Downslope Winds and Dust Storms in the Salton Basin

The Salton basin is a closed, subsea level basin located in extreme southeastern California. At the center of the basin lies the Salton Sea, the state's largest inland lake, which is surrounded by a desert landscape characterized by paleo lakebed surfaces, dry washes, alluvial fans, and interdunes. Dust storms are common occurrence in this region. However, despite the regularity of dust outbreaks here, little is known about the meteorological processes responsible for these storms. Here we use observations and output from reanalysis to elucidate the meteorological controls on dust emission events in the Salton basin during 2015-18. Analysis of surface and upper-air observations, satellite data, and reanalysis, suggest that the largest dust storms in the region are associated with an upper-level low centered near the coastline of western Canada, which directs a zonal low-level jet over the region. Flow blocking by a coastal mountain range results in isentropic drawdown of air in the lee of these mountains. Once surface warming at the floor of the Salton basin is sufficient such that the density of the descending air is greater than that of the ambient air at the surface, the downslope windstorm reaches the desert floor and initiates dust emission. This process may also be accompanied by a downwind propagating hydraulic jump. These processes appear to be similar to those responsible for the strongest dust events in the Owens Valley, and may represent the main mechanisms for emission from other closed basins around the planet.