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Phase I results and Phase II plans for climate research. Nick Rayner CMUG integration meeting, 2-4 th June 2014. 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 …
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CMUG integration meeting, 2-4th June 2014
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
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
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 rightUncertainty Estimation
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.
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 difference between SST CCI products and the GTMBA
SST CCI ATSR
SST CCI AVHRR
GCOS target is 3mK/year
SST CCI analysis
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.
Simulated minus SST CCI
Simulated minus Daily OI
SST CCI minus Daily OI
Spurious variability in North Indian Ocean in SST CCI AVHRR product
Thought to be due to CLAVR-X cloud detection passing desert dust
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.
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
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
Exploration of heat transport in ocean models via Tropical instability WavesProvision 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
Simulation of tropical storm track densityThe 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)
increase in the frequency of tropical cyclone tracks
tracks shifted slightly southwards, elongated and slightly more frequent
SST gradients in Gulf Stream in SST CCI analysis
Observation-minus-background/analysis RMSE (bias) calculated for March 2012.
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.
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 missionsPhase II: Principal challenges
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