A global view of mixed-phase cloud distribution and ice generation in them with A-train satellite measurements

Mixed-phase clouds play an important role in the climate system, but are still poorly understood and simulated. CloudSat and CALIPSO measurements provide the first opportunity to accurately determine the mixed-phase cloud global distribution and new potentials to better characterize their properties. By combining lidar's high sensitivity to high concentration small water droplets and radar's high sensitivity to low concentration large ice particles, an algorithm is developed to reliably identify mixed-phase clouds based on CloudSat and CALIPSO measurements. For the first time, we are able to provide a global view of mixed-phase cloud distribution and their seasonal variations. Annual mean global mixed-phase cloud occurrence is ~15.3%, but regional mixed-phase cloud occurrence could as high as 60%. Mixed-phase cloud geographical and vertical distributions will be discussed in details.

By combining CloudSat and CALIPSO observations, we will also show a new global picture of ice generation in stratiform mixed-phase ice clouds. Although, there are significant dependencies of ice generation on latitudes, the general signature of temperature impacts on ice generation is consistent globally. Two distinct ice formation zones in terms of cloud top temperature (CTT), colder or warmer than -18 °C, can be identified from the observations. The contrast of ice generation in these two temperature zones indicates different dominated ice generation mechanisms among them. The impact of aerosols on ice generation in these mixed-phase clouds will also be discussed.