measuring atmospheric changes in the arctic christopher j cox university of idaho, geography

Measuring Atmospheric Changes in the Arctic

Christopher J CoxUniversity of Idaho, Geography

Acknowledgments• Von Walden (UI), Penny Rowe (UI), Matt Shupe (UC, Boulder

• Mike Town (UW), Ed Eloranta (U Wisconsin)

• Funding by National Science Foundation (NSF)

• NOAA SEARCH, CANDAC, ARM, SSEC, IGRA, NSIDC

Outline

• What is climate change?

• The Arctic Climate System

• Instrumentation

• Preliminary research

• Conclusion

What is Climate Change?Scientific Consensus

“Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level” (WGI 3.9, SPM)

•Intergovernmental Panel on Climate Change (IPCC)

Climate change no longer a scientific debate, but a societal issue

What is Climate Change?The Greenhouse Effect

What is Climate Change?The Greenhouse Effect

Global atmospheric concentrations of carbon dioxide, methane, and nitrous oxide (all greenhouse gases) have

increased markedly as a result of human activities since 1750.

IPCC WG1.2 Figure 1

What is Climate Change?The Greenhouse Effect

B1 “Green” Scenario (550 ppm)

A1B “Medium” Scenario (700 ppm)

} Natural Variability

PotentialHuman

Contribution

A1Fl “Aggressive” Scenario (850 ppm)

What is Climate Change?The Greenhouse Effect

So what about Arctic?

Primarily as a result of a strong ice-albedo postive feedback, the Polar Regions are very sensitive to a warming climate.

But, they are also poorly quantified!

Previous Research

Arctic atmosphereSurface Heat Budget of the Arctic (SHEBA)

Intrieri et al (2002) An annual cycle of Arctic surface cloud forcing at SHEBAShupe et al (2005) Arctic mixed-phase cloud properties from surface-based sensors at SHEBA

OtherKey et al (2004) “Cloud distributions over the coastal Arctic Ocean: surface-based and satellite observations”Shupe & Intrieri (2003) “Cloud Radiative Forcing of the Arctic Surface: The Influence of Cloud Properties, Surface Albedo, and Solar Zenith AngleTjernstrom et al (2004) “The Summertime Arctic Atmosphere: meteorological measurements during the Arctic Ocean Experiment 2001”Verlinde et al (2004) “Mixed-Phase Arctic Cloud Experiment (M-PACE)”

Recent Sea Ice MeltDrobot et al (2008) “Evolution of the 2007-2008 Arctic sea ice cover and prospects for a new record in 2008”Kay et al (2008) “The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum”Perovich et al (2008) “Sunlight, water,and ice: Extreme Arctic sea ice melt during the summer of 2007”Schweiger et al (2008) “Did unusually sunny skies helpdrive the record sea ice minimum of 2007?”

Zhang et al (2008) “What drove the dramatic retreat of arctic sea ice during summer 2007?”

The Arctic Climate System

• Cloud properties

– not well known

– climate models

• Downwelling Infrared– Atmospheric properties

– Temperature, Humidity

• Upwelling Infrared– Surface prop (, Ts)

– Satellite validation

Signs of Arctic Climate Change

National Snow and Ice Data Center (NSIDC)

Polar Atmospheric Emitted Radiance Interferometer

Arctic High Spectral Resolution Lidar (AHSRL)Ed Eloranta (SSEC. U. Wisconsin-Madison)

Millimeter Cloud Radar (MMCR)NOAA ERL, Boulder, CO

Microwave Radiometer (MWR) - total column water vaporNOAA ERL, Boulder, CO

Radiosondes from the Eureka Weather Office

http://lidar.ssec.wisc.edu/

Instruments now in the Arctic

Arctic High Spectral Resolution Lidar (AHSRL) LIDAR – Light Detection and Ranging 40 ns pulse width

Wavelength: 523 nm

http://lidar.ssec.wisc.edu/

Instrument SpecsAHSRL

http://arm.gov/

http://lidar.ssec.wisc.edu/

Instrument SpecsMMCR

Millimeter Cloud RadarZenith pointing radarOperates at 35 Ghz

Used to determine cloud boundaries

www.arm.gov

http://arm.gov/

http://lidar.ssec.wisc.edu/

Instrument SpecsMWR

Microwave RadiometerMeasure microwave emission from water (liquid/vapor)

Reports column integrated amounts

www.arm.gov

http://lidar.ssec.wisc.edu/

Instrument SpecsPAERI

Polar Atmos. Emitted Radiance InterferometerSpectral infrared radiance from 3 to 20 m (1 cm-1)

Two detectors: MCT - LW and InSb - SWVery accurate [1% (3) of ambient radiance]

PAERI

PAERI

CO2

H2O

CH4,

N2O

O3

Cloud

PAERI

What can we use PAERI output for?

