Relating Air Temperatures to the Depletion of Snow Covered Area in a Himalayan Basin

A procedure for evaluating depletion of snow covered area (SCA) using mean air temperature has been outlined and tested. Because depletion of snow is a cumulative effect of climatic conditions in and around snow cover area, the cumulative mean temperature (CTM) at a nearby station should represent depletion of SCA. The study was carried out for Satluj basin (22,305 km²) located in the western Himalayan region. Melting starts around beginning of March, therefore, reference date for computing CTM was considered March 1. Data of three ablation seasons (1987-1989) were used to establish relationship between SCA and CTM. It was found that depletion of SCA is exponentially correlated with CTM (R² > 0.98). An exponential reduction of SCA can be explained on the basis of snow distribution in the mountainous basins. This method has a potential for estimating missing data and extending time series on daily, weekly or monthly basis. Once the depletion trend is established in the basin in the first part of melt season, SCA can be simulated with good accuracy using CTM data for the rest period of melt season. Such applications can reduce the number of satellite images required for obtaining SCA information. A forecast of SCA can also be made using forecasted air temperatures. Impact of climate change on depletion of SCA over the melt period indicated that for the considered range of temperature increase (1-3°C), melting area of snow increased linearly with increase in temperature. An increase in temperature by 2°C enhanced the melting area of snow over the melt season by 5.1%.