An observational comparison of microphysical representations in WRF

This research investigates shortcomings of the microphysics schemes used in the numerical weather prediction in regions of complex terrain. The IMPROVE-2 field campaign provides a high-resolution dataset, co-located with Oregon's Cascade Mountains, that is suitable for testing the parameterizations used in mesoscale models. The 13-14 December IMPROVE-2 event was selected due to prior study using MM5 and Reisner-II microphysics and the quality of observational data assets throughout the vigorous frontal passage. The current study utilizes three-dimensional Weather Research and Forecasting (WRF) model simulations from the 13-14 December IMPROVE-II case, building upon the prior work to include analysis of forecasts using the latest microphysics schemes: (1) Woods' (2006) modification of the Reisner-Thompson scheme in order to predict the habit composition of the snow field, including seven prognostic equations, each of which predicts the mixing ratio of snow of a particular crystal type, (2) the Thompson scheme—the only scheme that uses both ice water content and temperature to assume snow size distributions, which it represents as a sum of exponential and gamma distributions (Thompson et al., 2006), and (3) NCAR's WSM 6 Class scheme with graupel.

Model output for each microphysics scheme will be compared against aircraft data, including crystal data in regions of orographically forced ascent (from the 2D-C probe), cloud liquid water (from the King probe), and dual-doppler derived reflectivity and wind fields. Additional consideration of microphysics schemes in the context of recent numerical insights will also be presented.