Investigating the Effect of Soot Emissions on Precipitation over Western CONUS Using WRF-Chem

Monday, 15 December 2014
Hsien-Liang Rose Tseng1, Kuo-Nan Liou1,2, Yu Gu1,2, Longtao Wu2,3 and Robert G Fovell1, (1)Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, United States, (2)Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, CA, United States, (3)Jet Propulsion Lab-MLS, Pasadena, CA, United States
The current Exceptional Drought (US Drought Monitor) over the Western Continental United States (CONUS) warrants an in-depth investigation of possible causes of decreased precipitation. Soot, a mixture of black carbon and organic carbon, can increase in its hygroscopicity by two-fold (at relative humidity of 80%) when coated with sulfuric acid, rendering smaller, although quantitatively more, cloud particles. This has the potential to exacerbate the aridity in the western states. In this study, we examined the role of soot and its possible effect on reducing precipitation west of and over the Rocky Mountains from an online and coupled meteorological and chemical perspective. In particular, we utilized the Weather Research and Forecasting-Chemistry (WRF-Chem) model at the horizontal resolution of 30 km, employing the Fu-Liou-Gu plane-parallel radiation scheme and a three dimensional parametrization over mountainous areas to account for direct and indirect feedback of soot and cloud particles, including ice crystals, to understand precipitation patterns based on simulation results. Identifying factors that can mediate drought severity will improve hydrological prediction, and subsequent resource usage and allocation.