OS-ESL meeting, Barcelona, February nd, 2011 OTT sensitivity study and Sun correction impact J. Gourrion and the SMOS-BEC team SMOS-BEC, ICM/CSIC

OS-ESL meeting, Barcelona, February nd, 2011 OTT sensitivity  DPGS OTT  Impact on OTT quality of different factors: 1.Galactic signals 2.Number of snapshots used 3.Apparent drift (or temporal integration window width)  Experiments designed to remove inter-dependence  OTT quality criterion: stability, level of dependence on the subset of data

OS-ESL meeting, Barcelona, February nd, 2011 OTT sensitivity  Force independence of factor 2 (constant number of snapshots N) and 3 (use a 12-days period)  Galactic potential contamination detection: threshold on the incident field (3.5 to 8 K)  For each threshold value, N snapshots are randomly selected, and an OTT computed  Using the lowest threshold value as reference, we compute the OTT rms increase due to increasing galactic contamination Impact of galactic contamination

OS-ESL meeting, Barcelona, February nd, 2011  Force independence of factor 1 (strict galactic filter) and 3 (use a 12-days period)  For three different periods, the reference situation is given by the overall number of available snapshots after filtering.  the number of snapshots is progressively reduced, snapshots are randomly selected and corresponding OTTs are computed  OTT rms increase is computed as a function of snapshot number reduction factor and averaged over the 3 datasets (consistency checked) OTT sensitivity Impact of number of snapshots

OS-ESL meeting, Barcelona, February nd, 2011 OTT sensitivity Impact of number of snapshots

OS-ESL meeting, Barcelona, February nd, 2011 OTT sensitivity Impact of number of snapshots

OS-ESL meeting, Barcelona, February nd, 2011  Force independence of factor 1 (strict galactic filter) and 2 (constant number of snapshots N)  The temporal window width is increased from 6 days to 48 days  In each case, N snapshots are randomly selected, and an OTT computed  Using the shortest temporal window as reference, we compute the OTT rms increase due to increasing data inconsistency OTT sensitivity Impact of apparent drift

OS-ESL meeting, Barcelona, February nd, 2011  As expected, the number of snapshots used to compute the OTT should be kept as high as possible, the upper limit being set by other constraints  Galaxy presence in the snapshots used to compute the OTT may induce large errors in the characterization of systematic instrument/reconstruction biases (up to 0.4 K rms at X- and Y-pol)  Apparent instrumental drift can induce significant errors. If not canceled, numbers provided should help defining the OTT recomputation period. OTT sensitivity Summary

OS-ESL meeting, Barcelona, February nd, 2011 Direct sun correction impact Using DPGS file : SM_OPER_MIR_SC_F1B_ T131914_ T141314_340_001_0

OS-ESL meeting, Barcelona, February nd, 2011 Direct sun correction impact Using DPGS file : SM_OPER_MIR_SC_F1B_ T131914_ T141314_340_001_0

OS-ESL meeting, Barcelona, February nd, 2011 Direct sun correction impact Using DPGS file : SM_OPER_MIR_SC_F1B_ T131914_ T141314_340_001_0 * K shift * no impact on latitudinal variations

OS-ESL meeting, Barcelona, February nd, 2011 Direct sun correction impact Using DPGS file : SM_OPER_MIR_SC_F1B_ T031502_ T040900_340_001_0

OS-ESL meeting, Barcelona, February nd, 2011 Direct sun correction impact Using DPGS file : SM_OPER_MIR_SC_F1B_ T031502_ T040900_340_001_0

OS-ESL meeting, Barcelona, February nd, 2011 Direct sun correction impact Using DPGS file : SM_OPER_MIR_SC_F1B_ T031502_ T040900_340_001_0 1K impact on latitudinal variations

OS-ESL meeting, Barcelona, February nd, 2011 Data processing  31 days week of Full-pol data from Augus  Level 1 Operational Processor version  Land contamination detected at Level 1B: much wider FOV than at L1C  Only pure Ocean scenes are kept (less than 0.25% of land pixels)  RFI detection in the Alias-Free FOV: threshold on the allowed maximum departure from model (20 K)  Reconstruction bias pattern estimated from the 6-days dataset subsampled to homogenize the geophysical conditions histograms (wind speed and SST) over the FOV.

OS-ESL meeting, Barcelona, February nd, 2011 Summary  Variability of the distribution of observed geophysical conditions inside the FOV, when computing the OTT, may introduce inconsistencies in the modified brightness temperatures  Adequate snapshot selection procedure enables to reduce consequent biases in the retrieved salinities. The procedure requires much more data than one half-orbit.  The residual SSS anomalies are highly reduced when using a roughness-improved forward model (IQR divided by 2, Y-pol)  In terms of salinity, X-pol is much noisier than Y-pol.  To further reduce the SSS errors:  work on the roughness description and more generally on the forward model  improve the inversion method from the present linear approach