the cdr from sst cci · sst cci phase-ii esa climate change initiative phase-ii sea surface...
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SST CCI Phase-II
ESA Climate Change Initiative Phase-II
Sea Surface Temperature (SST)
www.esa-sst-cci.org
The CDR from SST CCI Chris Merchant University of Reading
SST CCI Phase-II
R&D Passive Microwave Sensors
35 year uncertainty-quantified SST CDR Integrated, consistent L2, L3 & L4
SST CCI Phase-II
New EO science in SST CCI Phase 2 § Known techniques cannot deliver SST CDR
requirements § New EO science required to
• Harmonise and stabilise AVHRRs/ATSR1 pre-1996 – Mutual bias correction across constellation – Instrument calibration modelling (essential work at L1b)
• Link AATSR to SLSTR via AVHRR-A/IASI • Achieve IR SST targets for noise and bias
– Smooth-atmosphere retrieval to reduce noise – Retrieval and cloud detection in presence of stratospheric aerosol
§ Fundamental work on new MW subskin-SST • in context of IR-dominated CDR
SST CCI Phase-II
Passive Microwave SST § Can PMW SST be used to
enhance the SST CDR? • Enhanced frequency of
observation (at lower resolution) in cloudy areas
• Could damage observational stability of CDR relative to IR-only
§ Optimal estimation for AMSR-2 SST developed
• Information content analysis completed, to prioritise channels
• Significant BT-related and wind-stress related biases
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6.9V Brightness Temperature / K
Est
imat
ed O
bs –
Sim
Bia
s / K
SST CCI Phase-II
Initial PMW SST validation results
21 July 2015 GHRSST XVI Page 5
JAXA RSS CCI Matching Good Buoys 305 161 305 161 305 161 Mean Error / K 0.03 -0.04 -0.14 Robust SD / K 0.40 0.38 0.38
SS
T AM
SR –
SS
T in
situ
/ K
NWP wind speed / m/s
Wind-stress dependence of emissivity around 7 GHz is not well understood
SST CCI Phase-II
Less noisy IR SST § For climate record, priority is to
• minimise biases • maximise sensitivity to true SST
(minimise prior influence)
§ Users also like data that isn’t noisy
• but obvious low-noise retrieval increase bias and prior influence
§ Experimental reprocessing introduced “smooth-atmosphere” retrievals
• the SST fields are not merely smoothed, even if it looks like it
• bias and sensitivity are unchanged
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Low bias, normal noise
Low bias, low noise
SST CCI Phase-II
Stratospheric aerosol events
7
0 0.3 Infra-red optical depth, Pinatubo aerosol
Causes bias in IR SST Good solution exists for ATSR: “aerosol robust” retrieval coeffs
El Chichon (1982) Pinatubo (1991)
SST CCI Phase-II
El Chichon and AVHRRs § Tougher to get a good solution for
AVHRRs • Single view => good knowledge
of spectral impact more crucial • Fundamentally not enough
information in 2 or 3 channels => prior IR AOD
§ Derived using HIRS data a prior IR AOD for El Chichon event
§ Will use this in extension to the optimal estimation scheme presently used
§ Crucial step in extending CDR back to 1981
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FromMerchantetal.,2013communitypaperandroadmap:h"p://www.geosci-instrum-method-data-syst.net/2/305/2013/gi-2-305-2013.html
H2020 project EUSTACE Aim: to understand, parameterise and exploit relationships between satellite (skin) and meteorological air temperature, for global historical analysis
• SST CCI data will be exploited for air temperature analysis
• Key benefit: uncertainty information
EUSTACEhasreceivedfundingfromtheEuropeanUnionHorizon2020Research
andInnovaJonprogramme,underGrantAgreementnumber640171
HadISST2.2 switch to SST CCI • Key benefit of SST CCI: improved AVHRR products • HadISST1 paper ~3000 citations
HadISST.2.1.0.0 ERSSTv3b Kaplan COBE HadISST1
SST CCI Phase-II
Conclusions
§ Building an integrated “operations-ready” system (presented on Day 1)
§ Many innovations to improve the scientific quality of the CDR in progress, and to deal with challenges of early sensors
§ Key to wider user adoption and application will be combination of • reputation -- trust in the quality • 1981 to recent • ongoing extension of CDR in time
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