Www.argans.co.uk SMOS L2 Ocean Salinity Level 2 Ocean Salinity QWG #4 7-9 March 2011 ARGANS & L2OS ESL

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SMOS L2 Ocean Salinity

Level 2 Ocean Salinity QWG #4

7-9 March 2011

ARGANS & L2OS ESL

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• Level 1 fixed cal reprocessing analysis (presentation by J. Tenerelli)– Drift (impact of TP7 correction)– Sun impact

• LO decimation study (TN/presentation by J. Font)• Radiometric accuracy & sun flags (presentation by X. Yin)• OTT drift and quality analysis• OTT sensitivity study:

– impact of galaxy signal, num. snapshots, time window (BEC presentation @ PM#20)

• Outliers detection to identify RFI• Upgrading roughness models

– Rough 1: foam effect added, change in surface spectrum– Rough 2: going to an empirical roughness correction– Rough 3: improving LUT, going to fully empirical model

Scientific status

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L2OS status

27 December 2010

10 January 2011

8 February 2011

L2OS 0316 enters its 9th month of processing in DPGS...

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• 317 history– delivered 22 November 2010; FAT passed 7 December 2010– January installation delayed (L1OP not available)– new roughness model 3 LUT & OTTs for January calibration delivered early February– management meeting 9 February approves installation 317– 18-25 February IDEAS reject 317 due to AUX_BULL_B validity period issues (40+ emails)– go-ahead for 317 to be installed in DPGS March...

• Issues:– L2OS ESL lose 2+ months pre-reprocessing DPGS data analysis– L2OS processor development/testing for summer delivery still using L1OP 34x

• no L1c 35x with correct RFI flags yet!

• 500 history?

L2OS status

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New roughness 3 LUT

SM_TEST_AUX_RGHNS3_20050101T000000_20500101T000000_001_012_8(19/11/2010)

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New roughness 3 LUT

SM_TEST_AUX_RGHNS3_20050101T000000_20500101T000000_001_013_8(21/01/2011)

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• Outlier test:– abs((Tbmeas - Tbmodel) - correction) > nsig . sigmaTb

• ATBD:– correction = median (Tbmeas - Tbmodel)

• DPM & 0317:– correction = median (Tbmeas) – median(Tbmodel)

Outlier detection

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Outlier detection

TN analysis prepared by Claire Henocq, Jean-Luc Vergely & Jacqueline Boutin

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Outlier detection

No longer considered

outliers

New outliers

TN analysis prepared by Claire Henocq, Jean-Luc Vergely & Jacqueline Boutin

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Outlier detection

• Number of outliers plotted against longitude (0317), latitude +- 1 degree

• total outliers 8477, 1570 grid points

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Outlier detection

• Number of outliers plotted against longitude (0318), latitude +- 1 degree

• total outliers 7802, 1570 grid points

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Outlier detection: SSS1

0317 0318 delta (317-318)SM_OPER_MIR_SCSF1C_20100802T153816_20100802T163215_344_001_1

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Outlier detection: Dg_num_outliers

0317 0318 delta (317-318)SM_OPER_MIR_SCSF1C_20100802T153816_20100802T163215_344_001_1

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L1 & L2 RFI flags

• L2 fm_l1c_rfi set if any of L1c flags set:– fml1c_rfi_mitigation– fml1c_rfi_strong– fml1c_rfi_point

• L2OS 0317 sets fm_valid = false if fm_l1c_rfi set

• Some orbits may have L1 RFI flags set over a wide area, egSM_TEST_MIR_SCSF1C_20100315T080748_20100315T090119_350_001_0

• So L2OS 0317 will find too few measurements for many grid points, leading to missing salinity retrievals

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L1 & L2 RFI flags

0317 0318 few outliers?SM_TEST_MIR_SCSF1C_20100315T080748_20100315T090119_350_001_0

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Rain Rate

ECMWF rain rate is metres/hour (103 litres per m2 per hour), not mm/hrMax values are typically 0.02-0.03 in storms.AUX_CNFOSD/F sets Tg_max_rainfall = 2, so Fg_sc_rain is never set

ECMWF Rain_Rate

Fg_sc_rain (Tg_max_rainfall = 0.002)

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• Presentation by J. Tenerelli: land contamination

• Radiometric accuracy & sun flags (presentation by X. Yin)

• RFI detection (presentation by P. Spurgeon)

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Validation of current DPGS L2OS• Using L3 operationally generated by CP34

– SMOS SSS (10 days L3 product) – WOA2005 SSS (climatology for February)

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– SMOS SSS (10 days L3 product) – Argo at -7.5 m (same period)

Bias 0.26 psuSTD 0.81 psu

Still a lot to improve!

