ESA Climate Change Initiative Phase-II

Sea Surface Temperature (SST)

www.esa-sst-cci.org

Phase I results and Phase II plans for climate researchNick RaynerCMUG integration meeting, 2-4th June 2014

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 2CMUG Integration meeting, Met Office, Exeter

Optimised impact of ATSRs in SST CDR New Multisensor Matchup System (MMS) supported

techniques to cross-reference AVHRRs to ATSRs● This gives AVHRR density of sampling …● … with improved accuracy, stability and independence from ATSRs

Daily independent “climate-quality” coverage

ATSR Reprocessing for Climate SST CCI

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 3CMUG Integration meeting, Met Office, Exeter

The three ESA SST CCI LT version 1.0 products assessed are:● ATSR. SSTs from ATSR instruments in L3U format at 0.05° latitude by 0.05°

longitude resolution covering 1991 – 2010. (Hereafter, SST CCI ATSR.) ● AVHRR. SSTs from AVHRR instruments in L2P format at Global Area Coverage

(GAC) resolution covering 1991 – 2010. (Hereafter, SST CCI AVHRR.)● Analysis. Satellite-only SST-depth L4 daily analysis created by OSTIA system

from SST CCI ATSR and SST CCI AVHRR products at 0.05° latitude by 0.05° longitude resolution covering 1991 – 2010. (Hereafter, SST CCI analysis.)

These are utilised over the period 1991-2010.

SST CCI products

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 4CMUG Integration meeting, Met Office, Exeter

URD established no commonality of spatio-temporal resolution required by climate users

Therefore, SST CCI provides data at a fundamental resolution (4 km / 0.05 deg; daily) and a tool to create lower-resolution data

Uncertainty estimates should be provided with every SST At L2P / L3U this is estimated as part of the retrieval process

For uncertainty estimates to be available for lower-res outputs of the tool, need to separate components of uncertainty that respond to averaging differently

First time these have been estimated and provided in an EO product (?)

View uncertainty estimates as part of product as much as the SSTs themselves

Uncertainty estimates are therefore validated in their own right

Uncertainty Estimation

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 5CMUG Integration meeting, Met Office, Exeter

Phase II plans: Sea surface temperature user workshop on uncertaintiesMet Office Hadley Centre, Exeter, UK, 18-20th November 2014

The aims of the meeting are to:

Exchange information about uncertainties in sea surface temperature (SST) observations;

Create new expert SST users who, through publication of their work, can inspire others to take uncertainty information into account;

Source requirements from SST users on uncertainty information and other aspects of the Climate Data Records;

Spread best practice through a follow-on meeting report or journal article.

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 6CMUG Integration meeting, Met Office, Exeter

Global, monthly average SST anomaly (relative to average for 1985-2007)

Overall variability is similar except for erroneous variability in the 1990s in the SST CCI AVHRR and ATSR products.

The SST CCI products are more consistent after 1996.

Trend of SST CCI products is at upper end of comparison range

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 7CMUG Integration meeting, Met Office, Exeter

StabilitySST CCI 95% confidence interval (mK year-1) for 1991 – 1995

Day Night Both

SST CCI AVHRR

-137.9<trend<-2.4 105.9<trend<462.3

SST CCI ATSR

-13.6<trend<60.1 -7.4<trend<36.8

SST CCI analysis

-1.8<trend<22.1

SST CCI 95% confidence interval (mK year-1) for 1995 – 2010

Day Night Both

SST CCI AVHRR

-12.3 < trend < -7.4 -2.0 < trend < 2.0

SST CCI ATSR

0.7 < trend < 3.2 -1.4 < trend < 6.4

SST CCI analysis

0.1 < trend < 3.2

GCOS target is 3mK/year

SST difference between SST CCI products and the GTMBA

SST CCI ATSR

SST CCI AVHRR

SST CCI analysis

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 8CMUG Integration meeting, Met Office, Exeter

Phase II option 8: Use of Argo network

Develop and test new ways to assess the stability of the SST CCI products

Assess whether or not Argo network offers satisfactory stability reference data set for the 21st century

Assess SST CCI products for artificial trends and step changes through comparison to moored buoys and the Argo network

May allow assessment of stability globally – currently only possible in the tropical Pacific.

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 9CMUG Integration meeting, Met Office, Exeter

Coupled model evaluation

Simulated SST Simulated minus SST CCI

Simulated minus Daily OISST CCI minus Daily OI

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 10CMUG Integration meeting, Met Office, Exeter

North Indian Ocean

Spurious variability in North Indian Ocean in SST CCI AVHRR product

Thought to be due to CLAVR-X cloud detection passing desert dust

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 11CMUG Integration meeting, Met Office, Exeter

Phase II option 11: passive microwave SST production and impact assessment

Development of microwave SST products from AMSR-E and AMSR-2

Blending with SST retrievals from infrared sensors to create L4 analysis, 2002-2016

May improve retrievals in challenging regions with high aerosol/dust loading or in persistently cloudy regions.

