ESA Climate Change Initiative Phase-II Sea Surface Temperature (SST) Phase I results and Phase II plans for climate research Nick Rayner CMUG integration meeting, 2-4 th June 2014

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 2 CMUG 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 ClimateSST CCI

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 3 CMUG Integration meeting, Met Office, Exeter The three ESA SST CCI LT version 1.0 products assessed are: o ATSR. SSTs from ATSR instruments in L3U format at 0.05° latitude by 0.05° longitude resolution covering 1991 – (Hereafter, SST CCI ATSR.) o AVHRR. SSTs from AVHRR instruments in L2P format at Global Area Coverage (GAC) resolution covering 1991 – (Hereafter, SST CCI AVHRR.) o 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 – (Hereafter, SST CCI analysis.) These are utilised over the period SST CCI products

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 4 CMUG 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 5 CMUG Integration meeting, Met Office, Exeter Phase II plans: Sea surface temperature user workshop on uncertainties Met 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 6 CMUG Integration meeting, Met Office, Exeter Global, monthly average SST anomaly (relative to average for ) 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 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 7 CMUG Integration meeting, Met Office, Exeter Stability SST CCI 95% confidence interval (mK year -1 ) for 1991 – 1995 DayNightBoth SST CCI AVHRR <trend< <trend<462.3 SST CCI ATSR -13.6<trend< <trend<36.8 SST CCI analysis -1.8<trend<22.1 SST CCI 95% confidence interval (mK year -1 ) for 1995 – 2010 DayNightBoth SST CCI AVHRR < trend < < trend < 2.0 SST CCI ATSR 0.7 < trend < < 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 8 CMUG 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 21 st 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 9 CMUG Integration meeting, Met Office, Exeter Coupled model evaluation Simulated SST Simulated minus SST CCI Simulated minus Daily OI SST CCI minus Daily OI

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 10 CMUG 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 11 CMUG 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, 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 12 CMUG 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 13 CMUG Integration meeting, Met Office, Exeter Improved feature resolution Jun–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 14 CMUG 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 SST fnd 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 15 CMUG 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 16 CMUG 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 OSTIAUpdated OSTIA Drifter o-b0.52(-0.01)0.37(0.00) AATSR o-b0.45(0.04)0.37(0.03) ARGO o-a0.47(0.03)0.43(0.04) Observation-minus-background/analysis RMSE (bias) calculated for March New background covariance errors : Results SST gradients in Gulf Stream in SST CCI analysis

SST CCI Phase I results and Phase II plans for climate research 2 June 2014 Page 17 CMUG Integration meeting, Met Office, Exeter Phase II plans: dedicated climate modelling Malcolm 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 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 18 CMUG 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 19 CMUG 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 20 CMUG Integration meeting, Met Office, Exeter Summary (see also CAR at 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