Downslope Winds and Dust Storms in the Salton Basin

Abstract

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 I 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.

Global climatology of synoptically‐forced downslope winds

“…However, some exceptions are evident including along the western slope of the Wasatch Range, and offshore (easterly) winds can be found from the Cascades to the Coastal Ranges and Sierra Nevada of California (Reed, 1981). Downslope winds across southern California include both onshore winds (e.g., Evan, 2019) and offshore winds including SAW (Figure 3c), Diablo, and Sundowner winds. We find a similar climatology of offshore downslope winds across southern California to previous SAW approaches with a distinct peak in winter (Figure 3d, Abatzoglou et al ., 2013; Guzman‐Morales et al ., 2016).…”

“…From a societal perspective, the seasonal and geographic distribution of downslope winds helps to identify potential risks to infrastructure and other wind‐related hazards, including those tied to wind energy, power outages, transportation, and fire ignitions. Finally, meteorological downslope winds have also been shown to impact air quality (Li et al ., 2015; Aguilera et al ., 2019), and pose an array of adverse effects to human health via entrainment and transport of dust (Evan, 2019), smoke transport downwind of wildfires fanned by the same winds (Delfino et al ., 2009; Leibel et al ., 2019), and heat impacts on valley and coastal populations at the terminus of downslope winds (Schwartz et al ., 2019). Our database and conceptual model set the stage for evaluating downslope windstorm impacts and physical mechanisms, as well as plausible changes in downslope winds simulated by global models under a warming climate.…”

“…Summary statistics span the 1979-2018 period and were smoothed using a 21-day moving mean and 1 latitude moving mean. Latitudinal bands with no suitable land are shown in white [Colour figure can be viewed at wileyonlinelibrary.com] (e.g., Evan, 2019) and offshore winds including SAW (Figure 3c), Diablo, and Sundowner winds. We find a similar climatology of offshore downslope winds across southern California to previous SAW approaches with a distinct peak in winter (Figure 3d, Abatzoglou et al, 2013;Guzman-Morales et al, 2016).…”

Measurements of a Dusty Density Current in the Western Sonoran Desert

“…Synoptic weather systems, particularly during the fall through spring seasons, oftentimes traverse eastward through the region (Evan, 2019), and as such the Peninsular range acts as a barrier to this zonal flow. A zonal transect of elevation, made at the latitude of the SIO Salton Sea research site, shows that the peninsular range is steep and nearly symmetric, although heights fall off more rapidly to the east of the ridge.…”

“…Within the center of the Salton Basin lies the Salton Sea, which is a spatially vast, yet shallow inland body of water. Dust storms are a frequent occurrence in this region (Bach et al., 1996; Evan, 2019), which is due in part to the prevalence of erodible soils (Buck et al., 2011; Sweeney et al., 2011).…”