Tracer Studies of Transport and Transformation in Cumuli

摘要

Airborne measurements near Champaign, Illinois and Milwaukee, Wisconsin were made during the summers of 1990 and 1992. Measurements of the aerosol size distribution, wind, turbulence, cloud microphysics and trace gas measurements were collected from 31 research flights. The main objectives was to document transport and transformation by cumuli, but data on out of cloud transformation processes were also collected. The results from the entrainment experiments suggested that, during the early stages of entrainment the tracer remained mostly out the cloud and was carried alongside the upper cloud regions by the circulation present there. Later, the tracer mixed into the main portion of the turrents and rapidly diluted. The observations are consistent with the hypothesis that entrainment occurs through a vortex-like circulation that brings air from just above the rising cloud top into the central region of the cloud.