The variability of the microphysical and radiative properties of tropical ice clouds from CloudSat-CALIPSO and ground-based ARM radar-lidar observations

The importance of clouds on the evolution of climate through their direct effect on the earth radiation budget and water cycle is well recognized. However, despite significant improvements brought to the representation of clouds in models, clouds still remain by far the largest source of spread among future climate projections produced by climate models. Among the different clouds forming in the troposphere and preferential regions of high cloud occurrence, tropical ice clouds are of particular importance, owing to their extensive horizontal and vertical coverage, and their long life time. In the present study we use CloudSat and CALIPSO data, Darwin ARM radar-lidar observations, and different indices characterizing the large-scale environment for the period 2006-2009 to better understand the impact of ice clouds on weather and climate by characterizing their statistical microphysical and radiative properties and the variability of these properties as a function of many environmental factors, such as the large-scale forcing (ENSO modulation, MJO episodes, cloud regime, large-scale atmospheric regime, etc …). This characterization is also a powerful tool to better understand why models fail to represent ice clouds accurately and for which large-scale environment, which will be the next step of this study.