TY - Generic T1 - Does Dust and Pollution Aerosol Acting as Cloud Nucleating Particles Appreciably Impact Water Resources in the Colorado River Basin? T2 - 86th Annual Western Snow Conference Y1 - 2018 A1 - William R. Cotton A1 - Vandana Jha AB -

Over the last decade, there have been numerous modeling and observational studies which suggest that anthropogenic aerosol pollution such as emitted by many industries, automobile exhaust, and coal-fired power plants, are quite hygroscopic and as such can serve as particles on which cloud droplets form or what we call cloud-condensation-nuclei (CCN). In the case of wintertime orographic clouds such as in Colorado, too many CCN lead to numerous cloud droplets which are so small that they suppress rain formation by collision and coalescence of cloud droplets (not very important for those clouds), but more importantly suppress snow formation via cloud droplets being collected by ice particles or what we call riming. Previous modeling studies by our group as well as other researchers suggest that aerosol pollution will result in reduced precipitation in the Colorado mountains, particularly in relatively wet storms. Another aerosol source important to precipitation processes is wind-blown dust. While some dust particles can serve as CCN, their numbers are so few that they are not competitive with natural or pollution aerosols in rain formation or ice particle riming. But dust is also known to be the most important natural source of ice nuclei (IN). Thus, long-range transported dust and locally produced in say the four corners region flow into the Colorado mountains and essentially seed those clouds with IN, much like purposely-produced cloud seeding, and enhance precipitation from wintertime orographic clouds. Here we present the first attempt to examine the combined impact of both aerosol pollution and dust on precipitation over the Colorado mountains for an entire snow year, the months of October to April in the year 2004-2005, which is a relatively wet snow year. (KEYWORDS: dust, pollution, aerosol, cloud condensation nuclei, ice nuclei, Colorado)

JF - 86th Annual Western Snow Conference CY - Albuquerque, New Mexico UR - /files/PDFs/2018Cotton.pdf ER -