10.1    Can coupled fire-atmosphere models predict smoke-induced inversions from wildfires?

Mallia, Derek V., Adam K. Kochanski, Department of Atmospheric Sciences, University of Utah, Salt Lake City, Jan Mandel, Department of Mathematical and Statistical Sciences, University of Colorado, and Tim Brown, Desert Research Institute

During the summer of 2015, a number of large wildfires burned across northern California in areas of localized topographic relief. Persistent valley smoke hindered fire-fighting efforts, delayed helicopter operations, and exposed communities to hazardous air quality. It was hypothesized that smoke from wildfires reduced the amount of incoming solar radiation reaching the ground, which resulted in near-surface cooling, while smoke aerosols resulted in warming aloft. As a result of increased inversion-like conditions, smoke from wildfires became trapped within mountain valleys adjacent to active wildfires. In this study, wildfire smoke-induced inversion episodes across northern California were examined using a modeling framework that couples an atmospheric, chemical, and fire spread model (WRF-SFIRE-CHEM). Modeling results examined in this study indicate that wildfire smoke reduced incoming solar radiation during the afternoon, which lead to local surface cooling by up to 3C, which agrees with cooling observed at nearby surface stations. A positive feedback associated with the presence of smoke was observed, where local smoke-induced inversions inhibited the growth of the planetary boundary layer, and reduce surface winds, which resulted in smoke accumulation in valleys adjacent to wildfires. This work suggests that the inclusion of fire-smoke-atmosphere feedbacks in a coupled modeling framework such as WRF-SFIRE-CHEM can forecast the dispersion of wildfire smoke, its radiative feedbacks, and poor air quality events associated with wildfires.