Precipitating convection in the tropics is associated with instability extending throughout the atmospheric column, deep latent heating profiles that maximize in the upper troposphere and a vertical ascent that can often overshoot through the tropopause. These key properties are thought to be crucial for maintaining a number of atmospheric phenomena. These include convectively-coupled wave propagation, moisture transport into the stratosphere, wave driving of the Quasi Biennial Oscillation (QBO), and thermodynamic structure in the mean tropical climate.

By several measures, the vertical extent of deep convection from the existing Zhang-McFarlane (ZM) convection scheme in the Community Earth System Model (CESM) Community Atmosphere Model (CAM) is too shallow in the tropics. This issue became especially evident following the introduction of measures to increase moisture sensitivity in previous model versions CAM4 and CAM6, and more recently, to reduce parameterization sensitivity to increased vertical resolution in CAM7. While these past measures have led to some clear positive impacts, such as an improved MJO, delayed precipitation diurnal cycle and better tropospheric humidity distributions, it is clear that both for individual events and in the mean as a whole, ZM convection is terminating too low in altitude.

In this talk we will show results from efforts to increase convective depth through modifications of the existing ZM scheme. The proposed approach considers the convective parcel vertical extent from a total energy perspective and not solely a potential energy/buoyancy perspective. Fundamentally, it is a simplified vertical velocity equation approximation that allows the kinetic energy of convective parcels to be used to determine convective vertical extent and integrated buoyancy. This approach allows ascending test parcels in ZM to overcome weak negative buoyancy regions and occasionally achieve overshoot beyond the existing parcel zero buoyancy termination level. This talk focuses on experiments with the most recent development versions of CAM7 and examines the sensitivity to choices of initial parcel energy and the efficiency of potential energy to kinetic energy conversations.