Jiwen Fan — Pacific Northwest National Laboratory
L. Ruby Leung — Pacific Northwest National Laboratory
Daniel Rosenfeld — The Hebrew University of Jerusalem
Qian Chen — Nanjing University of Information Science and Technology
Zhanqing Li — University of Maryland
Jinqiang Zhang — University of Maryland
Hongru Yan — University of Maryland
Category
CAPI Deep Convective Clouds
Description
Deep convective clouds (DCCs) play a crucial role in the general circulation, energy, and hydrological cycle of our climate system. Aerosol particles can influence DCCs by altering cloud properties, precipitation regimes, and radiation balance. Previous studies reported both invigoration and suppression of DCCs by aerosols, but few were concerned with the whole life cycle of DCC. By conducting multiple month-long cloud-resolving simulations with spectral-bin cloud microphysics that capture the observed macro- and micro-physical properties of summer convective clouds and precipitation in the tropics and mid-latitudes, this study provides a comprehensive view of how aerosols affect cloud cover, cloud top height (CTH), and radiative forcing. We found that, while the widely accepted theory of DCC invigoration due to aerosol’s thermodynamic effect (additional latent heat release from freezing of greater amount of cloud water) may work during the growing stage, it is microphysical effect influenced by aerosols that drives the dramatic increase in cloud cover, CTH, and cloud thickness at the mature and dissipation stages by inducing larger amount of smaller but longer-lasting ice particles in the stratiform/anvils of DCCs, even when thermodynamic invigoration of convection is absent. The thermodynamic invigoration effect contributes up to ~27% of total increase in cloud cover. The overall aerosol indirect effect is an atmospheric radiative warming (3 to 5 W m-2) and a surface cooling (−5 to −8 W m-2). The modeling findings are confirmed by the analyses of ample measurements made at three sites of distinctly different environments.
Lead PI
L. Ruby Leung — Pacific Northwest National Laboratory
