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The “CIRENE” campaign Jan-Feb 2007. P.I. J. Vialard [email protected] A brief summary. Where? In the western Indian Ocean, between 5°S and 10°S When? In January-February 2007 Why? To study the strong SST response to the MJO in this region. MJO & oceanic response.

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A brief summary
A brief summary

  • Where?

    In the western Indian Ocean, between 5°S and 10°S

  • When?

    In January-February 2007

  • Why?

    To study the strong SST response to the MJO in this region.

The Cirene project

Mjo oceanic response
MJO & oceanic response

  • Intraseasonal variability of the convection

    • Summer: active & break phases of the monsoon

    • Winter: MJO

  • Many recent studies indicate strong SST responses & possible feedback: e.g. Sengupta & Ravichandran, 2001; Harrison and Vecchi 2001; Duvel et al. 2004; Duvel and Vialard, 2006; Vecchi and Harrison, 2002; etc…

Contours: mean OLR Colors: 10-80 day standard deviation

The Cirene project

Sst response to the mjo
SST response to the MJO

  • Case study: Duvel et al. (2004)

One of the 2 strong SST

signals due to the MJO

in early 1999

The Cirene project

Observed SST response associated with large-scale OLR 10-80 day variability



SST response to the MJO

  • Statistical study: Duvel and Vialard (2006)

No strong SST response in western Pacific

Other region of strong SST response

« Cirene  region »

The Cirene project

Sst response to the mjo1
SST response to the MJO day variability

  • Duvel and Vialard (2006)

    The 53°E-81°E, 3°S-9°S region is highly responsive to MJO in winter (especially in January)

    15-day low passed filtered time series of TMI SST, NOAA OLR, NCEP surface wind and heat fluxes in the CIRENE region

The Cirene project

Sst response to the mjo2

1D Modelling of the role of diurnal cycle in COARE day variability

Modèle 1D

(Bernie et al. 2005)

SST response to the MJO

  • Probably largely driven by heat fluxes (solar and latent) but questions remain on the role of vertical mixing and Ekman pumping.

  • Models and re-analyses don’t allow to close budget (underestimation of variability)

  • Role of diurnal cycle?

The Cirene project

Scientific questions
Scientific questions ? day variability

Coupling between SST and convection at intraseasonal scale in winter in the “Cirene” region.

  • Processes driving the SST

    • Respective role of fluxes / Ekman pumping and mixing?

    • Role of the diurnal cycle?

    • Role of thermocline in maintaining shallow mixed layer

    • Why such a warm SST in a shallow thermocline & upwelling region?

  • Biogeochemical response of the ocean to the MJO

    • Chlorophyll-a signal?

    • Influence on the heat budget?

  • Ocean feedback on the atmosphere?

    • Influence of local against large scale conditions?

The Cirene project

Two components
Two components day variability

  • The Vasco experiment (PI: J-P. Duvel)

    • Deployment of Aeroclippers and pressurised baloons from the Seychelles (Jan-Feb 2007)

  • The Cirene experiment (PI: J. Vialard)

    • Oceanographic campaign with the Ifremer ship « Le Suroît », starting from the Seychelles (Jan-Feb 2007)

The Cirene project

Two components1
Two components day variability

VASCO aeroclippers and pressurised baloons

Cirene campaign AREA


ATLAS mooring

The Cirene project

Vasco experiment
VASCO Experiment day variability

  • Statistics of multi-scale variability for a large region south of the equator

    • Diurnal to intraseasonal

    • Surface parameters

    • Top of the atmospheric boundary layer

  • Aeroclipper measurements

    • Small scale structure of the surface atmospheric and oceanic parameters in convectively suppressed or active conditions

      • Surface flux

      • SST variability (warm-layer diurnal cycle for suppressed conditions)

      • SSS variability (impact of rain events)

    • Large scale dynamics at the surface

  • Pressurized Balloon measurements

    • Large scale dynamics and thermodynamics (T,RH) around 850hPa

The Cirene project

VASCO Experiment day variability

Mean zonal wind (60-100E)



Quasi-Lagrangian Trajectories for

Pressurized Balloons and Aéroclippers

Maximum convective activity

BPs and Aeroclippers in this low-level westerly jet

The Cirene project

Vasco pilot experiment february 2005
Vasco Pilot experiment - February 2005 day variability

5 pressurised balloons and 4 Aéroclippers launched from Mahé between February 10 and February 25, 2005.

Flight until March 17 for the 1st pressurised balloons (31 days).

