The Impact of Combining SMOS and ARGO Data on the SMOS …microrad2008.cetem.org/public/presentations/20080312_11... · 2011-02-03 · Introduction. At IGARSS’07, July 23. rd-27

The Impact of Combining SMOS and ARGO Data on the SMOS Level 2 and 3 Products and

Effect of the Vicinity of the Coast

μRAD 2008 –

Firenze 12/03/08

M. Talone(1,3), A. Camps(1,3), B. Mourre(2,3), R. Sabia(1,3), M. Vall-llossera(1,3), C. Gabarró(2,3), J. Font(2,3)

(1) Remote Sensing Laboratory Departament Teoria del Senyal i Comunicacions (TSC)

Universitat Politècnica de Catalunya (UPC), Barcelona, Spain

(2) Institut de Ciències del Mar (ICM-CMIMA) - CSICBarcelona, Spain

(3) SMOS–BEC, Barcelona, Spain

μRAD 2008 –

Firenze

12/03/08 Marco Talone –

R.S.Lab UPC

ContentsContents

1/20

• IntroductionIntroduction

•• ObjectivesObjectives

•• Simulation SettingsSimulation Settings

•• Simulation ResultsSimulation Results•• Performance at Level 2Performance at Level 2•• Performance at Level 3Performance at Level 3•• Coast effect at Level 2Coast effect at Level 2•• Coast effect at Level 3Coast effect at Level 3

•• ConclusionsConclusions

μRAD 2008 –

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IntroductionIntroductionAt IGARSS’07, July 23rd-27th

2007Using • Ad-hoc geophysical parameters• SMOS End-to-end Performance Simulator (SEPS)• Level 2 Processor Simulator (L2PS)

“External Brightness Temperature Calibration”[*]

“External Salinity Calibration”[**]

Have been tested for an Academic Case, and succeeded allowing retrieving SSS gradients up to 1 psu/10º

of latitude

Next Step:Try a realistic scenario

2/20

[*] Camps et al., I., “Retrieving Sea Surface Salinity With Multi-Angular L-band Brightness Temperatures: Improvement By Spatio-Temporal Averaging”, Radio Science, vol. 40, March 2003.Camps et al., “Improved Image Reconstruction Algorithm for Aperture Synthesis Radiometers”

IEEE Transactions on Geoscience

and Remote Sensing vol. 46, no. 1, pp 146-158, Jan. 2008

[**]

Talone et al., “Towards a Coherent Sea Surface Salinity Product from SMOS Radiometric Measurements and ARGO Buoys”

Proceedings IGARSS 07, pp. 3959-3962

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ObjectivesObjectives

• Simulate realistic situationsSimulate realistic situations

Ocean surface geophysical parameters generatedOcean surface geophysical parameters generatedusing the using the OcOcééan Parallan Paralléélisliséé

(OPA(OPA[*][*]) model) model

SMOSSMOS--like brightness temperatures generated like brightness temperatures generated using SEPS (including instrument errors, using SEPS (including instrument errors, calibration, image reconstructioncalibration, image reconstruction……))

•• Test the performance Level 2 and 3 Test the performance Level 2 and 3 3030--day (1day (1ººx1x1ºº) and 10) and 10--day (2day (2ººx2x2ºº) products) products

•• Assess the impact on the Coast Proximity Effect at Level 2 and Assess the impact on the Coast Proximity Effect at Level 2 and 33

3/20

SSS SST

[*]

Mourre, B. et al., “Surface salinity response to forcing and parameter perturbations

in a climatological

simulation of the eastern North-Atlantic Ocean”, Ocean Modelling

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IntroductionIntroduction

––

Level 2 Retrieval AlgorithmLevel 2 Retrieval Algorithm

SSS has been retrieved using the Level 2 ProcessorSimulator (L2PS), according to the minimization of thefollowing cost function:

( ) ( )2

21010

2

2

12

2

2

10

1

U

aux

SST

auxN

n F

modeln

measn

obs

UUSSTSSTFFN

obs

nσσσ

χ −+

−+

−= ∑

=

[ ]Thv TTF ,= [ ] [ ] [ ]yxvh TTTTIF +=+==where or

Same models used in the forward model (SEPS) are used to compute modelnF

better to compute in the antenna frame, where the singularities due to the transformation from antenna to Earth frame are avoided.

4/20

μRAD 2008 –

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R.S.Lab UPC


––

The External CalibrationsThe External Calibrations

( ) ( )θθ ,,,,,, 1010 auxauxauxmod

Borigorigorigmeas

BB USSTSSSTUSSTSSSTT −=Δ

Bmeas

Bcorrected

B TTT Δ−=

Using the auxiliary data as input to compute a brightness temperature image.The mean of the difference between the measured temperature and the modeled one is considered bias:

The new brightness temperature is given by the subtraction between the measured brightness temperature and the bias:

retrinst SSSSSSCF =

retrcorr SSSCFSSS ⋅=

The CF has been calculated taking into account only the points observed more than 40 times (eliminating the noisiest points).

