IGARSS 2010, Honolulu, July 25-30, 2010 1
Overview of SMOS level 2 ocean salinity processing and first results
J. Font, J. Boutin, N. Reul, P. Spurgeon, J. Ballabrera, A. Chuprin, C. Gabarró, J. Gourrion, C. Hénocq, S. Lavender, N. Martin, J. Martínez, M. McCulloch, I. Meirold-Mautner, F. Petitcolin, M. Portabella, R. Sabia, M. Talone, J. Tenerelli, A. Turiel, J.L. Vergely, P. Waldteufel, X. Yin, S. Zine,
S. Delwart (The SMOS L2 OS Team)
ICM-CSIC/SMOS-BEC Barcelona, LOCEAN Paris, IFREMER Brest,ARGANS Plymouth, ACRI-ST Sophie-Antipolis, ESA-ESTEC Noordwijk
IGARSS 2010, Honolulu, July 25-30, 2010 2
SMOS SSS mission requirements
• The multiangular measurements of any point on the Earth’s surface provided by the SMOS interferometric radiometer MIRAS at each satellite overpass are aimed at: – Determining sea surface salinity with an accuracy of the
order of 0.1 practical salinity units, 100 – 200 km spatial resolution and 10 – 30 days temporal resolution
Useful for large scale
oceanographic and climate
studies
(© P. Carril for ESA)
IGARSS 2010, Honolulu, July 25-30, 2010 3
Sensitivity of Tb to SSS is small
especially at low temperatures
Retrieving salinity with SMOS is a challenge that requires very good
performance of the instrument and a very demanding data processing:
new models and algorithms being implemented and now improved
Polarisation and viewing geometry
provide a higher range of Tb values
SSS and Tb values
IGARSS 2010, Honolulu, July 25-30, 2010 4
SMOS Sea Surface Salinity retrieval
• Retrieval from brightness temperature through a convergence loop
• Comparing model (guessed SSS) with measurements at all incidence angles
• Sea surface emissivity model (top 1 cm) including roughness effects
• Other contributions from external sources and atmospheric effects
• Need for auxiliary data to describe environmental conditions
Tb,p = Tb,p flat (θ, SST, SSS) + Tb,p rough (θ, Ф, wind waves, swell, other wave characteristics, foam coverage, foam emissivity, rain)
Ocean
Atmosphere
IGARSS 2010, Honolulu, July 25-30, 2010 5
• L2 accuracy estimated during algorithm validation- 1-2 psu range
- function of distance to track - depending on environmental
variables
SMOS SSS retrieval expectations
• Mission requirements to be reachable through spatio-temporal averaging (level 3)
IGARSS 2010, Honolulu, July 25-30, 2010 6
The SMOS L2 OS processor
Retrieved SSS along a SMOS ascending orbit in the Pacific Ocean. Unfiltered (left) and filtered (right, removing flagged data) values
Developed by the SMOS L2 OS team and implemented by Argans Ltd., UK
IGARSS 2010, Honolulu, July 25-30, 2010 7
• Bias in the comparison of measured and modeled Tb
– Spatial pattern persistent along and in different orbits– Similar using different ocean emissivity models: related to instrument
and image reconstruction imperfections
– Removal techniques being tested: the Ocean Target Transformation (OTT, mean residual bias over homogeneous ocean areas)
Main problems in SSS retrieval
(see talk by M. Talone, Friday)
IGARSS 2010, Honolulu, July 25-30, 2010 8
First salinity map
• Comparing SSS map generated with 3 days of SMOS data (ascending
orbits 29-31 Jan 2010, using OTT derived in December) and WOA
climatology for January (simplified retrieval, not SMOS L2 processor)• No data averaging• Degraded results in FOV borders, near coast, and in areas of strong
wind
by J. Tenerelli, CLS, Brest, 10 Feb 2010
IGARSS 2010, Honolulu, July 25-30, 2010 9
Amazon plume detected by SMOS
• SMOS descending orbits, March 2010
• In situ March climatology (1977-2002) @ 1°x1° (G. Reverdin, LOCEAN)
by N. Reul, IFREMER, Brest
IGARSS 2010, Honolulu, July 25-30, 2010 10
• Impact of land on Tb bias patterns
Main problems in SSS retrieval
by J. Tenerelli & N. Reul
IGARSS 2010, Honolulu, July 25-30, 2010
TY browse
• Contamination from radio frequency interferences (RFI)
Main problems in SSS retrieval
11SSS descending 10-25 July
IGARSS 2010, Honolulu, July 25-30, 2010 12
S-N SSS anomaly in the Pacific: comparing SMOS and ARGO
