Www.argans.co.uk SMOS L2 Ocean Salinity L2OS QWG #4: RFI 7-9 March 2011 ARGANS & L2OS ESL.
14
www.argans.co SMOS L2 Ocean Salinity L2OS QWG #4: RFI 7-9 March 2011 ARGANS & L2OS ESL
-
Upload
maggie-hescock -
Category
Documents
-
view
219 -
download
3
Transcript of Www.argans.co.uk SMOS L2 Ocean Salinity L2OS QWG #4: RFI 7-9 March 2011 ARGANS & L2OS ESL.
www.argans.co.uk
SMOS L2 Ocean Salinity
L2OS QWG #4: RFI
7-9 March 2011
ARGANS & L2OS ESL
www.argans.co.uk
SMOS L2 Ocean Salinity
DEW line RFI prevents successful salinity retrieval North Pacific & Atlantic
RFI over the ocean
www.argans.co.uk
SMOS L2 Ocean Salinity
SM_TEST_MIR_OSDAP2_20110209T064251_20110209T073653_317_001_8
Transect at 45N +-1Dg_num_outliers
Outliers & RFI
www.argans.co.uk
SMOS L2 Ocean Salinity
From CH/JLV/JB TN: typical N. Atlantic RFI pattern in salinity (left), typical oscillations in TBs (right)
Outliers & RFI
www.argans.co.uk
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
wherecorrection = median (Tbmeas - Tbmodel)σTB = √ (σTB_radiometric_noise2 + σTBmodel2 )
Outliers & RFIOutlier 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 v3.17 With 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
www.argans.co.uk
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
wherestd_theory = √ ((TB_radiometric_noise2 + TBmodel2 ) / nMeas)factor of 1.2 is 99% confidence with 100 measurements (1 + 0.18)nsig is reduced from 5 (non-RFI outlier detection threshold) to 3
Outliers & RFI
www.argans.co.uk
SMOS L2 Ocean Salinity
0318 new RFI outlier detection algorithm disabledSM_OPER_MIR_SCSF1C_20110209T064251_20110209T073653_346_001_1
Outliers & RFI
www.argans.co.uk
SMOS L2 Ocean Salinity
Outliers & RFI
0318 new RFI outlier detection algorithm enabledSM_OPER_MIR_SCSF1C_20110209T064251_20110209T073653_346_001_1
www.argans.co.uk
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?
www.argans.co.uk
SMOS L2 Ocean Salinity
Outliers & RFI
RFI outlier detection algorithm disabled (left) enabled (right)SM_OPER_MIR_SCSF1C_20100802T153816_20100802T163215_344_001_1
www.argans.co.uk
SMOS L2 Ocean Salinity
Outliers & RFI
RFI outlier detection algorithm disabled (left) enabled (right)SM_OPER_MIR_SCSF1C_20100802T153816_20100802T163215_344_001_1
www.argans.co.uk
SMOS L2 Ocean Salinity
Outliers & RFI – L1PP 350
0318 new RFI outlier detection algorithm enabledSM_TEST_MIR_SCSF1C_20100315T080748_20100315T090119_350_001_0
www.argans.co.uk
SMOS L2 Ocean Salinity
Outliers & RFI – L1PP 350
Any correlation between L1 & L2 RFI flagging?
www.argans.co.uk
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
