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Title

Verification and evaluation of the aerosol microphysics parameterization in E3SM using a box model

Authors

Jian Sun (Unlicensed), Richard Easter (Unlicensed), Hui Wan Kai Zhang

Abstract

Atmospheric aerosol particles play an important role in the climate system, but the representation of aerosol processes in Earth system models still needs to be improved. The Modal Aerosol Module (MAM) used in E3SM provides a simplified but rather complete treatment of the aerosol processes. Based on assumptions on the size and composition of aerosols, the model solves different kinds of equations, including algebraic equations (e.g. for aerosol water uptake), ordinary differential equations (e.g. for trace-gas condensation), and/or partial differential equations (e.g. for sedimentation). Since many processes are involved and some of them are tightly coupled, we need to make sure that these equations are correctly formulated and accurately solved. Using the terminology from other computational sciences, we distinguish two types of testing: (1) verification, which checks whether the numerical methods and code implementation correctly solve the equations the model developer intended to formulate and solve, and (2) validation, which checks if the results reasonably represent the physical phenomena in the real world. However, testing MAM in the full E3SM is challenging, since the aerosol processes and other physical/dynamical processes have strong interactions.

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