Hemispheric differences in macrophysical and microphysical properties of low-level mixed-phase clouds from observations and E3SM simulations

Abstract:

Mixed-phase clouds play an important role in the surface energy budget and regional climate in high-latitude (Arctic and Antarctic) regions. With a pristine environment in the Antarctic and a relatively polluted atmosphere in the Arctic, aerosols can affect mixed-phase cloud macrophysical and microphysical properties via modulating number concentrations of cloud droplets and ice crystals. In this study, we utilize the Department of Energy (DOE) Energy Exascale Earth System Model version 1 (E3SMv1) to understand hemispheric differences of high-latitude mixed-phase clouds and the roles of thermodynamics, dynamics, and aerosols. The A-Train satellite data (CloudSat 2B-CLDCLASS-LIDAR product), as well as long-term ground-based remote sensing measurements at the North Slope of Alaska (NSA) Utqiaġvik site and McMurdo station from the DOE Atmospheric Radiation Measurement (ARM) program are used to evaluate model simulated mixed-phase cloud differences. Low-level single-layer stratiform mixed-phase clouds that were obtained from remote sensing measurements and from high-frequency model outputs are analyzed. Our results show that, consistent with previous studies, single-layer stratiform mixed-phase clouds are ubiquitous over the high-latitude regions in both observations and model simulations. Higher frequency of occurrence is simulated by E3SMv1 in the Arctic than Antarctic, similar to observations. Simulated cloud top temperature also shows a strong hemispheric contrast, which implies the importance of thermodynamic effect on mixed-phase cloud properties. Then, hemispheric comparisons of cloud microphysical properties under constrained thermodynamics and aerosols are conducted. Moreover, the role of aerosols on single-layer stratiform mixed-phase cloud differences in two hemispheres is analyzed.