An airborne Raman lidar to sample horizontal meteorological fields in the framework of MAESTRO

The Airborne Weather and Aerosol Lidar (A-WALI) is the first airborne meteorological lidar using Raman technology to measure the horizontal fields of water vapour, temperature, clouds and aerosols, as key weather and climate parameters (https://metclim-lidars.aeris-data.fr/). Based on lidar technologies tested in WALI (Totems et al., 2021; Chazette et al., 2014)) and ALiAS (Chazette et al., 2020), it was developed to meet the scientific objectives of ERC project MAESTRO (Mesoscale Organisation of Tropical Convection, https://maestro.aeris-data.fr). This experiment was motivated by the scarcity of observations of convective clouds organisation and their environment over the oceans, whereas this spatial organisation of mesoscale clouds, i.e. the tendency of convective clouds to aggregate and form clusters of varying horizontal and vertical extent, plays an important role in climate and meteorology. One of the objectives of the MAESTRO airborne campaign was therefore to sample the horizontal distribution of meteorological temperature and humidity fields, as well as the spatial distribution of aerosols and clouds. A-WALI was flown on board the ATR-42 aircraft of the SAFIRE unit (https://www.safire.fr/), departing from Sal in Cape Verde. The experiment, which took place between 10 August and 10 September 2024, was part of the international campaign ORCESTRA (Organised Convection Experiments in the Tropical Atlantic) supported by the World Climate Research Programme.

We will give examples of the measurements made by A-WALI and estimates of the associated uncertainties. We will discuss the calibration approach, the lidar sampling capabilities and limitations. Depending on the geophysical parameter under consideration, we will show at which spatial scales the lidar measurement provides relevant information and what its range can be.