WRF-Chem simulation of a Southwest United States dust-on-snow episode

TitleWRF-Chem simulation of a Southwest United States dust-on-snow episode
Publication TypeConference Proceedings
Year of Publication2022
AuthorsDhital S, Webb N, Kaplan ML, Nauman TW, Duni D, LeGrand S, Letcher TW, S. Skiles MK, Naple P, Chaney NW, Cai J
Conference NameAmerican Geophysical Union Fall Meeting
Date Published12- 9 to14- 2022
Conference LocationChicago, IL
ARIS Log Number396729
Keywordsdust emission, dust-on-snow, episode, simulation, snowpack, Southwest United States, Upper Colorado River Basin, WRF-Chem

Every year in spring (March-May) a large amount of dust is mobilized across the southwest United States and transported to the mountains that make up the Upper Colorado River Basin. The dust degrades air quality and influences snow hydrology when deposited on mountain snowpack. During 8-17 April 2013, three strong dust events transported a large amount of dust from the southwest drylands to the San Juan Mountains in Colorado where it subsequently accelerated snow melt and runoff. Despite the relevance of these repeated southwest dryland to mountain dust-on-snow episodes to regional hydrology, simulating dust emission and transport to the mountain snowpack accurately remains a challenge. Accurate prediction of dust-on-snow episodes at the scales that impact snowmelt rates would support water resource management in the southwest where communities and agriculture face critical water shortages, compounded by a regional megadrought. In this study, we analyzed the 15-17 April 2013 dust-on-snow event. The objectives of our analysis were to examine: 1) the meteorological setup that organized the dust episode; and 2) the capability of the Weather Research and Forecasting model with Chemistry (WRF-Chem) to simulate the dust episode. To simulate dust emission, we incorporate a satellite albedo-based drag partition parameterization into the Air Force Weather Agency (AFWA) dust emission module to improve the representation of wind stress on the erodible surface. We used reanalysis datasets, satellite and surface observations, upper-air observations, and high-resolution WRF-Chem simulations with horizontal resolutions of 18 km down to 2 km. Our analysis revealed that the coupled effect of strong upper-level divergence accompanying anti-cyclonic Rossby wave breaking and a strong low-level pressure gradient set up between the Colorado Plateau and its upwind region favored strong low-level southwesterly winds capable of emitting dust from the source region. Additionally, our simulation suggests that WRF-Chem dust transport simulation with the albedo-based drag partition in the AFWA dust emission module may be a viable tool for resolving dynamic processes and simulating dust-on-snow episodes in the southwest US.