A shallow-deep unified stochastic mass flux cumulus parameterization in the single column Community Earth System Model (CESM)

We introduce some modifications to the Zhang and McFarlane (1995) cumulus parametrization by essentially changing the way the plume ensemble mass flux is computed in order to produce a fully stochastic plume ensemble cumulus scheme. We combine a purely stochastic counting process, of the number of plumes that are launched at a given time and location with the stochastic multicloud lattice model of Khouider et al. 2010. The counting process combines the approach used by Cohen and Craig 2006 of assuming a Poisson process for the number of plumes and, the approach of Gentine et al. 2013 of prescribing a distribution of plume detrainment levels, applied to various cloud types as predicted by the stochastic multicloud model. One important modification made here for the multicloud model however, is to consider shallow, congestus, and deep cloud types instead of congestus, deep, and stratiform, as done in Khouider et al. (2010) and in Khouider (2013). However, the mathematical derivations in both Khouider et al. (2010) and Khouider (2013) (without and with local interactions, respectively) apply.

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