PNNL

Abstract

This study examines the vertical variation of cloud microphysical relationships and its implication on cloud microphysical processes in marine stratocumulus clouds using the data from in-situ aircraft observations during the Aerosol and Cloud Experiments in Eastern North Atlantic (ACE-ENA) field campaign. A new mixing diagram with a coordinate system based on liquid water content (L) and phase relaxation time scale is proposed to investigate what type of mixing mechanism appears dominantly. The new diagram analysis shows that the trait of inhomogeneous mixing is dominant near the cloud top, but the trait of homogeneous mixing became stronger with decreasing altitude. The relevant scale parameters also indicate a high likelihood of inhomogeneous mixing. The relationship between L and standard deviation of droplet radius (sR) clearly shows the vertical transition: the correlation between L and sR is positive at lower cloud altitudes, but it becomes negative as altitude increases. Such vertical transitions of cloud microphysical relationships are consistent with the vertical circulation mixing, modulating the cloud microphysical relationships to suggest homogeneous mixing dominance in mid-levels of these stratocumulus clouds.