TH2.L10.2: OVERVIEW OF SMOS LEVEL 2 OCEAN SALINITY PROCESSING AND FIRST RESULTS

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

[email protected]


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)


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


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


• 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)


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


• 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)


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


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


• Impact of land on Tb bias patterns


by J. Tenerelli & N. Reul

IGARSS 2010, Honolulu, July 25-30, 2010

TY browse

• Contamination from radio frequency interferences (RFI)


11SSS descending 10-25 July


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


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)


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)


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


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


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)

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Multi-orbit SMOS vs. in situ


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

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SMOS and in situ SSS anomalies


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)


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!

TH2.L10.2: OVERVIEW OF SMOS LEVEL 2 OCEAN SALINITY PROCESSING AND FIRST RESULTS

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