New level 3 SMOS SSS corrected from systematic biases available from CATDS (LOCEAN)

Category : CATDS, L3, Ocean

Jacqueline Boutin from LOCEAN informs you that a

New level 3 SMOS SSS corrected from systematic biases is now available from CATDS/LOCEAN expertise center

Considering that the land contamination leads to systematic biases on retrieved SMOS sea surface salinity, LOCEAN and ACRI-st have developped a method for correcting systematic biases, mostly based on the self consistency of SSS retrieved on various dwell lines. First evaluations of these ‘debiased L3 products’ using ships data show large improvements with respect to previous CEC LOCEAN L3 products.

You can see more on http://www.catds.fr/News/New-level-3-SMOS-SSS-corrected-from-systematic-biases-are-available-from-CATDS-LOCEAN-expertise-center

The new products are available on the CATDS:
ftp eftp.ifremer.fr ; user : c1f135 ; pwd : rXCTqfc0
cd salinity
or ftp://c1f135:rXCTqfc0@eftp.ifremer.fr/salinity/
(or ftp://c1f135:rXCTqfc0@eftp.ifremer.fr/user27285/salinity/
with some web browser)

Enjoy


SMOS 3rd training course is in full swing

Category : Training

The SMOS training course (3rd edition) is currently taking place at the ESA centre of Villafranca (ESAC) in Spain.
18 students from 14 countries together with 4 spectators are currently being « initiated » to the SMOS data in the very nice facilities of ESAC

IMG_2436

Ali presenting image reconstruction (picture by Beatriz)

The course is the third one and takes advantage of the release of the new version (V620) of the SMOS Data while covering both land and ocean science applications (see twitter account)

Next week, the Second post launch SMOS workshop will take place, also at ESAC. Stay tuned!

New data, old features to re-consider…

Category : L2, L3, Ocean

posted by Christophe MAES

blog2smos

Signature of the equatorial upwelling conditions in the Pacific Ocean in terms of SSS (as shown larger than 34.8) in conjunction of SST (black thick line represents the 28°C isotherm, ci=1°C) and of density (blue thick line represents the 22.5 kg/m3 isolign, ci=0.5) as derived from the SMOS satellite mission.

A salient feature of the present-day climate is the equatorial gradient of sea surface temperatures in the Pacific Ocean, characterized by a warm pool in the west (>28°C) and a cold tongue in the east (<20°C). The upwelling conditions caused by the local divergence of currents in the cold tongue also advects salty water upward along the equatorial thermocline. If the climatological evidence broadly depicts such conditions, the space-borne measurements of the SMOS mission reveal for the first time the detailed structure of the SSS signature at the full scale of the Pacific basin (see also the accompanying figure at different time periods). The SSS in the equatorial cold tongue is typically found to be greater than 35.1 within a narrow 2° band of latitude that is positioned slightly south of the equator and that stretches across the eastern Pacific basin up to the Galapagos Islands. On the northern edge of the eastern equatorial Pacific this signature results in a very strong horizontal gradient (larger than 2 units over 100 km) with the fresh waters of the Panama warm pool. By considering a water density criterion (a computation based on SST and SSS fields, both from the satellite mission), it can be shown that the cold tongue is characterized by a strong seasonal cycle with a 3°C amplitude in SST where the warm season of February-March contrasts with the cold season extending from September to November. As the representation of surface salinity in ocean models improves, the present analyses of SSS should prove to be a useful means for investigating the variability of the cold tongue on ENSO and longer interannual time scales.

Reference: The salinity signature of the equatorial Pacific cold tongue as revealed by the satellite SMOS mission, by Christophe Maes (IRD/LPO), Nicolas Reul (IFREMER/LOS), David Behringer (NOAA/NWS/NCEP) and Terence O’Kane (CSIRO); accepted for publication in Geoscience Letters, 2014.

Contact: Christophe.Maes@ird.fr

Potential of SMOS at measuring SSS with a precision better than 0.2 (psu!)

Category : CATDS, L2, Ocean

By J., Boutin, N. Martin, N. Kolodziejczyk and G. Reverdin from LOCEAN/IPSL, Paris

It has been shown by Durand et al. (2013), Reul et al. (2013), Hasson et al. (2014) that SMOS detects large scale interrannual variability of SSS.

The LOCEAN group check this again over 2010-2014. The monthly anomalies of SMOS SSS with respect to a SMOS SSS monthly climatology very well agree with SSS monthly anomalies derived from in situ SSS using the In Situ Analysis System (ISAS) optimal interpolation by F. Gaillard (LPO) and the Coriolis Center.

SMOSAD_ISAS_aSSS

Animation (click to start) : Top: SST anomaly in Niño 3 box from http://www.cpc.ncep.noaa.gov/data/indices/sstoi.indices and corresponding Indian Ocean Dipole (IOD) Index (SST difference between eastern and western equatorial Indian Ocean) from the Australian bureau of Meteorology (BOM). Bottom: SSS monthly anomalies with respect to a monthly climatology (July 2010-June2014): Left)SMOS SSS anomalies; Right)ISAS SSS anomalies

By computing anomalies with respect to 4-year monthly means, SMOS SSS systematic biases are removed. This leads to rms differences between SMOS SSS monthly anomalies and ISAS SSS monthly anomalies the order of 0.2 over large regions, while rms difference of SMOS SSS minus ISAS SSS are on the order of 0.4 over large regions.

image boutin

Figure: Bias (top right) and standard deviation (bottom right) of the differences between SMOS and ISAS monthly SSS (red) and between SMOS and ISAS SSSanomalies (Blue). 6 regions are considered (from left to right): 60°S-60°N; 45°S-45°N; 30°S-30°N; (45°S-5°S, 140°W-95°W); (15°N-30°N,45°W-30°W); (5°N-15°N,110°W-180°W)

Part of this rms difference is due to spatial structures at shorter scale than 300km not resolved by ISAS (Hernandez et al. 2014). Hence this result strongly suggests that SMOS has the potential of measuring SSS at monthly and 100×100km2 scale with a precision better than 0.2 (Hernandez et al. 2014 found 0.15 in the subtropical north Atlantic) provided that systematic biases are removed.

This study has been performed with CATDS CEC-LOCEAN maps built using ESA version 5 reprocessed SSS. Systematic latitudinal biases present in version 5 are expected to decrease in version 6.

Durand, F., G. Alory, R. Dussin, and N. Reul (2013), SMOS reveals the signature of Indian Ocean Dipole events, Ocean Dynamics, 63(11-12), 1203-1212.

Hasson, A., T. Delcroix, J. Boutin, R. Dussin, and J. Ballabrera-Poy (2014), Analyzing the 2010–2011 La Niña signature in the tropical Pacific sea surface salinity using in situ data, SMOS observations, and a numerical simulation, Journal of Geophysical Research: Oceans, 119(6), 3855-3867, doi:10.1002/2013JC009388.

Hernandez, O., J. Boutin, N. Kolodziejczyk, G. Reverdin, N. Martin, F. Gaillard, N. Reul, and J. L. Vergely (2014), SMOS salinity in the subtropical north Atlantic salinity maximum: 1. Comparison with Aquarius and in situ salinity, Journal of Geophysical Research: Oceans, in press.

Reul, N., et al. (2013), Sea Surface Salinity Observations from Space with the SMOS Satellite: A New Means to Monitor the Marine Branch of the Water Cycle, Surv Geophys, 1-42.