MESOSCALE VARIABILITY OF THE UPPER COLORADO RIVER SNOWPACK

In the mountainous regions of the Upper Colorado River Basin, snow cou rse observations give local measurements of snow water equivalent, whi ch can be used to estimate regional averages of snow conditions. We de velop a statistical technique to estimate the mesoscale average snow a ccumulation, using 8 years of snow course observations. For each of th ree major snow accumulation regions in the Upper Colorado River Basin - the Colorado Rocky Mountains, Colo orado, the Uinta Mountains, Utah, and the Wind River Range, Wyoming snow course observations yield a co rrelation length scale of 38 km, 46 km, and 116 km respectively. This is the scale for which the snow course data at different sites are cor related with 70 per cent correlation. This correlation of snow accumul ation over large distances allows for the estimation of the snow water equivalent on a mesoscale basis. With the snow course data binned int o 1/4 degrees latitude by 1/4 degrees longitude pixels, an error analy sis shows the following: for no snow course data in a given pixel, the uncertainty in the water equivalent estimate reaches 50 cm; that is, the climatological variability. However, as the number of snow courses in a pixel increases the uncertainty decreases, and approaches 5-10 c m when there are five snow courses in a pixel.