The final retrieved SSS is thus given by:

Once the Sea Surface Salinity map is retrieved, to correct for the errors introduced by the forward models inaccuracies ( εr

, sea state dependence…

), a Calibration Factor is calculated as in rain radar[*]:

5/20

Ext

erna

l Brig

htne

ss

Tem

pera

ture

Cal

ibra

tion

Ext

erna

l Sal

inity

C

alib

ratio

n

[*]

Seo, D.J. and Breidenbach, J.P., “Real-time correction of spatially non-uniform bias in radar rainfall data using rain gauge measurements”, Journal of Hydrometeorology, vol. 3, pp. 93-111, 2002

μRAD 2008 –

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––

The External CalibrationsThe External Calibrations

SEPS

L2PS

External External BrightnessBrightness

Temperature Temperature CalibrationCalibration

External External Salinity Salinity

CalibrationCalibration

2χ

Sea Surface Salinity Maps

Brightness Temperatures

“True”Data

AuxiliaryData

6/20

Instant.Data

μRAD 2008 –

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Simulation SettingsSimulation Settings

7/20

30º W60º W

60º N

0º

30º N

30º W60º W

60º N

0º

30º N

Three data-sets have been defined

• Real Data (SEPS forward models)

• Auxiliary Data (a priori information)

• Instantaneous Data (in situ data)

Total Argo buoys observations between 2001 and june

2007 in uniform grid 2ºx2º

Real Data

SSS -

OPA

SST -

OPA

WS -

ECMWF year

2000

Aux. Data

SSS -

Levitus

SST -

Levitus

WS -

NCEP-COREyear

2000

Inst. Data

SSS –

Argo(OPA)

+ VOS(OPA)

μRAD 2008 –

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Simulation SettingsSimulation Settings

OPEN-OCEAN COASTAL( )

( )NNlongitudeWWlatitude

27,941,27

∈∈

From March 1st

to 31st, 2007 (SEPS-time)64 overpassesMore than 1500 snapshots

( )( )NNlongitude

WWlatitude40,20

20,5∈

∈

From March 1st

to 31st, 2007 (SEPS-time)69 overpassesMore than 1700 snapshots

8/20

K 48.0=SSTσ m/s 6.110 =UσK 81.0=SSTσ m/s 6.110 =Uσ

μRAD 2008 –

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Simulation Results Simulation Results --

L2L2

9/20

OPEN OCEAN 63rd

overpass –

March 31st

7:47 GMT

error [psu]

no. o

fsam

ples

error [psu]no

. ofs

ampl

es

mean error 0.203 psu

std.dev

0.789 psu mean error 0.003 psu

std.dev

0.789 psu

Retrieved

SSS

Auxiliary

SSS

Original SSS

Error in SSS

Only external brightness temperature calibration

Both external brightness temperature and salinity calibration

Retrieved

SSS

Auxiliary

SSS

Original SSS

Error in SSS

μRAD 2008 –

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R.S.Lab UPC


L2L2

10/20

COASTAL ZONE 19th

overpass –

March 9th

19:11 GMT

error [psu]

no. o

fsam

ples

error [psu]no

. ofs

ampl

es

mean error -0.30 psu

std.dev

1.27 psu mean error -0.02 psu

std.dev

1.28 psu

Retrieved

SSS

Auxiliary

SSS

Original SSS

Error in SSS


Both external brightness temperature and salinity calibration

Retrieved

SSS

Auxiliary

SSS

Original SSS

Error in SSS

μRAD 2008 –

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R.S.Lab UPC


L2L2

11/20

OPEN-OCEAN COASTAL

1 psu

1 psu

Only

externalbrightness

temperaturecalibration

Both

externalbrightness

temperatureand salinitycalibration

mea

n er

ror

std.

dev

r.m.s

.m

ean

erro

rst

d.de

vr.m

.s.

mea

n er

ror

std.

dev

r.m.s

.m

ean

erro

rst

d.de

vr.m

.s.

overpass overpass

overpass overpass

1 psu

1 psu

μRAD 2008 –

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R.S.Lab UPC

Simulation Results Simulation Results ––

Open OceanOpen Ocean

10-day L3 (1st-10th

of March) 2ºx2º

12/20

Original SSS Retrieved

SSS SSS Retrieval

Error Error statistics

latit

ude

[º]

longitude

[º]

latit

ude

[º]

longitude

[º]

latit

ude

[º]

longitude

[º]

latit

ude

[º]

longitude

[º]

latit

ude

[º]

longitude

[º]

error [psu]

no. o

fsam

ples


std.dev

0.26 psu

error [psu]

no. o

fsam

ples


std.dev

0.26 psu

μRAD 2008 –

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Open OceanOpen Ocean

13/20

30-day L3 1ºx1º


SSS SSS Retrieval

Error Error statistics

latit

ude

[º]

longitude

[º]

latit

ude

[º]

longitude

[º] longitude

[º]

longitude

[º] longitude

[º]

latit

ude

[º]

latit

ude

[º]la

titud

e[º]

error [psu]

