Dust Trends in the Western US and their Impacts

Windblown dust is an abundant atmospheric aerosol in the western US, and a major contributor to the PM2.5 and PM10 load. Dust events in the western US, especially the exceptional events that dominate the annual dust load, have many impacts on human health and infrastructure, including respiratory health, transportation, visibility hazards, and non-attainment of air quality standards. The sources of dust in the region are both natural and anthropogenic, as well as long-range transport of dust from remote sources. Dust in the region responds to both climate and weather variability. Extended periods of wet or dry conditions can pre-condition the land surface to enhance or suppress dust emission, while regional weather patterns prompt the uplift and transport of dust, creating dust events that generally last from minutes to several hours.

This study examines the temporal trends in dust storm frequency and intensity and their correlations with local meteorology over the western US using the observed in situ near-surface dust concentration during 2001-2020 and satellite-observed dust retrievals from 2012-2020. Low- and high-concentration dust events are analyzed separately, for different seasons and sub-regions. Over the full time period we find a significant decreasing trend in the occurrence of spring and summer high-concentration dust events while the frequency of low-concentration dust events shows significant increasing trends. The correlation between these trends and climate variables such as precipitation and soil moisture vary by sub-region. Further analysis of the specific weather patterns associated with dust events in various parts of the western US identifies a set of patterns most responsible for dust occurrence. The important pattern varies geographically, and in some cases, the interannual variability of the pattern's occurrence explains the interannual variability of dust occurrence in the region. Understanding these controls on dust occurrence in the western US can help explain and predict changes to air quality on both weather and climate timescales.