0.1 degree bin in latitude, all grids across swath
- 1 SMOS half orbit on 11 December 2009
- World Ocean Atlas 2005 SSS climatology
- Monthly ISAS analysis of ARGO surface fields in December 2009, Gaillard, LPO, 2010
Latitudinal SSS gradients
by J. Boutin & X. Yin, LOCEAN, Paris
IGARSS 2010, Honolulu, July 25-30, 2010 13
Combining several SMOS orbits
• Weekly global salinity map, July 2010: weighted averaging + discarding flagged data
by M. Talone, SMOS-BEC, Barcelona
(see talk by R. Sabia,
this afternoon)
IGARSS 2010, Honolulu, July 25-30, 2010 14
Comparing different OTTs
SSS anomaly (misfit between retrieved and monthly climatology) by using a single half-orbit OTT
SSS anomaly by using a model-independent biasmitigation technique
by J. Gourrion, SMOS-BEC, Barcelona
WARNING: New Flat Target Transformation July 2010
(see talk by M. Talone, Friday)
IGARSS 2010, Honolulu, July 25-30, 2010 15
Checking processing options
Sea surface salinity from ten days of combined orbits in the eastern Pacific using only the Alias-Free Field-of-View and the three roughness models
by A. Chuprin, Argans Ltd., Plymouth
IGARSS 2010, Honolulu, July 25-30, 2010
a square of 0.25 in instrument coordinate,about 600 * 600 km,(smaller biases and noise)
5 day, SMOS SSS (17-21March, 2010) ascending orbitsOnly Tb measurements in a square in center of FOV, cleanest Tb
16
Analysis of SMOS AF-FOV data
by J. Boutin & X. Yin, LOCEAN, Paris
IGARSS 2010, Honolulu, July 25-30, 2010
SMOS
╂ Argo
Monthly ISAS analysis of ARGO surface fields of March, 2010 ( F. Gaillard)
5-day SMOS SSS: covers areas not sampled by Argo in one month
5-day mean SSS onboard TAO (tropical atmosphere ocean project) moorings (16 -20 March, 2010)
17
Multi-orbit SMOS vs. in situ
IGARSS 2010, Honolulu, July 25-30, 2010
Possible reasons for discrepancy1) SMOS sees 5-day mean SSS at 1 cm depth, while
WOA and ISAS SSS are monthly average2) Is bias removal strategy robust enough?
SMOS - WOA05
SSS of SMOS, WOA05 and ARGO/ISAS averaged into 0.5° bin in latitude
18
SMOS and in situ SSS anomalies
IGARSS 2010, Honolulu, July 25-30, 2010 19
Validation of SMOS L2 products
Preliminary global validation: • March 2010: comparison of SMOS data
composite with 7296 in situ salinity values (Argo floats)
• ~0.5 psu accuracy @ 0.25° resolution
by N. Reul, IFREMER, Brest
Validation using L3, J. Ballabrera, SMOS-BEC, Barcelona (see talk by J. Gourrion this afternoon)
IGARSS 2010, Honolulu, July 25-30, 2010 20
Status of SMOS SSS retrieval
Ongoing studies on:• Bias removal techniques• Land and RFI contamination mitigation• Forward models improvement• Salinity maps generation and validation• July 2010: data to Cal/Val teams
See detailed presentations:
TH3.L02.1 Sabia et al. SMOS measurements preliminary validation against modeled brightness temperatures and external-source salinity data
TH3.L02.2 Gourrion et al. Preliminary validation of SMOS products (levels 3 and 4)
FR2.L10.5 Talone et al. SMOS brightness temperatures validation: first results after the commissioning phase
SMOS SAG, ESAC, 15-16 March 201021 / 10
COST Action network
Coordinate pan-European teams to define common protocols to produce high-level salinity maps and related products, and broaden expertise in their use for operational applications.
Benefits• Unify disperse knowledge and efforts• Define standardized data processing protocols • Address problems with high societal/industrial
impacts
SMOS-MODE SMOS Mission Oceanographic Data Exploitation
Schedule
• Sep.09: Preliminary proposal
• Nov.09: Selected for full-proposal
• Mar.10: Selected for hearing session
• Jun.10: Approved!
Dr. Christine Gommenginger,
ENG
Dr. Roberto Sabia, SPA
Dr. Alexander Ostrovskii,
RUS
Prof. Ana Martins, POR
Prof. Johnny Johannessen,
NOR
Prof. Aldo Drago, MAL
Dr. Pierre-Marie Poulain, ITA
Dr. Brian Ward, IRE
Dr. Gerasimos Korres, GRE
Dr. Nicolas Reul, FRA
Dr. Juha Kainulainen,
FIN
Dr. George Zodiatis, CYP
SMOS SAG, ESAC, 15-16 March 201022 / 10
Thank you for your attention!
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