B17. P3 cloud microphysics in E3SM

Title

Implementation and performance of the P3 cloud microphysics in the E3SM atmosphere model

Authors

Kai Zhang (PNNL), Jiwen Fan* (PNNL), Jingyu Wang (PNNL), Marco Paukert (PNNL), Hui Wan (PNNL), Phil Rasch (PNNL), Xiaohong Liu (Texas A&M)

*Presenting author

Abstract

The representation of cloud microphysical processes in a global climate model has large impacts on the simulated Earth’s radiative budget and hydrological cycle. Our previous work has shown that: a) the artificial treatment of the ice-to-snow conversion process has a large impact on the net radiative balance at the top-of-the-atmosphere; b) less careful treatment of the numerical coupling of competing and compensating processes, such as the ice nucleation, ice depositional growth/sublimation, and source/sink of water vapor, can lead to inaccurate solutions. To address these problems and improve the atmosphere component of E3SM, we have implemented the single-ice-category Predicted Particle Properties (P3) scheme in the model. The scheme has been revised for use at coarser resolutions (e.g. cloud fraction treatment and consideration of subgrid variability) and to better represent the interaction between processes. We performed global nudged simulations using both P3 and MG2 (the original microphysics scheme) in E3SM and evaluated the simulated cloud, precipitation, and radiative properties. Results show that E3SM-P3 performs well in simulating macrophysical and microphysical properties of both liquid and ice clouds. We find large differences between P3 and MG2 in simulating the microphysical process rates and associated heating, which affect the simulated frequency distribution of precipitation. We further examined the reasons responsible for the improved simulation results with P3 compared to MG2. The revised P3 scheme has also been tested in at high-resolutions, which will be presented in a companion poster.