Regional and climatic controls on seasonal dust deposition in the southwestern U.S.

Abstract

a b s t r a c tVertical dust deposition rates (dust flux) are a complex response to the interaction of seasonal precipitation, wind, changes in plant cover and land use, dust source type, and local vs. distant dust emission in the southwestern U.S. Seasonal dust flux in the Mojave-southern Great Basin (MSGB) deserts, measured from 1999 to 2008, is similar in summer-fall and winter-spring, and antecedent precipitation tends to suppress dust flux in winter-spring. In contrast, dust flux in the eastern Colorado Plateau (ECP) region is much larger in summer-fall than in winter-spring, and twice as large as in the MSGB. ECP dust is related to wind speed, and in the winter-spring to antecedent moisture. Higher summer dust flux in the ECP is likely due to gustier winds and runoff during monsoonal storms when temperature is also higher. Source types in the MSGB and land use in the ECP have important effects on seasonal dust flux. In the MSGB, wet playas produce salt-rich dust during wetter seasons, whereas antecedent and current moisture suppress dust emission from alluvial and dry-playa sources during winter-spring. In the ECP under drought conditions, dust flux at a grazed-and-plowed site increased greatly, and also increased at three annualized, previously grazed sites. Dust fluxes remained relatively consistent at ungrazed and currently grazed sites that have maintained perennial vegetation cover. Under predicted scenarios of future climate change, these results suggest that an increase in summer storms may increase dust flux in both areas, but resultant effects will depend on source type, land use, and vegetation cover.Published by Elsevier B.V.

Quantifying dust emissions from desert landforms, eastern Mojave Desert, USA

“…Greater than normal precipitation in winter months leads to the growth of annual plants can that dramatically reduce wind erosion potential of alluvial sources (MacKinnon et al, 2004;Urban et al, 2009;Reheis and Urban, 2011). Alternatively, high dust emissions are not always correlated to drought, as some of the highest dust fluxes in the last decade occurred in 2005 following a wet winter (Reheis and Urban, 2011). Documented increases in dust flux correspond to both strong El Niño (wet) and La Niña (dry) years (Okin and Reheis, 2002).…”

“…Most wind erosion in the Mojave occurs in the winter and spring due to high winds, but vegetation density is highest during this time due to winter moisture (Bach et al, 1996). Greater than normal precipitation in winter months leads to the growth of annual plants can that dramatically reduce wind erosion potential of alluvial sources (MacKinnon et al, 2004;Urban et al, 2009;Reheis and Urban, 2011). Alternatively, high dust emissions are not always correlated to drought, as some of the highest dust fluxes in the last decade occurred in 2005 following a wet winter (Reheis and Urban, 2011).…”

“…Other researchers have documented seasonality of dust emissions from wet playa settings producing efflorescent salts, with most emissions occurring in winter or spring months (Stout, 2003;Reynolds et al, 2007;Reheis and Urban, 2011). Seasonality of emissions is often a function of landform type in the Mojave Desert, with wet playas showing more seasonal variability than dry playas or alluvial sources (Reheis and Urban, 2011).…”

Dust Climatology of the NASA Dryden Flight Research Center (DFRC) in Lancaster, California, USA

“…It is also a major geomorphological factor for land degradation in arid regions [18]. High concentrations of dust at the local level may indicate agricultural soils are being degraded by the loss of fine particles [19]. Many previous studies have shown a positive correlation between drought years and increased dust emission [18,20], while others indicated the entry of dust in the atmosphere occurs once the freshly deposited sediment brought by the intense storms becomes desiccated [21].…”

“…Although a number of studies about the origin, transport, and deposition of desert dust are available [19,23,28,33,34], a detailed understanding of the climatological and meteorological characteristics that influence dust event frequency and magnitude for sub-regions of the southwestern region of the U.S. are still lacking. This type of knowledge is needed to understand the regional and local dust climatology.…”