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Large scale SSS inter-annual variability in tropical Indian and Pacific Oceans. J. Boutin 1 , O. Hernandez 1 , N. Martin 1 , G. Reverdin 1 , F. Gaillard 2 , S. Morrisset 1 1 CNRS/LOCEAN (CNRS-UPMC-IRD) Paris, France 2 IFREMER/LPO (CNRS-Ifremer-IRD-UBO), Plouzané, France

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large scale sss inter annual variability in tropical indian and pacific oceans

Large scale SSS inter-annual variability in tropical Indian and Pacific Oceans

J. Boutin1, O. Hernandez1, N. Martin1, G. Reverdin1, F. Gaillard2, S. Morrisset1

1 CNRS/LOCEAN (CNRS-UPMC-IRD) Paris, France

2 IFREMER/LPO (CNRS-Ifremer-IRD-UBO), Plouzané, France

+ collaborations with

French GLOSCAL SMOS Cal/Val project

QWG10, Boutin & Hernandez

slide2

Introduction

2010  : Strong la Niña and negative phase of the Indian Ocean Dipole (IOD)

Strong la Niña

-IOD

These events are known to generate large scale SSS anomalies in the tropics

(e.g. Gouriou et Delcroix, 2002, Singh et al. 2011, Grunseich et al. 2011)

QWG10, Boutin & Hernandez

data methods
Data & Methods

DATA:

SMOS SSS

ESA v5 reprocessing; monthly maps averaged as in (Boutin et al., TGRS, 2012)

ARGO + TSG OPTIMAL INTERPOLATED SSS MAPS (ISAS)

Monthly maps from In-Situ Analysis System v6 (F. Gaillard, LPO/IFREMER, pers. Comm.)

http://wwz.ifremer.fr/lpo/SO-Argo/Products/Global-Ocean-T-S

SEA SURFACE AUTONOMOUS DRIFTERSSS

Upper S at 45cm depth; Pacific Gyre drifter (Reverdin and Morrisset, LOCEAN)

http://www.locean-ipsl.upmc.fr/smos/drifters

METHOD:

COMPARISON OF SSS ANOMALIES BETWEEN 2010 AND 2011 AS DERIVED BY ISAS AND BY SMOS

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slide4

High contrasted SSS signal between 2010 and 2011

July 2011-2010

November 2011-2010

  • Good consistence between SMOS 2011-2010 SSS differences and ISAS 2011-2010 SSS differences
  • In the Pacific Ocean, 2011 - 2010 SSS differences associated with displacement of the ITCZ and SPCZ

QWG10, Boutin & Hernandez

slide5

High contrasted SSS signal between 2010 and 2011

July 2011-2010

November 2011-2010

+

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+

+

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SSS Anomaly (1975 – CLM )

  • Good consistence between SMOS 2011-2010 SSS differences and ISAS 2011-2010 SSS differences
  • In the Pacific Ocean 2011 - 2010 SSS differences associated with displacement of the ITCZ and SPCZ
  • In the Indian Ocean : SSS differences consistent with SSS anomalies reported during negative IOD coupled with Strong La niña event (Grunseich et al. 2011)

QWG10, Boutin & Hernandez

Grunseich et al. 2011

slide6

High contrasted SSS signal between 2010 and 2011

July 2011-2010

November 2011-2010

+

-

+

+

-

+

SSS Anomaly (1975 – CLM )

  • Good consistence between SMOS 2011-2010 SSS differences and ISAS 2011-2010 SSS differences
  • 2011 - 2010 SSS differences associated with displacement of the ITCZ and SPCZ
  • In the Indian Ocean : SSS differences consistent with SSS anomalies reported during negative IOD coupled with Strong La niña event (Grunseich et al. 2011)

+

-

+

QWG10, Boutin & Hernandez

Grunseich et al. 2011

at first order good consistency in smos and isas 2011 2010 variability but
At first order good consistency in SMOS and ISAS 2011-2010 variability but...

July 2011-July2010 November 2011-November 2010

ISAS

SMOS

Larger contrasts on SMOS SSS anomalies than on ISAS SSS anomalies

Why? effect of ARGO/TSG undersampling (=> OI smoothing) and/or a systematic underestimate of SMOS SSS in low SSS/rainy/stratified regions?

QWG10, Boutin & Hernandez

2011 2010 sss in n trop pac 5 n 15 n
2011-2010 SSS in N. Trop. Pac. (5°N-15°N)

SSS anomaly July 2011-2010

SSS July 2010

ISAS

SMOS

Larger westward extent of the fresh SSS as seen by SMOS than by ARGO : stratification or ARGO undersampling?

QWG10, Boutin & Hernandez

2011 2010 sss in 30 s 0 n region
2011-2010 SSS in 30°S-0°N region

July 2011-July2010

ISAS

SMOS

Larger contrasts on SMOS SSS anomalies than on ISAS SSS anomalies

QWG10, Boutin & Hernandez

2011 2010 sss in 30 s 0 n region1
2011-2010 SSS in 30°S-0°N region

July 2011-July2010

July2010

ISAS

SMOS

Larger contrasts on SMOS SSS anomalies than on ISAS SSS anomalies

Fresh region in 2010 fresher on SMOS than ISAS and very few ARGO in fresh region

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june 2010 sss in 30 s 0 n region surface autonomous drifter s at 45cm depth
June 2010 SSS in 30°S-0°N regionSurface autonomous drifter (S at 45cm depth)

June 2010

SSS ISAS

ISAS MONTHLY

SSS SMOS

SMOS MONTHLY

DRIFTER

Again fresh region in 2010 fresher in SMOS than in ISAS maps

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summary
Summary
  • At first order, strong 2011-2010 SSS interannual variability in tropical oceans consistently seen by SMOS and ARGO 
  • At first order, in the Pacific Ocean, strong 2011-2010 SSS differences associated with displacement of the ITCZ and SPCZ during La Niña event ; in the Indian Ocean : SSS differences consistent with SSS anomalies already reported during negative IOD coupled with Strong La Niña event
  • 1°x1° 10 days & monthly SMOS SSS (1cm depth) fresher than ARGO & ISAS SSS (~5m depth) in rainy regions : 2 hypothesis:
          • surface stratification and rain effect
          • In situ undersampling and OI smoothing
  • To go further:
    • -apply a similar smoothing to SMOS and ARGO measurements
    • -look at 2012...

QWG10, Boutin & Hernandez

extra slides
EXTRA SLIDES

QWG10, Boutin & Hernandez

slide15

SSS SMOS

Precipitation impact on large scale SSS variability

November 2011-2010

?

  • 2011 - 2010 SSS differences associated with displacement of the ITCZ and rainy regions
  • In the Indian Ocean : Saltier SSS in 2010 associated with smaller rain rate during preceding month
  • High anomaly around Madagascar not consistent with rainy events.

RAIN RATE

October 2011-2010

?

November 2011-2010

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