Evaluation of the WDM6 scheme in the simulation of number concentrations and drop size distributions of warm-rain hydrometeors: comparisons with the observations and other schemes

Jiaxu GUO; Hengchi LEI; Di CHEN; Jiefan YANG

Evaluation of the WDM6 scheme in the simulation of number concentrations and drop size distributions of warm-rain hydrometeors: comparisons with the observations and other schemes

2019

Jiaxu GUO | Hengchi LEI | Di CHEN | Jiefan YANG

The number concentrations and drop size distributions (DSDs) of warm-rain hydrometeors play an important role in the simulation of microphysical processes. To evaluate the performance of the WDM6 scheme, which predicts the cloud number concentration (Nc) explicitly in aspects of warm-rain hydrometeors number concentrations and DSDs, the simulation of the WDM6 scheme is compared with airborne observations of a flight trial, as well as with the simulations of the Thompson scheme and Morrison scheme. Results show that the WDM6 scheme produces smaller (larger) cloud (rain) number concentrations and wider cloud DSDs compared to the observations, with the largest biases at upper levels of stratiform cloud (SC). The Thompson scheme and the Morrison scheme, both of which set the Nc as a constant, compare better to the observations than the WDM6 scheme in aspects of Nc and DSD. Sensitivity tests of the initial cloud condensation nuclei (CCN) number concentration (CCN0) of the WDM6 scheme show that a better choice of the initial CCN0 may improve the simulation of convective cloud but helps little in terms of SC. The simulation of rain number concentration and DSD is not sensitive to the CCN0 in the WDM6 scheme.

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