Synoptic analysis and WRF-Chem Model simulation of dust events in the Southwestern United States

Authors: DHITAL, SAROJ - New Mexico State University; Webb, Nicholas - Nick; CHAPPELL, ADRIAN - Cardiff University; KAPLAN, MICHAEL - Desert Research Institute; NAUMAN, TRAVIS - Natural Resources Conservation Service (NRCS, USDA); TYREE, GAYLE - Us Geological Survey (USGS); DUNIWAY, MICHAEL - Us Geological Survey (USGS); EDWARDS, BRANDON - New Mexico State University; LEGRAND, SANDRA - Us Army Engineer Research And Dvelopment Center; LETCHER, THEODORE - Us Army Engineer Research And Dvelopment Center; MCKENZIE, SKILES - University Of Utah; NAPLE, PATRICK - University Of Utah; CHANEY, NATHANIEL - Duke University; CAI, JIAXUAN - Duke University

Submitted to: Journal of Geophysical Research Atmospheres
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2024
Publication Date: 7/2/2024
Citation: Dhital, S., Webb, N.P., Chappell, A., Kaplan, M.L., Nauman, T.W., Tyree, G.L., Duniway, M.C., Edwards, B., LeGrand, S.L., Letcher, T.W., McKenzie, S.S., Naple, P., Chaney, N.W., Cai, J. 2024. Synoptic analysis and WRF-Chem Model simulation of dust events in the Southwestern United States. Journal of Geophysical Research Atmospheres. 129(13). Article e2023JD040650. https://doi.org/10.1029/2023JD040650.
DOI: https://doi.org/10.1029/2023JD040650

Interpretive Summary: Dust transported from rangelands of the southwestern US to mountain snowpack in the Upper Colorado River Basin during spring (March-May) is a growing problem for water resources and agriculture. To better understand the drivers of dust-on-snow events, we investigated large-scale meteorological conditions responsible for organizing two southwest dust-on-snow episodes from two different dominant geographic locations: 1) the Colorado Plateau and 2) the northern Chihuahuan Desert. High-resolution Weather Research and Forecasting coupled with Chemistry model simulations with the Air Force Weather Agency dust emission scheme incorporating a MODIS albedo-based drag-partition was used to explore land surface-atmosphere interactions driving the dust-on-snow episodes. Our simulations reproduced the dust events and in the process we identified commonalities in their meteorological setup. The meteorological analyses revealed that Polar and Sub-tropical jet stream interaction was a common upper-level meteorological feature before each of the two dust events. When the two jet streams merged, a strong northeast-directed pressure gradient upstream and over the source areas resulted in strong near-surface winds, which lifted available dust into the atmosphere. Concurrently, a strong mid-tropospheric flow developed over the dust source areas, which transported dust to the San Juan Mountains and southern Colorado snowpack. Our results show that the simulations represented the dust sources reasonably well that contribute to dust-on-snow episodes and demonstrated the use of an albedo-based drag partition in improving dust emission and transport simulation in different geographic and meteorological conditions, which provided a basis for future dust-on-snow episode simulation to assess the hydrological impact in the Southwest US.

Technical Abstract: Dust transported from rangelands of the Southwestern United States (US) to mountain snowpack in the Upper Colorado River Basin during spring (March-May) forces earlier and faster snowmelt, which creates problems for water resources and agriculture. To better understand the drivers of dust events, we investigated large-scale meteorology responsible for organizing two Southwest US dust events from two different dominant geographic locations: (a) the Colorado Plateau and (b) the northern Chihuahuan Desert. High-resolution Weather Research and Forecasting coupled with Chemistry model (WRF-Chem) simulations with the Air Force Weather Agency dust emission scheme incorporating a MODIS albedo-based drag-partition was used to explore land surface-atmosphere interactions driving two dust events. We identified commonalities in their meteorological setups. The meteorological analyses revealed that Polar and Sub-tropical jet stream interaction was a common upper-level meteorological feature before each of the two dust events. When the two jet streams merged, a strong northeast-directed pressure gradient upstream and over the source areas resulted in strong near-surface winds, which lifted available dust into the atmosphere. Concurrently, a strong mid-tropospheric flow developed over the dust source areas, which transported dust to the San Juan Mountains and southern Colorado snowpack. The WRF-Chem simulations reproduced both dust events, indicating that the simulations represented the dust sources that contributed to dust-on-snow events reasonably well. The representativeness of the simulated dust emission and transport in different geographic and meteorological conditions with our use of albedo-based drag partition provides a basis for additional dust-on-snow simulations to assess the hydrologic impact in the Southwest US.