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Towards reprocessing• L2OS upcoming improvements for (May/June) delivery (v500)

– RFI detection/mitigation• Fg_ctrl_suspect_RFI (no impact on schema), Dg_num_RFI_outliers (UDP schema change)• switch RFI detection on/off, add threshold(s) to AUX_CNFOSD/F

– roughness model & configuration tuning• ICM empirical model without flat sea - analysis and algorithm design: CRR impact assessment N/A

– fixed PRs:• outlier detection ATBD/DPM mis-match – detected 1 February• mis-use of L1 RFI flags – detected 27 January• wrong ECMWF rain rate units & Tg_max_rainfall/Fg_sc_rain – detected 4 February• BULL_B validity issues – detected 18 February

• On-going studies– errors in ECMWF WS (compared to SSMI) lead to bias in SSS – work continuing– investigate sun/galactic glint models (mismatch with SMOS data)

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ECMWF/SSMI WS: example of difference

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ECMWF/SSMI WS: Average SSSsmos-SSSargo in classes of 1m/s of WSecmwf-WSssmi

WSecmwf-WSssmi (m/s)

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Time series & site statisticssite monitoring: S. Pacific

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Site monitoring: S. Pacific (ascending)

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Site monitoring: S. Pacific (descending)

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Site monitoring: S. Pacific SSS1/2 correlation

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SMOS, ARGO (August 2010) & CLIMATOLOGICAL SSSColocation +/- 5 days, +/-50km, center swath +/-300km, Ascending orbits

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SMOS Model 1 - ARGO SSS (3-31 August 2010; asc orbits) versus wind speed (center of orbit)

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OTT/drift analysis• Objective

– determine OTT drift & required update frequency

• Analyse DPGS L2OS 316 salinity drift in stable South Pacific zone (0-30S)– retrieved salinity with sigma_SSS error– SSS anomaly (retrieved – climatology)

• Generate new OTT with 0317 for 0, +1, +2, +4, +7, +13, +28, +43 days– 02/08/2010, 03/08/2010, 04/08/2010, 06/08/2010, 09/08/2010, 15/08/2010,

30/08/2010, 14/09/2010

• Compare DPGS L2OS 0316 SSS drift with new OTT drift

• Reprocess reference orbit 02/08/2010 with 0317 & new OTT– plot SSS & anomaly drift

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DPGS 0316 drift, Aug-Dec 2010

Selected South Pacific orbits, 0-30S, xswath ±300km, unfiltered, with sigma_SSS

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DPGS 0316 43 day drift

Selected South Pacific orbits, SSS – climatology, 0-30S, xswath ±300km, unfiltered

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OTT drift

OTT1 delta for selected South Pacific orbits 0-30S, 03/08/2010 to 29/11/2010

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Correlation between OTT & DPGS drift

OTT delta versus mean SSS for selected South Pacific orbits 0-30S

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Reprocessing ref orbit with new OTT

02082010 orbit reprocessed 0317 with OTT from later dates

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OTT/drift analysis discussion• Purpose of OTT:

– correct L1c TBs so L2OS can retrieve good quality salinity – secondary role: diagnostic for L1c quality

• Issues– Wait for L1OP 350 & 317 in DPGS to analyse OTT correction?– Wait for L1PP 500 & L2OS 500 June 2011 & analyse drift/OTT impact?– Perform analysis on fixed cal reprocessed commissioning data?

• Analysis strategies– Routine generation of OTT drift statistics?– UDP SSS anomalies or other metrics (eg time-series statistics, collocation match-ups)– Other?

• OTT strategies– One per day/week/month etc (eg mid-week – good for commissioning data)

• from a single orbit• average of several orbits – eg one ascending & one descending• abrupt transition between OTTs or smoothed – running average?

– One size fits all – single OTT for entire reprocessing?

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Algorithm validation• Once new L1 500 and L2OS 500 are implemented in DPGS, we will check:

– Effectiveness of OTT strategy– Ascending/descending differences– Land contamination– RFI properly removed– Impact of sun and galactic signals– Performance of new roughness models. Comparison of SMOS to Argo and climatology

• Timetable?

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Decisions proposed to QWG #4

• Increasing LO calibration frequency• RFI outlier detection at L2OS • Removing sun correction at L1• Extend L1 SUN_POINT flag to a circle around sun• Flagging suspenders at L1

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Remembering SSS requirements

• R-4.6.2-004 The accuracy of the ocean salinity data products with a 50 km spatial resolution shall be <= 1.2 PSU.Note: This OS Level-2 accuracy requirement corresponds to :· snapshot images (100) of one pixel taken during one single pass,· usage of the narrow swath,· full spatial coverage,· ocean temperature of 277 K

• G-4.7.2-005 The accuracy of the ocean salinity maps outside coastal areas, after averaging over 200 km x 200 km x 10 days space-time domain, shall be <= 0.1 PSU, after corrections by using vicarious calibration, namely by periodical imaging of one or more well-known reference sources.

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On statistics

• During 10 minutes 500 SMOS snapshots are acquired• Calibrating LO every 10 min means loosing 5 snapshots, then the error in

building an L3 map by averaging L2 products (wrt no calibration) increases by sqrt (500)/sqrt(495) = 1.005

• Calibrating every 2 min, 25 snapshots are lost, the L3 error increases by sqrt(500)/sqrt(475) = 1.026

• Going back to one orbit, the increase of usable snapshots @10 min compared to @2 min implies an error reduction of sqrt(495)/ sqrt(475) = 1.02

• This 2% reduction on the required SSS error means 0.02 psu• We showed that calibrating @2 min instead of @10 min implies an error

reduction by 0.2 psu (clean Pacific), 0.5 psu in global average

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AOB

• NIR 2 week calibration• impact on salinity TBD• ascending/descending?

• Monitoring products

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Solar flare?

SM_OPER_MIR_OSDAP2_20110215T015901_20110215T025302_316_002_1

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L1c software error flag

20110302T062507 – 20110302T071906

Documents

Www.argans.co.uk SMOS L2 Ocean Salinity Level 2 Ocean Salinity QWG #4 7-9 March 2011 ARGANS & L2OS ESL