Investigating the nondeterministic processes of boundary-layer clouds using ARM observations and high-resolution simulations

Description

Cloud parameterizations are developed based on the parameterizability assumption: that is, the sub-grid-scale (SGS) cloud processes can be solely determined in terms of the large-scale properties resolved by weather and climate models. In this framework, the effects of some important internal cloud processes, such as precipitation and cloud mesoscale organizations, are either neglected or simplified into a conceptual cloud model. Previous studies show that some important cloud processes and organizations are not fully controlled by large-scale forcings. The existence of the nondeterministic cloud processes indicates the limit of deterministic parameterizability of clouds. In this study, using the multiple-scale Weather Research and Forecasting (WRF) simulation featuring a large-eddy simulation in the hindcasting mode, we investigated the nondeterministic effect of precipitation on the parameterization of precipitating shallow cumuli and stratocumulus clouds based on the cloudy cases observed at the ARM sites. Two sets of simulations with full microphysics and with the precipitation turned off are executed to illustrate how the precipitation affects the deterministic parameterizability of the vertical fluxes induced by clouds.