Synoptic Analysis and WRF-Chem Model Simulation of Dust Events in the Southwestern United States

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. Dust transported from rangelands of the Southwestern United States (US) to the mountain snowpack in the Upper Colorado River Basin during spring (March-May) is a growing problem for water resources and agriculture. Understanding the drivers of dust events is essential to better forecast the possible impact of dust on water resources. We investigated the weather conditions that led to two dust events originating from the Colorado Plateau and northern Chihuahuan Desert. We also performed computer simulations with an improved dust emission model to explore the influence of vegetation on the susceptibility of landscapes to wind erosion during dust events. Our meteorological analysis revealed commonalities in the upper-level meteorology before dust event formation and provided valuable insights into where and when high-impact dust events may occur. However, further investigation is needed to generalize the impact of jet stream interaction on dust events' intensity. Our simulations represented the dust sources reasonably well by using an improved dust emission model. The improved dust emission and transport simulation under different meteorological and geographical conditions provided a basis for future dust-on-snow simulations to assess the hydrological impact in the Southwestern US. Large-scale meteorological analysis and dust emission and transport simulation of Southwest US dust-on-snow events Polar and Sub-tropical jet stream interaction was a common upper-level meteorological feature to Southwest US dust events Simulated dust source areas on the Colorado Plateau and Chihuahuan Desert reflect observed dust emission hot spots