Study on the Characteristics and the Parameterization of Effective Radius in Stratiform Precipitation Warm Cloud of Southeastern China Based on WRF-SBM Simulation

The study on the characteristic and the parameterization of cloud droplet effective radius (r_e) is important for the optimization of warm cloud microphysical schemes in numerical models. Based on numerical simulations combined with the four aircraft observations of stratiform warm clouds in Jiangxi, China, this work investigated their microphysical properties, focusing on the evolutionary pattern and the parameterization of r_e, as well as the correlation between r_e and the number concentration (N_c) of cloud droplet and liquid water path (LWP). It is found that there is a negative correlation between r_e and N_c, and the rate of the decrease could be increased by 2–4 times with a strengthening of collision-coalescence process. What's more, the direct introduction of collision-coalescence is conducted based on the existing r_e parameterization schemes, and the results show that it can perform well in most of collision-coalescence intensities. It is also found that LWP is positively correlated with r_e when r_e is less than 12 μm, after which the relationship changes to a negative correlation due to the impact of rainfall intensity.