no. o

fsam

ples


std.dev

0.16 psu

error [psu]

no. o

fsam

ples


std.dev

0.16 psu

μRAD 2008 –

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R.S.Lab UPC


CoastalCoastal

14/20

10-day L3 (1st-10th

of March) 2ºx2º


SSS Error statistics

latit

ude

[º]

longitude

[º]

latit

ude

[º]

longitude

[º] longitude

[º]

longitude

[º] longitude

[º]

latit

ude

[º]

latit

ude

[º]la

titud

e[º]

error [psu]

no. o

fsam

ples


std.dev

0.33 psu

error [psu]

no. o

fsam

ples


std.dev

0.33 psu

SSS Retrieval

Error

μRAD 2008 –

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R.S.Lab UPC


CoastalCoastal

30-day L3 1ºx1º

15/20


SSS Error statistics

latit

ude

[º]

longitude

[º]

latit

ude

[º]

longitude

[º] longitude

[º]

longitude

[º] longitude

[º]

latit

ude

[º]

latit

ude

[º]la

titud

e[º]

error [psu]

no. o

fsam

ples


std.dev

0.30 psu

error [psu]

no. o

fsam

ples


std.dev

0.30 psu

SSS Retrieval

Error

μRAD 2008 –

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Coast effectCoast effect

16/20

The coast proximity effect at Level 2 –

error r.m.s.2D histrogram

error vs

distance & number of observations

The error r.m.s. decreases just 5% (~0.15 psu

over 3 psu) in the zone closer to the coast


Both external brightness temperature and salinity

calibration

calibrated -

not calibratedmean error

distance

from

the

coast

[km]

num

bero

fobs

erva

tions

distance

from

the

coast

[km]

num

bero

fobs

erva

tions

distance

from

the

coast

[km]

num

bero

fobs

erva

tions

0

5

0

5

-0.5

0.5

μRAD 2008 –

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R.S.Lab UPC17/20




Mean Error2D histrogram

error vs

distance & number of observations

The mean error improves by 10%

(~0.1 psu

over 1 psu) when N > 30 observations



calibration

calibrated -

not calibratedmean error

distance

from

the

coast

[km]

num

bero

fobs

erva

tions

distance

from

the

coast

[km]

num

bero

fobs

erva

tions

distance

from

the

coast

[km]

num

bero

fobs

erva

tions

0

5

0

5

-0.5

0.5

μRAD 2008 –

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R.S.Lab UPC18/20




10-days product

Performance improves only of a few % of psu

(2-4%)


distance

from

the

coast

[km]


calibration

Err

or in

the

retri

eved

SSS

[psu

]

distance

from

the

coast

[km]

Err

or in

the

retri

eved

SSS

[psu

]

μRAD 2008 –

Firenze


R.S.Lab UPC19/20




30-days product


distance

from

the

coast

[km]


calibration

Err

or in

the

retri

eved

SSS

[psu

]

distance

from

the

coast

[km]

Err

or in

the

retri

eved

SSS

[psu

]

Performance improves only of a few % of psu

(2-4%)

μRAD 2008 –

Firenze


R.S.Lab UPC

ConclusionsConclusions

20/20

L2 Products:

•

External Salinity Calibration remarkably reduces the retrieved SSS mean error, while std error remains constant.

•

Coast proximity degrades the performance of the SSS retrieval (std error) by factor 1.5 –

2: large errors (> 1.5 -

2 psu) found up to 150 km from the coast.

•

External Salinity Calibration slightly decreases the error induced by the coastal proximity: 10% for mean error and 5% for rms.

L3 Products:

•

Mean error is reduced by 25% for 10-day products and 10% in 30-day ones.

•

The impact of the External Salinity Calibration on the Coast Proximity effect is negligible (2-4 %)

•

L3 mean error dominated by std error at L2

•

L2→L3 averaging techniques not fully optimized: physical constraints not yet included, all pixels are considered so far….

Thank you very much for your attention!

error [psu]

no. o

fsam

ples

mean error -0.16

std.dev

0.31

error [psu]

no. o

fsam

ples

mean error -0.20

std.dev

0.32

10 days

Open-Ocean

Tb

Tb

+ SSS

error [psu]

no. o

fsam

ples

mean error -0.16

std.dev

0.18

1 month

Open-Oceanerror [psu]

no. o

fsam

ples

mean error -0.15

std.dev

0.18

Tb

Tb

+ SSS

error [psu]

no. o

fsam

ples

mean error -0.16

std.dev

0.48

error [psu]

no. o

fsam

ples

mean error -0.23

std.dev

0.48

10 days

Coastal

Tb

Tb

+ SSS

error [psu]

no. o

fsam

ples

mean error -0.20

std.dev

0.37

error [psu]

no. o

fsam

ples

mean error -0.27

std.dev

0.37

1 month

Coastal

Tb

Tb

+ SSS

Documents

The Impact of Combining SMOS and ARGO Data on the SMOS …microrad2008.cetem.org/public/presentations/20080312_11... · 2011-02-03 · Introduction. At IGARSS’07, July 23. rd-27