Seasonal estimates of the impacts of aerosol and dust pollution on orographic precipitation in the Colorado River Basin

Abstract

ABSTRACT The cumulative effect of anthropogenic aerosol pollution acting primarily as cloud condensation nuclei (CCN) and dust acting as CCN, giant CCN, and ice nuclei (IN) is examined in this study, which covers the entire Colorado Rocky Mountains from the months of October to April in the year 2004–2005. The ~6.5-month analysis provides a range of snowfall totals and variability in concentrations of anthropogenic aerosol pollution and dust. This research quantifies the impacts of both dust and pollution aerosols on wintertime precipitation in the Colorado River Basin (CRB) using the Regional Atmospheric Modeling System (RAMS). In general, anthropogenic aerosol pollution reduces water resources in the CRB via the “spill-over” effect by enhancing cloud droplet concentrations and reducing riming, while dust enhances precipitation primarily by acting as IN. Dust is more episodic and anthropogenic aerosol is more pervasive throughout the winter season. Combined response to dust and anthropogenic aerosol is a net reduction of water resources in the CRB. The question is by how much are those water resources affected? We estimate that total winter-season precipitation loss for CRB in 2004–2005 due to the combined influence of anthropogenic aerosol and dust was 5,380,00 acre-feet of water (66.36 x 106 m3).