Characterizing convective sensitivity to the large-scale: What and how do parcels entrain?

Abstract

Convective parameterization has tended to rely on easily definable quantities such as Convectively Available Potential Energy (CAPE) of an undilute parcel, in order to determine depth and strength of convection. However, such an approach largely confines large-scale sensitivity to the boundary layer and minimizes any influence of free tropospheric humidity, or the lack thereof.

By considering the possibility of numerous (more than 1!) successively entraining parcels it is possible to better characterize convective activity and the constraints provided by the free troposphere. Climatological analyses of soundings from the Gulf of Mexico are used to characterize a mid-summer rainfall minimum; and adjustments to the convective mass-flux parametrization of SCAM (The NCAR Single Column CAM) provide obvious improvements in the occurrence of convection over the ARM site in Oklahoma.