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SMOS L2 Ocean Salinity
www.argans.co.uk
Level 2 Ocean Salinity
v63x product design evolution
22 April 2015
ARGANS & SMOS L2OS ESL
1
SMOS L2 Ocean Salinity
www.argans.co.uk
When to apply land-sea correction?
2
L2OS TDS (lsc01/2):
•Outlier detection (decision tree): apply OTT & LSC. Sets measurement, snapshot & RFI flags.
•If retrieving A3TEC for OTT computation, do not apply OTT or LSC (A3TEC algorithm retrieves OTT)
•Compute OTT correction per model M1/2/3 (ottTB in AUX_DTBXY: mean forward model OTT TB for all measurements in each snapshot FOV sub-zone, can be compared to modelTB/deltaTB) – not used in retrievals
•If A3TEC for retrievals, apply OTT & LSC (A3TEC does not retrieve OTT), & compute outlier detection again using new TEC.
•For each retrieval (M1/2/3 & Acard), apply OTT & LSC per grid point
SMOS L2 Ocean Salinity
www.argans.co.uk
Design for land-sea correction
3
• 4 x retrievals in v62x: SSS1/2/3 & Acard4 threads gives ~12:1 reprocessing performanceConvergence algorithm ~28% of processing timeMax RAM ~ 6G
• Land-sea LUT (containing ascending & descending LUTs) is ~2.2GCould split into 2, but no performance advantage
• Reading land-sea LUT takes ~ 30 seconds, applying LUT very fast.
• Land-sea LUT is applied at the same time as OTT, before running A3TEC retrieval, measurement selection, & convergence (per forward model).
• Land-sea LUT adds ~0.9G (not scene dependent).
SMOS L2 Ocean Salinity
www.argans.co.uk
Options for land-sea correction
4
A. 4 x retrievals with land-sea correction applied to SSS1/2/3 & Acard (or a selection of these)
(same as May 2011 lsc01/2 TDS)No UDP/DAP format changes requiredNo significant impact on processing performance
B. Retrieve SSS with & without land-sea correction: which model?UDP will contain 2 x SSS & AcardFaster processing (only 3 retrievals): 14:1 (M1) or better
C. 6 x retrievals with & without land-sea correction applied to SSS1/2/3, & AcardUDP will contain 6 x SSS, & AcardProcessing performance degraded to 10:1
Best for users:UDP with 1 SSS selected from several (<4) retrievals, & 1 AcardDAP can contain anything – ie all retrieval resultsAll retrievals with land-sea correction applied (via config switch)Need criteria to select which SSS to write into UDP…
SMOS L2 Ocean Salinity
www.argans.co.uk
SSS1/2/3 are similar due to OTT & land-sea correction
5SSS1
SMOS L2 Ocean Salinity
www.argans.co.uk
SSS1/2/3 are similar due to OTT & land-sea correction
6SSS2
SMOS L2 Ocean Salinity
www.argans.co.uk
SSS1/2/3 are similar due to OTT & land-sea correction
7SSS3
SMOS L2 Ocean Salinity
www.argans.co.uk
Criteria to select a single SSS for UDP
8
Need results from ESL analysis (& JLV T1.3)
Criteria could include:Best (lowest) Dg_quality_SSSxBest Dg_chi2/chi2PNo poor_retrieval flags raisedClassification of geophysical conditions: do some models perform better eg in cold waters or high winds?
Or average of all 3 SSS (if no poor quality flags & Dg_quality < 150)?
SMOS L2 Ocean Salinity
www.argans.co.uk
UDP design
n x grid points:
Grid point data (6)
ID, latitude, longitude, footprint, time, x_swath
Science flags (4 x 22)land, rain, ice, sea state, hi/lo wind/SST/SSS
Geophysical retrievals (10)
SSS1, SSS2, SSS3, Acard& sigmas, WS, SST
TB42.5 (8)
modelled BTs & sigmas at surface & antenna
Product confidence (33)
quality index, chi2, chi2P, nIter for SSS1/2/3/AcardDg_xxx counters (17)
Control flags (4 x 30)ignored, valid, range, sigma, chi2, chi2P, sun/moon/gal glint, maxiter, meas min/low, outliers, marq, rough, foam, ecmwf, poor geophysical/retrieval, rfi
v62x (208 flags & 58 fields) v63x (54 flags & 59 fields)
n x grid points:
Grid point data (6)
ID, latitude, longitude, footprint, time, x_swath
Science flags (1 x 22)land, rain, ice, sea state, hi/lo wind/SST/SSS
Geophysical priors & retrievals (4 x 5)
SSS, WS, SST, TEC, Acard & sigmas
TB42.5 (8)modelled BTs & sigmas at surface & antenna
Product confidence (25)
quality index, chi2, chi2P, nIter for SSS/AcardDg_xxx counters (17)
Control flags (1 x 32)
ignored, valid, range, sigma, chi2, chi2P, sun/moon/gal glint, maxiter, meas min/low, outliers, marq, rough, foam, ecmwf, poor geophysical/retrieval, rfi, model
SMOS L2 Ocean Salinity
www.argans.co.uk
UDP/DAP format changes: decisions & actions
10
• Always apply land-sea correction?
• Single SSS in UDP?
• Run all 3 models in convergence algorithm, select ‘best’ SSS?