OP-I1.3 Wildfire impact on severe convective storms

Abstract

Wildfire is a type of climate extremes, and its frequency, burning season and area have been increasing globally over the past decades. Besides serving as a globally important source of aerosol particles that could impact cloud, precipitation and radiation,  biomass burning can heat the environment significantly and perturb the environmental thermodynamics when the burned area is large. However, this impact on environment thermodynamics and the subsequent influence on severe convective storms has never been investigated. In this study, we developed a new model capability based on Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) by considering heat fluxes from wildfires in the atmosphere. We evaluate the model development with several wildfire events in simulating the thermodynamics observed from soundings. Particularly, we conduct model simulations for the Mallard fire pyrocumulonimbus event occurring in Texas and Oklahoma on May 11-12, 2018, and explore how the large fire that began in early May in the region modify the thermodynamics of atmosphere and aerosol properties and how these changes affect the initiation and development of the pyrocumulonimbus clouds, which produce quite amount of lightning and some hailstones. We evaluate our model simulations with observations from radar, sounding, satellite measurements of lightning, and severe weather reports from NOAA Storm Prediction Center (SPC). With the thermodynamic effect of fire plumes considered, the initiation and intensity of the convection as well as the lightning and maximum hail size are much better simulated. This suggests the importance of accounting for impact of wildfire to environment thermodynamics in severe storm simulation and prediction.