Importance of Pressure Changes in High Cloud Area Feedback Due to Global Warming

Abstract

High clouds have large impacts on the Earth's radiation balance, and a better understanding of their change in warmer climates is essential for climate projection science. Previous studies have focused on the role of large-scale circulations in high cloud change, and little attention is paid to the local processes in high clouds. Here, we show that the evolution of ice clouds in the upper troposphere due to the cloud microphysical processes is dominated by the collection, sublimation, deposition, and sedimentation using a model with an explicit cloud microphysics scheme. Furthermore, we show that these processes can be enhanced and can lead to the reduction of high clouds in warmer climates through the pressure dependencies of fall speeds of ice particles and the molecular diffusivity of water vapor. Our results highlight the importance of change of the high cloud pressure level in the high cloud area feedback.