Impacts of Cloud Condensation Nuclei on Deep Stratus Clouds

摘要

Simulations of a warm front associated with a deep, mixed-phase stratus cloud were performed with three different background cloud-nucleating aerosol profiles representative of clean, moderate, and polluted environments using the Regional Atmospheric Modeling System. While significant changes were seen in the cloud microphysical processes, the total precipitation reaching the surface only varied by 2% across the three simulations. This result arose from two buffering processes in the mixed-phase cloud. First, in the more polluted simulations, decreased riming of cloud water was compensated by increased vapor deposition onto ice leading to small changes in ice content and hence melting. Second, autoconversion of cloud droplets to rain was suppressed, but collection of cloud water by rain drops, which were primarily produced through melting, increased due to increased cloud water content in the more polluted simulations.