MONITORING DUST EMISSION IN THE SOUTHWEST U.S.—INTERANNUAL DIFFERENCES RELATED TO CLIMATIC VARIABILITY

Dust emission in the southwest U.S. is a concern with respect to soil loss, and because of its effects on air quality as well as on human health and safety. We are integrating methods to detect dust events, assess wind-erosion potential, forecast dust emissions, and evaluate the likelihood of dust-borne outbreaks of valley fever, an infectious disease caused by spores of the soil inhabiting fungus Coccidioides immitis. The main test area for dust-emission monitoring is located near Soda Lake, CA, in Mojave Desert. Studies of wind erosion that may lead to outbreaks of valley fever and are conducted near Florence, AZ, between Phoenix and Tucson. The methods include (a) analysis of remotely sensed satellite, airborne, and ground-based images of land surfaces and dust plumes; (b) monitoring meteorological, vegetation, and soil conditions, including aeolian sediment movement and flux at three sites of dust generation; (c) predictions of wind based on different meteorological models; (d) the application of a regional climate model linked with a wind-erosion model; and (e) mapping the conditions that favor the occurrence of C. immitis. Over the past three years, interannual variations in the frequency of spring-time dust emission from the central Mojave Desert were related to variations in winter precipitation and perhaps in wind strength that apparently reflected different northern hemispheric zonal flow patterns. During the spring season of 2002, very high levels of dust emission from the Mojave Desert and at least locally on the Colorado Plateau were related to very low amounts of regional, accumulated precipitation from the preceding autumn and winter, resulting in low vegetation cover. Numerous sources of dust were active in the Mojave Desert and on the Colorado Plateau during the large dust storm of April 15, 2002, when at least several tens of millions of metric tons were emitted from the central Mojave Desert alone. Geostationary satellite images document the arrival of a dust plume into the Las Vegas valley, NV, from a heavily used area about 170 km to the southwest. Large, rapid increases in levels of PM10 (particulate matter less than 10 micrometers) in the Las Vegas area corresponded with the arrival of this plume.