Evaluation of MM5 Optically Thin Clouds over Europe in Fall Using ICESat Lidar Spaceborne Observations

International audienceThe description of clouds in mesoscale models has progressed significantly during recent years by improving microphysical schemes with more physical parameterizations deduced from observations. Recently, the first lidar in space, the Ice, Cloud, and Land Elevation Satellite (ICESat)/Geosciences Laser Altimeter System, has collected a valuable dataset that improves the knowledge of occurrence and macrophysical properties of clouds, and particularly high-altitude clouds, which are usually optically thin. This study evaluates the capability of the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) to reproduce optically thin clouds using the ICESat October–November 2003 dataset. Initial and boundary conditions are prescribed from NCEP products and MM5 run over the European continent with a 40-km spatial resolution. Spaceborne lidar profiles are diagnosed from model outputs and compared with the observed ones at the same location and time. One month of simulations–observations comparisons shows that the model correctly reproduces cloud structures on average, but underestimates the thinnest clouds (by 0%–20%) and overestimates less thin clouds in the upper troposphere (altitude >6 km). The total low-level water cloud amount (altitude