Contrasting changes of snowfall in response to temperature and rainfall over two distinct geographic ranges of the Himalayas: A study using the High Asia Refined analysis data

Snow is a major source of water and its monitoring is important for hydrological applications. It provides meltwater to various rivers such as the Indus, Ganges, and Brahmaputra in the Himalayan region. Significant changes in snowfall variability play a pivotal role in climate. The present study investigates the temporal variability of snowfall, temperature, and rainfall over Nubra (latitude: 34.53 degrees-35.67 degrees N; longitude: 76.75 degrees-77.81 degrees E) and Bhagirathi (latitude: 30.33 degrees-31.45 degrees N; longitude: 78.15 degrees-79.47 degrees E) basins in the Himalayan region using 30 yrs of reanalysis data (1991-2020). The High Asia Refined analysis (HAR) and Climatic Research Unit (CRU) data were used to study the snowfall and maximum air temperature variabilities, respectively, over the study basins. For rainfall, high-resolution (0.25 degrees x 0.25 degrees) gridded rainfall data from the India Meteorological Department is used. We have studied the annual and monthly variability of daily snowfall, temperature and rainfall over the two basins. Our analysis shows the declining trend (-2 mm/decade) of snowfall over the Nubra basin and a slightly increasing trend (0.12 mm/decade) in the Bhagirathi basin from 2004. The monthly time series in maximum temperature anomaly shows a positive trend with a maximum anomaly found to be around 2 K during the winter period. From the rainfall analysis, an increasing trend in annual rainfall is observed, especially Nubra basin showing a notable increase. Further, warming of the troposphere is found to be similar to 2-3 K, which is another important factor for the reduction in snowfall. Thus, positive trends in maximum temperature, rainfall and warming troposphere are the controlling factors for the declining (increasing) trend in snowfall over the Nubra (Bhagirathi) basins. Thus, the present study shows simultaneous changes in snowfall, temperature and rainfall over the Himalayan region and assumes importance in climatic applications.

Automated summary

This study investigates the temporal variability of snowfall, temperature, and rainfall over Nubra and Bhagirathi basins in the Himalayan region. The analysis shows a declining trend in snowfall over the Nubra basin and a slightly increasing trend in the Bhagirathi basin. The maximum temperature anomaly exhibits a positive trend during the winter period. Furthermore, an increasing trend in annual rainfall, especially in the Nubra basin, is observed.