Evaluation of the Simulation of Mixed Phase Cloud with Three New Cloud Physical Schemes in Community Integrated Earth System Model (CIESM)

Abstract:

The cloud composed of both liquid and ice phase water is called mixed phase cloud and occurs extensively in all seasons and in mid-high latitudes (Choi et al., 2010). Cloud with different phases has different impact on radiation due to their disparity of optical properties (Matus & L'Ecuyer, 2017). The simulation of global mixed phase cloud still has a large variation among multiple GCMs (McCoy et al., 2016) and noticeable bias in comparison with satellite measurement (Guo et al., 2020). In this study, we evaluate the mixed phase cloud in CIESM(Lin et al., 2020) by utilizing the satellite simulator COSP1.4. The three new cloud physical schemes implemented in CIESM include a diagnostic Gaussian PDF cloud macrophysical scheme (GA) (Qin et al., 2018), a single ice cloud microphysical scheme (SI) (Zhao et al., 2017) and a semi-analytical cloud droplet spectral dispersion scheme (DI) (Liu & Li, 2015). We conduct nine sensitive experiments with different combination of the three new cloud schemes, and analyze the performance of simulated mixed phase cloud by comparing to satellite observational data. The SI scheme significantly improves the simulated fraction of mixed phase cloud due to the prognostic partition of cloud water and cloud ice, while the GA and SI schemes have relatively weak improvements. The SI+GA experiment shows the best agreement with satellite observation among the nine experiments. The three new cloud schemes influence the simulated mixed phase cloud by exerting different impacts on cloud physical processes. The accretion of cloud water by cloud ice, self-collision and shallow convective detrainment are evidently modified by SI scheme. The condensation and accretion of cloud water by cloud ice play an important role in GA scheme and the auto-conversion process is strongly altered with DI scheme.