Snowfall Rate Reduction by Pollution Aerosols

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The hypothesis of this research is that anthropogenic aerosols increase the concentration of cloud droplets but decrease their average size, thus reducing the snowfall rate by decreasing the efficiency with which falling ice crystals sweep out the supercooled droplets. The approach is to monitor the chemical and physical properties of clouds and aerosols and the snowfall rate at the Storm Peak Observatory, a laboratory operated by the Desert Research Institute at an elevation of 3210 meters near Steamboat Springs, Colorado. At this altitude, the Observatory is frequently above cloud base during snow. The measured quantities include the size distributions of cloud droplets, ice crystals, and aerosol particles, the chemical composition of cloud water and snow, and the snowfall rate. A radar wind profiler and balloon sounding system complement the measurements at the ground by providing vertical profiles of wind, temperature, humidity, radar reflectivity, and Doppler spectra. This work has significant economic and demographic implications. If pollution aerosols are significantly reducing snowfall rates, this will decrease the amount of water available from snow pack, which in the West is an important source.