Parameterizations

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Atmosphere Model Working Group scientists both at NCAR and within the broader community are constantly seeking ways to improve the representation of physical and/or unresolved processes within the Community Atmosphere Model (CAM). Below we describe 3 major ongoing efforts to develop or improve parameterizations in CAM. However, other important efforts by individual scientists or smaller teams of scientists are also underway. We welcome input from community members on their current parameterization related research.

Momentum transport in CLUBB

This project proposes to parameterize momentum transport by prognosing subgrid momentum fluxes directly using the Cloud-Layers Unified by Binormals framework (CLUBB; Golaz et al. 2002). This approach is quite different from conventional approaches, but it adheres more closely to the governing dynamical equations, and hence is more flexible and general.

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The Eddy-Diffusivity/Mass-Flux

The goal of this project is to reduce key biases related to boundary layer clouds and deep convection in the latest version of CAM, by implementing, and evaluating, a new unified boundary layer and convection parameterization based on the multi-plume Eddy-Diffusivity/Mass-Flux approach (Siebesma et al., 2007).

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Parameterizing Unified Microphysics Across Scales

The Parameterization of Unified Microphysics Across Scales (PUMAS) is the continued evolution of the MG microphysics scheme. The current version in CAM (MG3) is a 2 moment (Mass, Number) and 5 class (Liquid, Ice, Rain, Snow, Graupel) bulk microphysics scheme.

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Parameterization of subgrid heterogeneity

This project aims to communicate subgrid variability in the atmosphere to other model components, and how to communicate subgrid variability at the surface back to the atmosphere

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Deterministic Immersion Freezing Ice Nucleation

This project aims to parameterize the ice nucleation process for cloud droplets containing ice nucleating particles based on empirical observations. This new parameterization is targeted to replace the classical ice nucleation theory approach currently used in CAM6.

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Update radiation code to RRTMGP

This project proposes a transition from RRTMG to RTE-RRTMGP for radiation. The goal is to provide a more scalable, modular code base and to make it easier to adapt radiation to application.

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