Entrainment and Tropical Cumulus Congestus Cloud Growth
Poster PDF
Authors
Michael Jensen — Brookhaven National Laboratory
Tami Fairless — Pacific Northwest National Laboratory
Katherine Towey — The Graduate Center, City University of New York
Description
We use observations from the ARM Climate Research Facility sites in the tropical Western Pacific and tropical AMF deployments to revisit the growth of cumulus congestus clouds and the factors that control their lifecycle (Jensen et al. 2006). We revisit the relative importance of freezing layer stability and mid-tropospheric dry layers in limiting the growth of terminal cumulus congestus considering only “terminal” congestus clouds (Luo et al. 2009). We use radar-observed Doppler velocities to determine the state (“terminal” vs. “transient”) of cloud growth. We then investigate how cloud parcel buoyancy and bulk entrainment of individual clouds are impacted by environmental conditions. Preliminary results for analysis of the full observational record at Nauru support the original conclusions from Jensen et al. (2006) that bulk entrainment rate decreases as a function of congestus cloud-top height and the mid-level humidity is the critical factor limiting congestus cloud growth.