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 12CMUG Integration meeting, Met Office, Exeter

Regional phenomena – Dipole Mode Index

Overall variability is similar in the SST CCI and comparison with some differences.

Peak seen in comparison data sets in 2009/10 missing in SST CCI products

Some peaks to trough variability higher in SST CCI products

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 13CMUG Integration meeting, Met Office, Exeter

Improved feature resolutionJun–Dec 1997

Cold area off Indonesia is much colder in SST CCI products

In situ only data sets have much weaker cold anomaly:

e.g. HadSST3, ERSST, Kaplan, COBE

Similar improvements are seen in the Tropical Atlantic

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 14CMUG Integration meeting, Met Office, Exeter

Exploration of heat transport in ocean models via Tropical instability Waves

Provision of daily mean information in SST CCI analysis is a better natural comparator to the simulated daily data than SSTfnd or the daily “means” provided in the Daily OI.

Courtesy Tim Graham (submitted to Ocean Modelling)

Improved agreement during the El Nino period

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 15CMUG Integration meeting, Met Office, Exeter

Simulation of tropical storm track density

The tropical cyclone tracks may be influenced by the higher SSTs in the SST CCI analysis compared to those in the Reynolds et al Daily OI.

Courtesy Malcolm Roberts (submitted to CLIVAR Exchanges)

tracks shifted slightly southwards, elongated and slightly more frequent

increase in the frequency of tropical cyclone tracks

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 16CMUG Integration meeting, Met Office, Exeter

• Improvements to analysis method (the OSTIA system): background errors and improvement to numerical convergence

• Improved accuracy of SST CCI analysis

• Improved resolution of small-scale ocean features without introducing unrealistic observational noise.

Old OSTIA Updated OSTIA

Drifter o-b 0.52(-0.01) 0.37(0.00)

AATSR o-b 0.45(0.04) 0.37(0.03)

ARGO o-a 0.47(0.03) 0.43(0.04)

Observation-minus-background/analysis RMSE (bias) calculated for March 2012.

New background covariance errors: ResultsSST gradients in Gulf Stream in SST CCI analysis

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 17CMUG Integration meeting, Met Office, Exeter

Phase II plans: dedicated climate modellingMalcolm Roberts, Met Office Hadley Centre

In the third year of the project, we will run simulations using the latest version of the Met Office Hadley Centre model at a spatial resolution of about 25km.

This will be achieved by running two dedicated experiments where the atmosphere is driven by (i) the SST analysis used as standard for such experiments, possibly the Reynolds et al Daily OI and (ii) reprocessing 3 of the SST CCI L4 analysis.

These simulations will be made for about 30 years of the 1981-2016 period, using exactly the same model version, allowing a robust assessment of the impact.

It will be necessary prior to the analysis to choose specific processes or locations to analyse according to our assessment of where the greatest impact is likely to be.

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 18CMUG Integration meeting, Met Office, Exeter

To extend the SST CCI climate data record (CDR) before and after the period of the Along-Track Scanning Radiometers (ATSRs);

To evolve the SST CCI CDR throughout the data period…

To evolve the existing prototype system into an implementation that is :

● sustainable in the long term● able to harness the best scientific SST R&D● able to provide necessary performance:

– a ‘nimble’ improvement cycle for reprocessing– high-performance capacity to store and process relevant data

flows now and in the coming era of Sentinel missions

Phase II: Principal challenges

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 19CMUG Integration meeting, Met Office, Exeter

R&D Passive Microwave Sensors

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 20CMUG Integration meeting, Met Office, Exeter

Summary (see also CAR at http://www.esa-sst-cci.org/?q=webfm_send/104)

SST CCI Phase I products demonstrated to be of use in various climate research applications

Challenges remain, e.g. noise in AVHRR retrievals in Arabian Sea arising from intermittent desert dust episodes; inability to assess stability outside of the tropical Pacific; the need to create a stable record back to 1981

In Phase II, we will:

host a user workshop to discuss needs for and presentation of uncertainty information;

perform 30-year 25km resolution climate model simulations, driven by the SST CCI analysis product to explore the impact of improved resolution on aspects of atmospheric variability;

automate aspects of the climate assessment framework to facilitate the development of a sustainable system;

continue to encourage users of the SST CCI products to provide feedback on their use of the data