• Cloud fraction• Trace gas measurements

• Scale radiosondes• Validate satellites

• Longwave cloud radiative forcing• more…

Instrument Sites

Eureka, Nunavut, Canada: Study of Environmental Arctic Change (SEARCH) Arctic Observing Network (AON) at Canadian Network for the Detection of Arctic Change (CANDAC) site

79º59’N, 85º57’W

Barrow, Alaska: Atmospheric Radiation Measurement (ARM) North Slope Alaska (NSA) site

71º18’N, 156º44’W

Longwave Downwelling Radiation and Arctic Sea Ice Melt

• Preliminary experimental evidence for the importance of downwelling longwave radiation to the recent decrease in sea ice concentration over the Arctic Ocean.

• Was shortwave downwelling radiation (SDW) the cause?Kay et al (2008) “The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum”Perovich et al (2008) “Sunlight, water,and ice: Extreme Arctic sea ice melt during the summer of 2007”

• Was it longwave downwelling radiation (LDW)?Schweiger et al (2008) “Did unusually sunny skies helpdrive the record sea ice minimum of 2007?”

Schweiger et al (2008)

Surface Temperature

Tropospheric Temperature

Fractional Cloud Cover

Precipitable Water Vapor

Calculating DLW Flux and LWCRF

AERI measurements made at zenith

Out of band radiance was simulated as a black body

using brightness T from 650-660 cm-1

Assume isotropic radiance (fluxes within ~5%)

Focusing on Eureka data onlyLW CRF = All – Clear

(Ramanathan et al, 1989)

FIR =π I (λ)d(λ)λ1

λ2

∫

Differences in DLW and CRF

• LWCRF depends on many variables• FCC• Optical thickness of clouds• AND Temperature of the near-surface air (in winter)

Cloud Forcing

Inter-annual Variations at Eureka

Eureka Summer Average (JJA)

Year LW-CRF (W m-2) All Sky Flux (Wm-2) FCC (%)

2006 42 275 78

2007 18 263 54

2008 27 268 63

Conclusions• The phenomenon of accelerated climate change is a scientific consensus

• The Arctic is environment is very sensitive to a warming climate and is poorly quantified

• Recent sea ice retreat may be signs of a changing climate system

• Determining the potential causes of recent sea ice decrease in the Arctic is complicated

• Experimental evidence may show that the all-sky flux has influenced sea ice retreat through an increase in the near surface temperature and/or increases in humidity

Sources• Drobot, S; Stroeve, J; Maslanik, J; Emery, W; Fowler, C, and Kay, J. 2008. “Evolution of the 2007-2008 Arctic sea ice cover

and prospects for a new record in 2008”. Geophysical Research Letters. Vol. 25(L19501), 5p.• Intrieri, JM; Shupe, MD; Uttal, T; McCarty, BJ. 2002. “An annual cycle of cloud characteristics observed by radar and lidar at SHEBA” Jounal of Geohpysical Research – Oceans. Vol. 107:C10(8030).• IPCC, 2007, Climate change (2007) Synthesis Report, Summary for Policy Makers, 22p.• Kay, J; L’Ecuyer, T; Gettelman, A; Stephens, G; and O’Dell, C. 2008. “The contribution of cloud and radiation anomalies to

the 2007 Arctic sea ice extent minimum”. Geophysical Research Letters. Vol. 25(L108503), 5p.• Perovich, DK; Richter-Menge, JA; Jones, KF; Light, B. 2008. “Sunlight, water, and ice: Extreme Arctic sea ice melt during the summer of 2007”. Geophysical Research Letters. Vol. 25(L11501), 4p.• Ramanathan, V; Cess, RD; Harrison, EF; Minnis, P; Barkstrom, BR; Ahmad, E; and Hartmann, D. 1989. “Cloud-Radiative

Forcing and Climate: Results from the Earth Radiation Budget Experiment”. Science. Vol. 243(4887), pp 57-63.• Shupe. MD and Intrieri, JM. 2003 . “Cloud Radiative Forcing of the Arctic Surface: The Influence of Cloud Properties, Surface

Albedo, and Solar Zenith Angle”. Journal of Climate. Vol. 17(3), pp.616-628.• Schweiger, AJ; Zhang, J; and Steele, M. 2008. “Did unusually sunny skies help drive the record sea ice minimum of 2007?”

Geophysical Research Letters. Vol. 35(L10503), 6p.• Tjernström, M; Leck, C; Ola, P; Persson, G; Jensen, ML; Oncley, SP; Targino, A. 2004. “The Summertime Arctic Atmosphere: Meteorological Measurements during the Arctic Ocean Experiment 2001”. Bulletin of the American Meteorological Society. Vol. 85(9), pp. 1305-1321.• Town, MS; Walden, VP; and Warren, S. 2005. “Spectral and Broadband Longwave Downwelling Radiative Fluxes, Cloud

Radiative Forcing, and Fractional Cloud Cover over the South Pole”. Journal of Climate. Vol. 18, pp. 4235-4252.• Zhang, J; Lindsay, R; Steele, M; and Scheiger, A. 2008. “What drove the dramatic retreat of arctic sea ice

during summer 2007?” Geophysical Research Letters. Vol. 25(L11505), 5p.