EAGER: Development of a Bulk-Emulating Microphysics Scheme

University Of California-Davis, Davis CA

Investigators

Abstract

Numerical weather and climate models use cloud microphysical schemes to represent how a large collection of cloud particles grow, interact, and decay. Explicitly modeling the full characteristics of a cloud, such as the distribution of different particle sizes, is not computationally feasible for most purposes, so researchers have devised schemes that can accurately represent certain quantities that are important for the models. However, there are some processes that depend greatly on aspects such as the particle size distribution, so having an improved understanding of the differences between the two approaches would be useful to identify problems. This work will create a cloud scheme that is based upon explicit cloud modeling but is comparable to the less computationally advanced schemes so that direct comparisons can be conducted. The main societal impact would be the downstream effect on weather and climate models. The project also provides training for a graduate student. This project aims to develop a bulk-emulating microphysics scheme. There are two common classes of microphysics schemes, the bin scheme where the particle size distribution is explicitly predicted, and the bulk scheme where 1-3 integral quantities of the particle size distribution are predicted. Bin schemes are computationally expensive and not feasible for use in global climate models. However, it has been recently suggested by the scientific community that bulk schemes are incapable of properly representing aerosol-cloud interactions. This project will develop a tool and method for testing the conceptual and numerical limitations of bulk microphysics schemes with an end goal of informing the community how new schemes should be designed in the future. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.