Sea_Surface_Salinity_and_Lband_Radiometric_measurements_CAROLS_SMOS.pdf

L-BAND R ADIOMETRIC M EASUREMENTS IN THE
G ULF OF B ISCAY: SMOS AND CAROLS

A. Martin1 , J. Boutin1 , D. Hauser2 , G. Reverdin1 , M. Pardé2 ,
M. Zribi2,3 , P. Fanise2,3 , X. Yin1 , J. Tenerelli6 , N. Reul5

1 LOCEAN-IPSL, Paris
2 LATMOS-IPSL, Paris
3 CESBIO, Toulouse
5 IFREMER, Plouzané
6 CLS, Plouzané

Adrien MARTIN (LOCEAN-IPSL) SMOS & CAROLS IGARSS Vancouver 2011 1 / 25

O BJECTIVES
CAROLS — VALIDATION FOR SMOS

ATR42 - SAFIRE

Synergy between passive & active
microwave data
Comparison of SMOS and
SMOS CAROLS data in the Gulf of
Biscay


SMOS AND CAROLS F LIGHT T RACK
A IRBORNE C AMPAIGN N OVEMBER 2010

19 Nov. asc.
22 Nov. des.
25 Nov. des.
27 Nov. asc.

ACQUISITION T IME :
25 N OV.
CAROLS: 18 to 23 UTC
SMOS: 18:45 UTC
November 25, 2010 — Gulf of Biscay


O UTLINE

1 A IRBORNE ACQUISITION
Airborne Instruments
Geophysical conditions
L-band Brigthness Temperature

2 SMOS
Retrieved SSS
Tb Analysis


O UTLINES


2 SMOS
Retrieved SSS
Tb Analysis


A IRBORNE I NSTRUMENTS

CAROLS L-band (21cm) radiometer
STORM C-band (5.6cm) scatterometer


CAROLS

CAROLS Radiometer (derived from EMIRAD 2)
[Zribi et al., 2011]
Correlation radiometer with direct sampling
Fully polarimetric (i.e 4 Stockes)
Freq : - 3 dB @ 1401 MHz 1426 MHZ
Sensitivity : 0.1 K for 1 s integration time CAROLS Antenna
(300K target)
Stability: better than 0.1K over 15 min
Internal calibration : load and noise diode
A large potter horn (HPBW 37.6◦ ) at 34◦
Cables with low loss and well monitored
temperature
CAROLS OMT


CAROLS
G ULF OF B ISCAY — 25 N OVEMBER 2010

Tb P ROCESSED AT LATMOS
correction for cable attenuation and reﬂexion
sorting out RFI (kurtosis method)

T HIS W ORK
Tb averaged on 1s
keep incidence angles ∈ [33.3o ; 34.3o ]
then averaged on ≈2 min centered on
STORM measurements
use V and H polarizations


STORM — C- BAND S CATTEROMETER

high wind speed

low wind speed

C-band radar (5.6 cm)
antenna rotation (360˚/min)
incidence range 5 to 35◦ σ 0 vs. incidence angle


O UTLINES


2 SMOS
Retrieved SSS
Tb Analysis


G EOPHYSICAL C ONDITIONS

in situ SSS STORM deduced Wind CAROLS L-band
Speed (VV at 30◦ ) Brightness Temperature
H-pol

SST = 12-15˚C


O UTLINES


2 SMOS
Retrieved SSS
Tb Analysis


B RIGHTNESS T EMPERATURES S IMULATIONS
TRAP: T ERRESTRIAL R ADIOMETRY A NALYSIS PACKAGE SOFWARE

M ODELING L- BAND R ADIOMETER S IGNAL
Sea Surface Emissivity
for a ﬂat surface [Klein and Swift, 1977]
contribution of Roughness (two-scale model) [Dinnat et al., 2003]
Atmospheric Emissivity and Absorption [Liebe et al., 1993]
Modeling of SMOS Tbs
Scattering of sky radiation by Sea Surface [Tenerelli et al., 2008]
• Tb = Tbatm! + Rsea (Tbatm" + Tbsky) exp(-τatm) + Tbsea exp(-τatm)

M ODELING CAROLS A NTENNA
T EMPERATURE
Atmosphere CAROLS antenna lobes
geometry
aircraft attitude
Tbsea= (Tbflat+Tbrough) (1-F) + F Tbfoam
Tbsea=esea SST
5 m/s ≈ 1K
Ocean
esea derived from SMOS Tbs after correcting for all other effects

B RIGHTNESS T EMPERATURE D EPENDENCE ON W IND

Measure Tb (V and H-polarization) vs. Wind Speed


Time biases on Tb around 0.5K


S CATTERED G ALACTIC N OISE ALONG THE FLIGHT

Modeled Scattered Galactic Noise


S CATTERED G ALACTIC N OISE D EPENDENCY

Scattered Galactic Noise Dependency


A FTER REMOVING ALL MODELED DEPENDENCY

δTb = Tbmeasured − Tbmodeled (WS = 5ms−1 )

δTb vs. Wind Speed


O UTLINES


2 SMOS
Retrieved SSS
Tb Analysis


SMOS DATA

Last L1 (Roger Oliva pers. L2 RFI ﬂags equal to 1 if:
com.) and L2 processing
2 2
σrad + σmod
(v500) std(Tbmeas−OTT − Tbmod ) > 1.2
N


O UTLINES


2 SMOS
Retrieved SSS
Tb Analysis


SMOS S NAPSHOT

AFFOV & EAFFOV H in the satellite frame V in the satellite frame


SMOS — T B A NALYSIS

EAFFOV EAFFOV

Southest Block Northest Block


C ONCLUSIONS & P ERSPECTIVE

C ONCLUSIONS
High correlation between Brightness Temperature and
scatterometer Wind Speed;
SMOS data, highly polluted by RFI in the Gulf of Biscay for
descending orbit.

P ERSPECTIVE
Analysis other flights of the November 2010 campaign;
Looking at the ascending orbite in the Gulf of Biscay;
Study the influence of Land contamination;
Further validate the galactic scattering model using other
CAROLS flights.


Dinnat, E., Boutin, J., Caudal, G., and Etcheto, J. (2003).
Issues concerning the sea emissivity modeling at L band for
retrieving surface salinity.
Radio Science, 38(4):8060.
Klein, L. and Swift, C. (1977).
An improved model for the dielectric constant of sea water at
microwave frequencies.
IEEE Journal of Oceanic Engineering, 2(1):104–111.
Liebe, H., Hufford, G., and Cotton, M. (1993).
Propagation modeling of moist air and suspended water/ice
particles at frequencies below 1000 GHz.
In AGARD, Atmospheric Propagation Effects Through Natural and
Man-Made Obscurants for Visible to MM-Wave Radiation.
(SEE N94-30495 08-32).
Tenerelli, J., Reul, N., Mouche, A., and Chapron, B. (2008).
Earth-viewing L-band radiometer sensing of sea surface scattered
celestial sky radiation-Part I: General characteristics.

IEEE Transactions on Geoscience and Remote Sensing,
46(3):659–674.
Zribi, M., Parde, M., Boutin, J., Fanise, P., Hauser, D., Dechambre,
M., Kerr, Y., Leduc-Leballeur, M., Reverdin, G., Skou, N., et al.
(2011).
CAROLS: A New Airborne L-Band Radiometer for Ocean Surface
and Land Observations.
Sensors, 11:719–742.


Sea_Surface_Salinity_and_Lband_Radiometric_measurements_CAROLS_SMOS.pdf

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