The Cirene project

Isopycnal pressurized balloons day variability





GPS Argos positioning and data transmission

The Cirene project

Aéroclipper day variability


Security positioning and transmission (GPS, ARGOS)

Tension (computation of height)

60 m

for V=0

Atmospheric gondola

T, RH, P, Relative Wind

Onboard computations

Science positioning and transmission (GPS, ARGOS)

Ocean gondola


The Cirene project

The cirene experiment
The Cirene experiment day variability

The Cirene project

In a few words
In a few words… day variability

  • 2 legs, start, stopover and return in Seychelles

  • Instruments deployment:

    • One ATLAS and one ADCP mooring (collaboration PMEL, to retrieve)

    • 12 Argo profilers (PROVOR)

    • 3 “dragged” surface buoys (collaboration WHOI, to retrieve)

    • XBT (every 3h) and radiosondes (two to four times a day)

  • Long stations (2 x 12 days at ~ 67°30’E, 8°S)

    • CTD with L-ADCP, PAR, transmissiometer, fluorimeter

    • 2 à 4 water samples (~5-7 levels) a day (Chlorophyll, nutrients, salinity)

    • Autonomous micro)structure profiler 0-100m (ASIP, B. Ward)

  • Continuous measurements

    • Air sea fluxes measurements (CETP-CNRM-DT INSU instrument)

    • RSMAS (U. Miami): radiometers, sky camera, radiative fluxes…

The Cirene project

Cirene first leg
Cirene, first leg day variability

Preparation: 5-8 january

Leg 1: 9-29 january

Stopover 30-31 january

Leg 2: 1-20 february

End: 21 february

The Cirene project

Cirene second leg
Cirene, second leg day variability

Preparation: 5-8 january

Leg 1: 9-29 january

Stopover 30-31 january

Leg 2: 1-20 february

End: 21 february

The Cirene project

Adcp atlas mooring
ADCP & ATLAS Mooring day variability

  • At 67°E, 8°S, where there is a significant SST and flux signal

ATLAS: long and shortwave fluxes, Tair, humidity, pressure, wind, 14 T sensors in upper 500m, 9 S sensors in upper 140m, 4-5 currentmeters

The Cirene project

The cirene measurements
The Cirene measurements day variability

(B. Ward, WHOI)

High resolution near surface profiler: diurnal cycle.

The Cirene project

The cirene measurements1
The Cirene measurements day variability

(B. Ward, WHOI)

The Cirene project

The cirene measurements2
The Cirene measurements day variability

  • WHOI drifting buoys

    • 3 balls float

    • 24 nodes thermistance chain with .5m resolution

    • Self-recording thermometers (every 5 m from 15 to 60m)

    • Deep-drogue the buoys at ~500 to 1000m to slow them down.

    • Will be deployed around

      ship at beginning of 1D

      station period & recovered

      at the end.

The Cirene project

The cirene measurements3

Refractometer (q) day variability

The Cirene measurements

  • Fluxes measurements

  • Continuous measure air-sea fluxes (momentum, heat, freshwater) with a 15% accuracy over 30minutes periods

  • Measured quantities for turbulent component of the fluxes: platform motion (6 degrees of freedom) and wind, temperature, humidity with two samplings (1 Hz=accurate low frequency sampling and 50Hz: turbulence)

  • Numerical simulations of flow around ship to correct for distortion effects

The Cirene project

Cirene measurements
Cirene measurements day variability


Optical rain


  • RSMAS (P. Minett et al.)

Radiation package

All sky camera



Weather station

The Cirene project

The cirene analyses
The Cirene analyses day variability

  • Document

    • the amplitude of the fluxes and upper ocean response

    • the amplitude of the diurnal cycle

    • The atmospheric signals…

      associated with a MJO in the Cirene region

  • Evaluate upper ocean heat and salt budget based on observations.

  • Process studies with a 1D ocean model, and with a 1D ocean-atmosphere column model.

The Cirene project

Vasco cirene complementarity
Vasco-Cirene day variabilitycomplementarity


    • Large-scale dynamical perturbations

      • Low-level jet around 850hPa and surface wind

    • Statistics of multi-scale variability of surface parameters for a (hopefully) large region

      • Diurnal to intraseasonal


    • Precise local measurements of diurnal to intraseasonal evolutions of the vertical structures for the Ocean and the Atmosphere

  • VASCO gives to CIRENE:

    • The large-scale environment of the CIRENE measurements

      • Link between CIRENE measurements and satellite/analysed fields (Spatial homogeneity, …)

    • A larger statistics for the same region and season for perturbations at the air-sea interface

      • Wind gusts, Warm-layer, Salinity, Surface fluxes, etc.

  • CIRENE gives to VASCO

    • Physical interpretation of Aeroclipper observations

      • Origin of SST and SSS variability

      • Potential impact of observed surface flux perturbation (diurnal, …) on the ocean mixed layer

    • Radiosondes for the vertical structure of the atmosphere

The Cirene project