Documentation of stratiform and cirriform region of MCSs anvils during the AMMA experiment

The African Monsoon Multidisciplinary Analyses (AMMA) - Special Observing Period (SOP) took place between 1st June and 30 September 2006 in the whole West Africa region. Of particular interest is the september month where the french Falcon 20 was loading the 95 GHz 5 beam Doppler RASTA radar, the 3 wavelength LNG lidar and a set of in-situ sensors covering the whole hydrometeor size spectrum. This aircraft can fly up to the altitude of 12.5 km. A first period (first half of september) was dedicated to the documentation of the continental MCS anvils with an aircraft based in the Niamey (Niger) airport and a second period (second half of september) to MCSs as they arrive over the Atlantic ocean with an aircraft based in the dakar (Senegal) airport.

Among other scientific objectives these two periods were devoted to:

- the documentation of stratiform and cirriform region of MCSs at different stages of their life cycle

- the quantification of the impact (in term of water, radiative and dynamical budgets) of these anvil clouds onto their environment.

- the evolution of microphysical properties as the systems move towards the ocean

- the evaluation of the CloudSat/CALIPSO level 1 and 2 products within this particular region of West Africa where operational data are usually sparse.

In this paper the observations performed in the different MCS types and life cycle steps will be illustrated as well as the evaluation of the CloudSat/CALIPSO products that will be used to extend (in space and time) the documentation performed by the the french Falcon 20. Of particular interest for this evaluation is the flight of the 22 september 2006 where the aircraft flew below the CloudSat/CALIPSO tandem within a precipitating system This flight allows a direct comparison of the radar measurements. Both the spaceborne and airborne radars exhibit strong attenuation within the anvil region well above the melting layer but still at the flight level (about 8 km in this case) the CloudSat reflectivity remains higher than the RASTA measurements. An explanation for these differences in reflectivity is that the CloudSat measurements are affected by multiple scattering as it has been already stressed in theoretical simulations. An estimation of the intensity of this effect is obtained by making use of these two measurements and is further discussed in this paper.