Boundary-layer Pressurised Balloons & Driftsondes Status of implementation on April 1 st 2006

BLPB team: –Claude Basdevant (IPSL/LMD, CNRS, Palaiseau, France) –Philippe Drobinski (IPSL/SA, CNRS, Paris, France) –Nicolas Verdier (CNES, Toulouse, France) –Philippe Coquerez (CNES, Toulouse, France) BLPB science objectives and team Main objective: The BLPB will be deployed from Cotonou between 15 June and 15 July to document the small scale dynamics of the West African monsoon flow around the monsoon onset, and address the following issues: Modulation of the monsoon by the African easterly waves. Estimation of the monsoon penetration over the continent, Quantification of the performance of NCEP/ECMWF analysis in the AMMA region, Validation of dynamical processes in research models. Funded by CNES

What are BLPB? System characteristics - Balloon diameter = 2.5 m, Helium inflated - Gondola located inside balloon - Payload 3.5 kg, total flying weight 8kg  Performances - Flight level (around 850hPa) influenced by water loading - Lifetime up to 3 weeks - Easy launching operations CNES constant volume balloons for the PBL CNES scientific payload Sensors - 3D GPS position - Air temperature - Gaz temperature - Relative humidity Sampling and data collection - 10 mn mean data sampling rate - data transmitted through Argos system Temperature and pressure sensor Humidity sensor

Strategy Launching site: Cotonou (Benin) About 20 BLPB will be released from Cotonou Sampling: One half launched on a regular time basis (every other Day), the remaining half used to increase the sampling at the time of the monsoon onset (maximum of 2-3 balloons per day) Simulated data density for launching between 15 and 25 June ( )

Status of implementation - a recce is underway this week (3-7 april) in Cottonou - a dedicated web site has been implemented by Eric Tromeur ( which will enable to monitor BLPB trajectories during the SOP.

Driftsondes team: –David Parsons (EOL/NCAR, Boulder, USA) –Philippe Drobinski (IPSL/SA, CNRS, Paris, France) –Jean-Luc Redelsperger (CNRM, Toulouse, France) –Philippe Coquerez (CNES, Toulouse, France) Driftsondes science objectives and team Main objective: The driftsondes will be launched from N’Djamena between 15 August & 15 September (flying from 15/8 to 30/9) to enhance in a significant manner the spatial radiosounding coverage of West Africa. This deployment will allow to address several scientific issues : complement the radiosounding network in regions void of measurements impact of the assimilation of the dropsonde data quantification of the performances of NWP (NCEP, ECMWF, …) on the meteorological fields (wind speed and direction, pressure, temperature and moisture) in the AMMA region. validation of research models for the understanding of the dynamical processes associated with convection and cyclogenesis. Funded by NCAR & CNES

What are BLPB? Lower stratosphere N’Djamena Gondola Dropsondes

Strategy Launching site: N’Djamena About 8-10 Gondolas will be released carrying 50 dropsondes Flight level: hPa Sampling: the gondolas will release the dropsondes, either at regular times or on demand. The current plan is to have dropsonde releases at synoptic hours (0000 and 1200 UTC), in addition to dropping on demand based on targeting needs for hurricanes, developing tropical cyclones and AMMA convective systems. The lifetime of the gondolas being on the order of 15 days, typical operations will imply that approximately 30 dropsondes will be released for twice daily soundings and approximately 20 will be available for ‘responsive’ launches.

Status of implementation - Technical aspects: NCAR managed to reduce the weight of their dropsondes and the last tests of the new CNES pressurized balloons launched from Kiruna (in february) were successful. - Administrative aspects: end of january the authorizations for launching and flying over were asked by CNES to the all concerned countries ambassies. CNES also asked for authorization to the French military services for assistance in the deployment of the stratosferic driftsonde system (SDS) from N'Djamena. The status for all these actions is "pending". - Decision making center:  Niamey for launching Gondolas  Toulouse for releasing dropsondes