SMOS L2 Ocean Salinity L2OS RFI study 9 May 2011 ARGANS & L2OS ESL

SMOS L2 Ocean Salinity 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 Fm_L2_rfi = 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

SMOS L2 Ocean Salinity >200 km from land Fg_ctrl_suspect_rfi set if Fm_L2_RFI > 50% L2OS RFI detection (early version of algorithm)

SMOS L2 Ocean Salinity >40 km from land Fm_outlier never set because algorithm skipped outlier test if risk of RFI detected L2OS RFI detection (early version of algorithm)

SMOS L2 Ocean Salinity no RFI detectionRFI detection Fm_L2_RFI higher % than Fm_outlier (ie more sensitive) L2OS RFI detection (early version of algorithm)

SMOS L2 Ocean Salinity no RFI detection RFI detectiondelta Problem: RFI detection works well, but impacts non-RFI retrievals, because measurements discarded if Fm_L2_RFI set even if < 50% L2OS RFI detection (early version of algorithm)

SMOS L2 Ocean Salinity Dg_RFI_L2 = count(Fm_L2_rfi) if (Dg_RFI_L2 / Dg_num_meas_L1c) > Tg_num_RFI_max (50%) then Fg_ctrl_suspect_rfi = TRUE if Fg_ctrl_suspect_rfi then if Fm_L2_rfi then Fm_valid = false else /* use ‘normal’ non-RFI outlier test */ if Fm_outlier then Fm_valid = false Outliers & RFI – extended algorithm

SMOS L2 Ocean Salinity Fg_ctrl_suspect_rfi set if Fm_L2_RFI > 50% Fm_outlier also set, even if risk of RFI detected Fm_L2_RFI higher % than Fm_outlier (ie more sensitive) L2OS RFI detection (current algorithm)

SMOS L2 Ocean Salinity no RFI detection RFI detectiondelta (= RFI – no RFI) Some additional retrievals in Arctic (> 200km from coast) L2OS RFI detection (current algorithm)

SMOS L2 Ocean Salinity L2OS RFI detection (current algorithm) no RFI detection RFI detectiondelta Additional retrievals in North Pacific & Arctic

SMOS L2 Ocean Salinity L2OS RFI detection (current algorithm) > 40km from coast > 200km from coast False RFI detection near Antarctic ice

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_ T185354_ T194756_317_001_1 (unfiltered)

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_ T185354_ T194756_317_001_1 (filtered: 44329/82665)

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v500 SM_TEST_MIR_OSDAP2_ T185354_ T194756_500_001_8 (filtered: 48522/82212) L2 RFI outlier test >40km

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_ T051050_ T060452_317_001_1 (unfiltered)

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_ T051050_ T060452_317_001_1 (filtered: 17957/62361)

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v500 SM_TEST_MIR_OSDAP2_ T051050_ T060452_500_001_8 (filtered: 21683/61963) L2 RFI outlier test >40km

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_ T085851_ T095250_317_001_1 (unfiltered)

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v500 SM_TEST_MIR_OSDAP2_ T085851_ T095250_500_001_8 Fg_ctrl_suspect_RFI

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_ T085851_ T095250_317_001_1 (filtered: 17899/53953)

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v500 SM_TEST_MIR_OSDAP2_ T085851_ T095250_500_001_8 (filtered: 21506/53520) L2 RFI outlier test >40km

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v no RFI detection 500 with RFI detection SM_OPER_MIR_SCSF1C_ T055704_ T065103_346_001_1

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v no RFI detection 500 with RFI detection SM_OPER_MIR_OSDAP2_ T141055_ T150454_317_001_1

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v no RFI detection 500 with RFI detection SM_OPER_MIR_OSDAP2_ T155057_ T164459_317_001_1

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v no RFI detection 500 with RFI detection SM_OPER_MIR_OSDAP2_ T164100_ T173501_317_001_1

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v no RFI detection 500 with RFI detection SM_OPER_MIR_SCSF1C_ T041028_ T050427_346_001_1

SMOS L2 Ocean Salinity L2OS RFI detection comparing 0317 & v no RFI detection 500 with RFI detection SM_OPER_MIR_OSDAP2_ T200742_ T210141_317_001_1

SMOS L2 Ocean Salinity unfiltered filtered Fm_L2_RFI Fg_ctrl_suspect_rfi L2OS RFI detection comparing 0317 & v no RFI detection 500 with RFI detection SM_OPER_MIR_OSDAP2_ T123721_ T133122_317_001_1

SMOS L2 Ocean Salinity Outliers & RFI Conclusions – new L2 RFI algorithm detects RFI – once detected, RFI measurement selection enables &/or improves retrieved salinity – L1 coast contamination causes false RFI positives – RFI thresholds need tuning with new L1 – L2OS configuration can turn RFI detection/mitigation off if required

SMOS L2 Ocean Salinity Decision: RFI distance-to-coast >40km>200km SM_TEST_MIR_OSDAP2_ T005649_ T015043_318_001_8

SMOS L2 Ocean Salinity Decision: RFI distance-to-coast >40km>200km Set coast limit >40km & find good values for RFI_std, RFI_nsig &Tg_num_RFI_max with new L1PP