Aerosol Association with Severe Weather in Oklahoma

Aerosol particles may serve as cloud condensation nuclei (CCN) and therefore play an important role in modulating cloud microphysics. Clouds forming in regions of high CCN concentration have been observed to contain higher concentration of small cloud droplets, suppressing precipitation and delaying the warm-rain process. This increases cloud water concentration, leading to higher liquid droplet and ice crystal number concentration, which enhances latent heat release and helps invigorate convection. The purpose of this study is to determine the impacts of biomass burning aerosols on convective storms over the Southern Great Plains, particularly in Oklahoma. A new technique to identify days with a high concentration of biomass burning aerosols will be developed by using organic carbon, potassium, zinc, and bromine as the predominant tracers. An eleven-year climatology (2002-2012) for the biomass tracers will be produced to identify days on which biomass burning particles are present and an average concentration of these tracers will be obtained from three different sites in Oklahoma: Ellis, Wichita Mountains, and Stillwater. Once prevalence of biomass burning particles is identified for each day using tracer data, days will be classified into high, medium, and low biomass burning particle concentration with the lowest 30% of values considered low concentration days, the middle 40% considered medium concentration days, and the highest 30% considered high concentration days. Only the March through June time period will be used since this is climatologically the convective season on the Southern Great Plains. Days with severe and non-severe thunderstorms will be identified and used as case study days to identify impacts of aerosols on deep convection in this region. Storm reports and polarimetric radar data will be utilized. For each case study day, synoptic and surface features responsible for initiating thunderstorms will be identified. The results of this study should provide clearer insight into what synoptic regimes are most common under high, medium, and low biomass burning situations and whether severe weather/storm outcome is more affected in some synoptic regimes than others.