Microphysical Impacts on Convection Applying Novel Modeling Methodology in Weather Research and Forecasting Model: Comparison between Bulk and Bin Microphysics

Evaluation of the impact of microphysics on convection are challenging. Grabowski (2014) recommended a new methodology to assess effects of different microphysical properties on dynamics and macroscopic variables in shallow convection. The main idea of this novel approach is to have two sets of thermodynamic and microphysics variables (temperature, water vapor, and microphysical particle mixing ratios / and number concentrations). While the elements of first set are evaluated by solution of partial differential equation system describing the interaction between microphysics, thermodynamics and dynamics (DRIVER), the element of second set are calculated by a different microphysics using the dynamics has been given by the DRIVER, that is there is no feedback due to microphysics (PIGGYBACKER). Previous studies used a simplified serial version of the 3D nonhydrostatic anelastic Eulerian–semi-Lagrangian (EULAG) model (http://www.mmm.ucar.edu/eulag/).

In this current research this new method has been implemented into a widely used numerical weather prediction model (WRF). The sensitivity of the precipitation formation in an idealized squall line case on the microphysics scheme (bulk versus bin) has been studied by piggybacking methodology. The 3D simulations are performed by the following way: (1) bulk scheme drives the model and bin scheme piggybacks, (2) bin scheme drives the model and the same bulk scheme piggybacks the flow. The results of the WRF-based bin and bulk microphysics piggybacking simulations will be presented and discussed at the conference for the first time.