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

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Presentation on theme: "Www.argans.co.uk SMOS L2 Ocean Salinity L2OS QWG #4: RFI 7-9 March 2011 ARGANS & L2OS ESL."— Presentation transcript:

1 SMOS L2 Ocean Salinity L2OS QWG #4: RFI 7-9 March 2011 ARGANS & L2OS ESL

2 SMOS L2 Ocean Salinity DEW line RFI prevents successful salinity retrieval North Pacific & Atlantic RFI over the ocean

3 SMOS L2 Ocean Salinity SM_TEST_MIR_OSDAP2_ T064251_ T073653_317_001_8 Transect at 45N +-1 Dg_num_outliers Outliers & RFI

4 SMOS L2 Ocean Salinity From CH/JLV/JB TN: typical N. Atlantic RFI pattern in salinity (left), typical oscillations in TBs (right) Outliers & RFI

5 SMOS L2 Ocean Salinity 0317 outlier detection algorithm for pol = 0 to 3 /* Stokes 1..4 */ for each measurement if abs((Tbsmos[pol] – Tbmodel[pol]) – correction[pol]) > 5 * σTB then outlier[pol, meas] = TRUE where correction = median (Tbmeas - Tbmodel) σTB = √ (σTB_radiometric_noise 2 + σTBmodel 2 ) Outliers & RFI Outlier detection in L2OSPP and its usefulness in RFI detection and correction – HENOCQ et al, SMOS L2OS technical note, 28/02/11 Some Tests close to Greenland New algorithm more consistent and effective (below outliers=filled points) A B A B With L2OSPP v3.17With new algorithm Refinements: - If no RFI, 3 sigma sorting may discard good measurements :  Add a first step at gridpoint level for identifying the risk of outliers (see TN) Future work: -use « up and down evolution » of (Btmeas– BTmodel) over a dwell to detect RFI

6 SMOS L2 Ocean Salinity 0318 new 2 step RFI outlier detection algorithm based on reducing outlier threshold if high probability of RFI detected for pol = 0 to 3 /* Stokes 1..4 */ if std(TBmodel[pol] - TBsmos[pol]) > 1.2 * std_theory then rfi_outlier_risk[pol] = TRUE if rfi_outlier_risk[pol] then for each measurement if abs(TBmodel[pol] - TBsmos[pol]) > 3 * rad_noise then rfi_outlier[pol, meas] = TRUE where std_theory = √ ((TB_radiometric_noise 2 + TBmodel 2 ) / nMeas) factor of 1.2 is 99% confidence with 100 measurements ( ) nsig is reduced from 5 (non-RFI outlier detection threshold) to 3 Outliers & RFI

7 SMOS L2 Ocean Salinity 0318 new RFI outlier detection algorithm disabled SM_OPER_MIR_SCSF1C_ T064251_ T073653_346_001_1 Outliers & RFI

8 SMOS L2 Ocean Salinity Outliers & RFI 0318 new RFI outlier detection algorithm enabled SM_OPER_MIR_SCSF1C_ T064251_ T073653_346_001_1

9 SMOS L2 Ocean Salinity Outliers & RFI Fg_ctrl_suspect_RFI = RFI outliers > 50%delta SSS1 (RFI off – on) Danger of false positives?Impact on non-RFI retrieval?

10 SMOS L2 Ocean Salinity Outliers & RFI RFI outlier detection algorithm disabled (left)enabled (right) SM_OPER_MIR_SCSF1C_ T153816_ T163215_344_001_1

11 SMOS L2 Ocean Salinity Outliers & RFI RFI outlier detection algorithm disabled (left)enabled (right) SM_OPER_MIR_SCSF1C_ T153816_ T163215_344_001_1

12 SMOS L2 Ocean Salinity Outliers & RFI – L1PP new RFI outlier detection algorithm enabled SM_TEST_MIR_SCSF1C_ T080748_ T090119_350_001_0

13 SMOS L2 Ocean Salinity Outliers & RFI – L1PP 350 Any correlation between L1 & L2 RFI flagging?

14 SMOS L2 Ocean Salinity Other possible RFI detection approaches Detecting RFI induced oscillations in dwell line TBs (eg using fft) – see TN from Claire, Jacqueline & Jean-Luc (oscillations seem higher in VV?): Using L1c RFI flags? Using AUX_RFILST? CATDS use one month data in 5 degree bins per grid point... Outliers & RFI


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