The “CIRENE” campaign Jan-Feb 2007

1. The “CIRENE” campaign Jan-Feb 2007 P.I. J. Vialard jv@lodyc.jussieu.fr The Cirene project

2. 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

3. 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

4. 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

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

6. SST response to the MJO • 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

7. 1D Modelling of the role of diurnal cycle in COARE 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

8. Scientific questions ? 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

9. Two components • 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

10. Two components VASCO aeroclippers and pressurised baloons Cirene campaign AREA Seychelles ATLAS mooring The Cirene project

11. VASCO Experiment • 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

12. VASCO Experiment Mean zonal wind (60-100E) South North Quasi-Lagrangian Trajectories for Pressurized Balloons and Aéroclippers Maximum convective activity BPs and Aeroclippers in this low-level westerly jet The Cirene project

13. Vasco Pilot experiment - February 2005 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

14. Isopycnal pressurized balloons 2.5m T P Q GPS Argos positioning and data transmission The Cirene project

15. Aéroclipper 6m 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 SST SSS Speed The Cirene project

16. The Cirene experiment The Cirene project

17. In a few words… • 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

18. Cirene, first leg Preparation: 5-8 january Leg 1: 9-29 january Stopover 30-31 january Leg 2: 1-20 february End: 21 february The Cirene project

19. Cirene, second leg Preparation: 5-8 january Leg 1: 9-29 january Stopover 30-31 january Leg 2: 1-20 february End: 21 february The Cirene project

20. ADCP & ATLAS Mooring • 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

21. The Cirene measurements (B. Ward, WHOI) High resolution near surface profiler: diurnal cycle. The Cirene project

22. The Cirene measurements (B. Ward, WHOI) The Cirene project

23. The Cirene measurements • 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

24. Refractometer (q) 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

25. Cirene measurements M-AERI Optical rain gauge • RSMAS (P. Minett et al.) Radiation package All sky camera Microwave radiometer Weather station The Cirene project

26. The Cirene analyses • 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

27. Vasco-Cirene complementarity • VASCO • 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 • CIRENE • 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