aspects of refining the data sets into useful products for incorporation with satellite gravity field products. It will wrap up with a discussion of near- and intermediate-term goals for GRAV-D both for collection and model development.

Alaska Geoid Improvements by Using Satellite and Airborne Information (Withdraw) X. Li, D.R. Roman, and S.A. Holmes

Abstract

Geoid modeling over Alaska, USA and northwestern Canada is technically challenging. The region features (1) a complex terrain that includes the two highest mountains in North America, Mount McKinely (20,320ft) in Alaska and Mount Logan (19,541ft) in the Yukon Territory and six major mountain chains; (2) a dynamic geology characterized with strong tectonic movement, significant post glacial rebound and ice melting; (3) inhomogeneous and sparse surface gravity data collected

over a span of a century. This study uses the newest satellite models and airborne data to improve the determination of, and better understand the accuracy of the geoid model in this region. First, the low to middle degree components of satellite-only global gravity models are used to reflect the long wavelength geology signals of the geoid. Second the tailored spherical harmonic approach is applied to improve the global geopotential model such as EGM2008 in the middle to high frequency band. Finally the existing GPS-Leveling data are analyzed to detect and reduce the crustal motion effect and systematic errors. They are used to infer the accuracy of the geoid model.

POSTERS

Establishing the Absolute Calibration for Multiple Satellite Altimeters in Taiwan Ting-Yi Lin1, Chung-Yen Kuo2, Hong-Zeng Tseng2, Kai-Chien Cheng3

1Graduate Institute of Applied Geophysics and Environmental Sciences, National Chung Cheng University, Taiwan (locklockr2002@gmail.com)

2Department of Geomatics, National Cheng Kung University, Taiwan 3Department of Earth and Environmental Sciences, National Chung Cheng University, Taiwan

Abstract

In the recent decades, satellite altimetry has become one of the main Earth observing tools to monitor sea surface height (ssh) and its change. Due to its capability of collecting the global ssh in the cm-level, satellite altimetry has been the main contributor to studies of global mean sea level rise. However, in order to get absolute ssh, the bias and the drift between the measured ssh and the truth need to be accurately resolved. In this study, an absolute calibration site is established off the coast of Chiang Chung, Taiwan for Envisat and its successor AltiKa. A GPS ship and a GPS buoy were utilized to survey the mean sea surface gradient. As the result, the tide gauge in Chiang Chung can be used to provide a time series of ssh to be calibrating with the Envisat/AltiKa ssh. The result of this calibration site is useful in the Taiwan surrounding ocean and contributing to the international collaborating effort toward the AltiKa mission. Keyword: Sea Surface Height, Satellite Altimetry, Absolute Calibration

Gravity Changes Over Russian Rivers Basins from GRACE Leonid Zotov1, Natalya Frolova2, Maxim Harlamov2

1Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia 2Department of Hydrology, Faculty of Geography, Lomonosov Moscow State University, Russia

Abstract

GRACE twin-satellites provide monthly data upon the gravitational field of the Earth since 2003, what presents a big interest for hydrological studies. Gravity data reflect changes, related to the groundwater redistribution, ice melting, and precipitation accumulation.

We use Multichannel Singular Spectrum Analysis to filter GRACE data and separate the principal components (PCs) of different periods. The obtained animated maps of PCs are useful for seasonal and long-periodic gravity changes study. Data averaging over the large river basins of Russia was performed. The obtained curves can be compared to the hydrological models, such as GLDAS or WGHM.

By spring 2013 an extremely large snow accumulation occurred in Russia. Melting of this snow induced large floods and river levels increase. The exceptional maxima are well seen in the curves obtained from GRACE.

Speaking about long-periodic climate-related changes, they are different for the basins of European and Siberian rivers. Overall trend represents maximum in 2009, following by slow decrease. Possible reasons of this are discussed. Acknowledgements: This work is supported by the RFBI grant N 12-02-31184 and IAG travel grant.