Spatiotemporal variation of snow cover and its relationship with temperature and precipitation in the Yarlung Tsangpo-Brahmaputra River Basin

The snow cover over the Qinghai-Tibet Plateau(QTP) and its surrounding areas is very sensitive to climate changes. Due to the complexity of geographical environment in this large region, the response of snow cover to climate change should exhibit spatiotemporal differences. In this study, the spatiotemporal variations of snow cover from 2002–2015 in the Yarlung Tsangpo-Brahmaputra River Basin(YBRB) were analyzed using an optimized fractional snow cover(FSC) product derived from Moderate Resolution Imaging Spectroradiometer(MODIS). Additionally, the effects of temperature and precipitation on the variability of snow cover were also investigated. The results showed that:(1) The snow cover exhibited large spatial and temporal heterogeneity in the YBRB. High FSC was observed in the northeast of the basin and the south slope of Himalaya, while the lowest was concentrated in the broad valley of the upstream of YBRB. The FSC value reached its highest in winter and dropped to its lowest in summer, but the monthly change processes were different between upstream and downstream regions.(2) A slightly increasing tendency(3.76%/10 a) of snow cover was observed on basin-wide, but the changes varied through time and space. The FSC increased significantly in the source and midstream regions during winter to spring(10.5%-18.0%/10 a), while it changed slightly in summer over all parts of the basin(-0.4%-4.3%/10 a).(3) The study area generally became warm and wet, and the change trend of temperature was more significant than that of precipitation. Snow cover changes were weakly correlated with temperature in winter and precipitation in summer. But in spring and autumn, both precipitation and temperature were significantly related to snow cover change in most regions of the basin.(4) The dominant factor driving the changes of snow cover varied in seasons. The area dominated by temperature was slightly larger than that dominated by precipitation in spring, except that precipitation significantly dominated the snow cover changes in the source region; In summer and autumn, temperature contributed more to the snow cover change in most areas of the basin; However, in winter, precipitation played a leading role in the variations of snow cover. These findings help to understand the different performance of the snow cover in the QTP and its surrounding areas under future climate change.