Ground based and ultralight-borne lidar to highlight multilayered aerosol in the frame of AMMA

The lidar system EZ LIDAR/textregister/LAUVA was operated both onboard an ultrahigh aircraft (ULA) and at the ground level (Niamey international airport, Niger, 13°31'N-2°07'E) within the framework of the first intensive field phase of the African Monsoon Multidisciplinary Analysis (AMMA; http:amma.mediasfrance.org/) which took place in the West African Sahel during the dry season in January-February 2006. This phase of AMMA was dedicated to the study of tropospheric aerosols from biomass burning and Aeolian erosion which are known to be the major aerosol sources in the West African Sahel (10-18°N) in winter. The overall objective of the campaign was to characterize the aerosol mixing between biomass burning and dust aerosols. Our system offered the only opportunity to deploy an airborne lidar during the campaign, which in turn offered a unique opportunity to document the vertical profile of the aerosol backscatter to extinction ration in a complex environment. Different aerosol layers have been observed against the altitude from both the ULA and the ground level. The lower layers were mainly composed of dust aerosol coming from the Saharan region. Significant variability has been observed in these layers due to frontal activity during the night. The upper layers were mainly associated to biomass burning aerosols coming from the Nigeria and Benin. Biomass burning aerosols were observed in the free troposphere between 2 and 5 km above the mean sea level. The presence of the biomass burning aerosols at such an altitude is likely due to the air mass ascendance associated to the monsoon flux. The existence of a complex multilayer aerosol structures against the altitude could significantly influence the radiative budget in the Sahelian area. Different aerosol vertical structures observed from lidar will be presented and their radiative impact in terms of heating rate will be discussed.