Extended Abstract (444K)P2.22
Mountaintop and radar measurements of snow growth and snowfall rate
Randolph D. Borys, Storm Peak Laboratory, Steamboat Springs, CO; and D. H. Lowenthal, S. Cohn, and W. O. J. Brown
 During the first field season of ISPA (Inhibition of Snowfall by Pollution Aerosol) in 2001, measurements of cloud and precipitation chemical and physical properties were made in the vicinity of Steamboat Springs, Colorado from a remote sensing site in the valley and from a mountaintop laboratory. Desert Research Institute’s Storm Peak Laboratory (SPL, 3220m AMSL) was used to monitor the cloud microstructure, including droplet and ice particle size distributions, ice particle habits, rime extent, and snowfall rates. Chemical and isotopic analysis of cloud and snow water samples were also performed. In the valley upwind of and 1.1 km lower in elevation than SPL, the National Center for Atmospheric Research, Atmospheric Technology Division, Integrated Sounding System (ISS) was deployed, including a rawinsonde sounding system, a vertically pointing 915 MHz Doppler clear-air wind profiler radar, a Radio Acoustic Sounding System (RASS), and an enhanced surface observing system. The system provided information on cloud base and cloud top heights, vertical resolution of snowfall velocities and regions of rime- enhanced ice particle growth, and surface snowfall rates.
Simultaneous measurements at both sites were used to compare the in-situ and remote observations to assess the areal validity of the mountaintop measurements. We present the results from two days in February, 2001 to contrast the cloud and snow microphysical properties during periods of relatively high and low aerosol pollution content. The results indicate that elevated levels of pollution aerosol act as cloud condensation nuclei which alter the cloud droplet size distribution so that the smaller and more numerous droplets do not accrete on the snow particles, thus reducing the flux of snow water equivalent to the surface.
Supplementary URL: http://www.dri.edu/Projects/SPL
Poster Session 2, Orographic Precipitation/Operational and Numerical Weather Prediction (with Coffee Break)
Wednesday, 19 June 2002, 9:15 AM-11:00 AM
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