This project is implementing an advanced scheme to represent hydrometeors in the Weather Research and Forecasting (WRF) model. In this new scheme, populations in each hydrometeor class are represented in a number of equally sized, interacting groupings, thus allowing the number distribution of hydrometeor sizes in a volume to develop according to physical principles. WRF is a prominent effort to develop a mesoscale model for research as well as operational use. WRF promises to be the premier mesoscale model for both uses in the near future. This and other mesoscale models have been shown to be sensitive to how microphysical processes are represented, so improvements in such representation can be of substantial benefit to the community of WRF users. Preliminary studies have shown that it is possible and, in some cases, practical (with present computing capabilities) to include this advanced representation of hydrometeor populations in such a model. Such a representation will make it possible to represent microphysical processes in much more realistic ways and in greater detail than with present schemes, which parameterize microphysical processes and therefore involve significant simplification of the physical processes that occur in clouds. This project is taking the necessary preliminary steps toward this goal by implementing the spectral representation of hydrometeors in the WRF model and then using this code to test its performance in some idealized cases that are being used for standard testing of WRF microphysical schemes.
The primary broader impact of this project is that, if successful, this spectral representation of microphysical processes can be of widespread benefit to other investigators who may use the WRF model in their research.
