A framework is developed to study variations in winter season precipitation and snow processes and spring season runoff in the alpine basins of the southwestern United States. The framework exploits available high-elevation precipitation and snow water equivalent (SWE) data, and a regional climate model (RegCM) to study two contrasting winter/spring seasons (1994 and 1995). This work examines the influences of large-scale atmospheric conditions on cold season hydrology in the Southwest, assesses the capability of the regional climate model for simulating snowpack and runoff in two major alpine basins and evaluates methodologies fop employing high-elevation observations on regional spatial scales and seasonal time-scales. High elevation data and streamflow measurements from the winter/spring of 1995 show relatively wet conditions, larger snow accumulations and more substantial springtime streamflows in the Rocky Mountains and Sierra Nevada than observations from 1994. Analysis of the large scale atmosphere and surface station data during these periods reaffirms that the wintertime quasi-stationary wave across North America is an important modulator of precipitation, snowpack, and streamflows in the west. The RegCM simulates the large-scale circulations in these 2 years well. Errors are apparent in the simulated precipitation fields and are greater when comparing modeled and observed snowpack and runoff. While the simulated snowpack/streamflow errors are controlled by precipitation deficiencies in the Rocky Mountain region, in the Sierra Nevada region the errors are determined by elevation and associated temperature errors. Despite an underprediction of snowpack and runoff, the model is able to reproduce the overall patterns of precipitation and snowcover and to some extent the year to year hydrologic variations. Continued time series of the data employed in this study (high-elevation precipitation and SWE and streamflow measurements) are crucial for seasonal and interannual studies of mater resources in the west.
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