Snow Distribution and Melt in Central Tien Shan, Susamir Valley

Using data collected on expeditions and long-term records, evaluations of snow accumulation and melt in high-altitude catchments, typical of much of the central Tien Shan, are presented. Over areas of about 500 km2, the main factor influencing spatial distribution of precipitation and snow is elevation. Maximum snow water equivalent, dates of maximum accumulation, and the duration of snow cover plot as a parabolic function of altitude. Over areas larger than 500 km2, the effects of rain shadow are strengthened in the cold season and precipitation decreases in eastern direction. However, during the warm season, the main predictor of precipitation and snow distribution is elevation. In areas less than 500 km2, exposure has a significant influence on snow redistribution. However, there is a similarity in snow distribution in spite of differences in elevations or the angle of inclination of slopes. Highest correlation length in snow accumulation occurred at a 50 to 60 km horizontal distance and up to 1.0 km in altitude. Solar radiation contributed 74% of energy for snowmelt and evaporation, and turbulent heat contributed 26% during expeditionary observations in May 1992. Average daily snow evaporation used 10% of available energy while snowmelt used 90%.

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