Evaluation of a Lagrangian advection scheme for cloud droplet diffusion growth with a maritime shallow cumulus cloud case

A Lagrangian advection scheme (LAS) for solving cloud drop diffusion growth was previously proposed (in 2020) and validated with simulations of cloud droplet spectra with a one-and-a-half dimensional (1.5D) cloud bin model for a deep convection case. The simulation results were improved with the new scheme over the original Eulerian scheme. In the present study, the authors simulated rain embryo formation with the LAS for a maritime shallow cumulus cloud case from the RICO (Rain in Cumulus over the Ocean) campaign. The model used to simulate the case was the same 1.5D cloud bin model coupled with the LAS. Comparing the model simulation results with aircraft observation data, the authors conclude that both the general microphysical properties and the detailed cloud droplet spectra are well captured. The LAS is robust and reliable for the simulation of rain formation.