Direct calculation of entrainment and detrainment rates is used to evaluate the Kain-Fritsch convective parameterization scheme in shallow and deep convection. From the large-eddy simulation results, it is found that the Kain-Fritsch estimates of entrainment and detrainment in shallow convection do not accurately reflect the mixing dynamics observed in the high-resolution model. Moreover, the fractional entrainment and detrainment rates are found to be solely dependent on the cloud core buoyancy and vertical velocity, contradicting the assumptions made in the traditional parameterization schemes. A number of parameterizations for fractional entrainment and detrainment rates are presented, as the dynamics that govern the mixing processes appear to be largely different in shallow and deep convection. Nevertheless, the suggested parameterizations can accurately represent turbulent mixing processes in shallow and deep cumulus clouds.
Improving Kain-Fritsch Convective Parameterization Using Direct Calculations of Entrainment and Detrainment in Shallow and Deep Convection
August 2014