Use of an explicit model of the microphysics of precipitating stratiform cloud to test a bulk microphysics scheme

An explicit microphysical model is used to study the development of nimbostratus cloud. The model contains a simple representation of embedded convection. The results show that secondary ice processes can be important in determining the ice and liquid-water contents of the cloud, especially when embedded convection is switched on. The results are used to test the bulk microphysical parametrization that is used in a state-of-the-art climate model, by running the bulk scheme within the same dynamical framework as the explicit scheme. Compared with the explicit scheme, the bulk scheme overestimates the ice and underestimates the liquid-water content compared with the explicit scheme. To parametrize the secondary ice processes effectively, the bulk scheme will require representation of small ice crystals.