Implementation of a Linear-Wave Harness in the Common Community Physics Package Single Column Model: Sensitivity to Parameterized Convective Downdrafts, Rain Re-Evaporation, and Cloud Detrainment

A “linear-wave-harness” configuration is implemented in the Common Community Physics Package Single-Column Model (CCPP SCM) for investigating how assumptions about convection parameterization modulate the simulation of convectively coupled Kelvin waves (CCKWs). The linear-wave-harness is constructed by coupling the set of equations that describe large-scale, two-dimensional gravity waves with the CCPP SCM configured in a state of radiative-convective-dynamical equilibrium. The assumptions tested include those pertaining to the strength and starting level of deep convective downdrafts, the strength of re-evaporation of rain, and the level at which cloud condensate starts to detrain in the Simplified Arakawa-Schubert (SAS) convection scheme. We have found that different combinations of these four parameters lead to different vertical distributions of cloud condensate and convective heating, both of which affect the instability of CCKWs. In addition, enhancing either one or both of the factors affecting deep convective downdrafts and the re-evaporation of rain is found to reduce a longstanding dry bias in the lower tropical troposphere.