Influence of bulk microphysics schemes upon Weather Research and Forecasting (WRF) version 3.6.1 nor'easter simulations

Abstract

Abstract. This study evaluated the impact of five singleor double-moment bulk microphysics schemes (BMPSs) on Weather Research and Forecasting model (WRF) simulations of seven intense wintertime cyclones impacting the midAtlantic United States; 5-day long WRF simulations were initialized roughly 24 h prior to the onset of coastal cyclogenesis off the North Carolina coastline. In all, 35 model simulations (five BMPSs and seven cases) were run and their associated microphysics-related storm properties (hydrometer mixing ratios, precipitation, and radar reflectivity) were evaluated against model analysis and available gridded radar and ground-based precipitation products. Inter-BMPS comparisons of column-integrated mixing ratios and mixing ratio profiles reveal little variability in non-frozen hydrometeor species due to their shared programming heritage, yet their assumptions concerning snow and graupel intercepts, ice supersaturation, snow and graupel density maps, and terminal velocities led to considerable variability in both simulated frozen hydrometeor species and radar reflectivity. WRF-simulated precipitation fields exhibit minor spatiotemporal variability amongst BMPSs, yet their spatial extent is largely conserved. Compared to ground-based precipitation data, WRF simulations demonstrate low-to-moderate (0.217-0.414) threat scores and a rainfall distribution shifted toward higher values. Finally, an analysis of WRF and gridded radar reflectivity data via contoured frequency with altitude diagrams (CFADs) reveals notable variability amongst BMPSs, where better performing schemes favored lower graupel mixing ratios and better underlying aggregation assumptions.

Microphysics of Snowfall Over Coastal East Antarctica Simulated by Polar WRF and Observed by Radar

“…Ground‐based radar products are valuable data for evaluating and validating the representation of microphysical processes in atmospheric models (e.g., Gerber et al, , Min et al, , Nicholls et al, ). In the austral summer 2015–2016, the intensive Antarctic Precipitation, Remote Sensing from Surface and Space (APRES3) campaign of precipitation observation—including the deployment of a polarimetric radar and of a Multi‐Angle Snowflake Camera (hereafter MASC)—took place at Dumont d'Urville (DDU) station, Adélie Land, East Antarctica.…”

Explicitly Resolving Lightning and Electrification Processes From the 10–12 April 2019 Thundersnow Outbreak

“…This study used both the 3‐D and isothermal reflectivity data for validating NU‐WRF‐ELEC simulation output and to provide context to the processes associated with observed thundersnow initiation. More specifically, simulated and observed 3‐D reflectivity structures were examined via contour frequency by altitude diagram (CFAD) scores (CS h ; Nicholls et al., 2017) which compare the probability density functions (PDFs) of the observed and simulated reflectivity at individual heights: $$${\mathrm{C}\mathrm{S}}_{\mathrm{h}}=1-\frac{\sum {\vert PD{F}_{m}-PD{F}_{o}\vert }_{h}}{200}$$$ …”

“…The CS h value ranges from 0 (no agreement) to 1 (complete agreement) between NU‐WRF‐ELEC and MRMS reflectivity PDFs at a specific height. One benefit of using CS h is that it is insensitive to any spatiotemporal errors with the model compared to observations (Lang et al., 2014; Nicholls et al., 2017; Yuter & Houze, 1995).…”