Snow cover changes observed over Sikkim Himalaya

Abstract

The assessment of seasonal snow cover is an important component in the monitoring of changes in climate, which influences albedo, snow melt and affects livelihoods. The Sikkim Himalaya has a large area under snow cover and the Sikkimese depend on snow melt for recreation, economy and agricultural purposes. In this study, the snow cover pattern in Sikkim Himalaya was studied for a decade between 2002 and 2011, using the Moderate Resolution Imaging Spectroradiometer (MODIS), 8 composite snow products (500 m); which showed good reliability (89%) with the higher resolution IRS P6, and Advanced Wide Fields Sensor (AWiFS) (56 m) satellite imageries. To generate snow cover statistics from MODIS, the MODIS Snow tool Version 1.0.0, developed by ICIMOD was applied on the 8 day composite AQUA and TERRA MODIS snow products. The study showed a mean snow cover area (SCA) of 32.89 ± 6.82% (2333.84 ± 484.01 km2) in Sikkim, with a maximum mean monthly SCA in February (50.99 ± 8.94%) and November (43.16 ± 4.95), suggesting a greater snow accumulation from winter precipitation (February) than that from the north east retreating monsoon (November). The summer months of March-April (40.6 ± 7%) showed high area under snow cover, suggesting that a fairly continuous supply of precipitation during the summers, from the south-east monsoon, provided a good amount of snow input to the basin. The inter-annual variation in the SCA showed a decline of 2.81 ± 2.02% (-0.3 ± 0.18% a-1), between 2002 and 2011. The decadal SCA trend in winter (-0.85 ± 3.92%) and summer (+0.93 ± 2.45%) showed large variability, however, a significant decadal decline of 8.30 ± 5.19% in the SCA was observed in December, which related to a rise of 0.38 °C in the winter (December-February) minimum temperature. This would seem to suggest a strong influence of winter minimum air temperature on the overall decline of snow precipitation pattern in the Tista basin of Sikkim. This is a preview of subscription content, log in to check access.