Spatiotemporal trends of cryo-climatic parameters in the Chandra Basin, Himachal Pradesh, India

Globally, the cryosphere is highly sensitive to Earth’s changing climate. The Himalayan cryosphere serves as the critical water source for millions of people downstream. The present study conducts a comprehensive long-term (1950–2024) spatiotemporal trend analysis of cryo-climatic parameters in the high-altitude Chandra Basin in the Himachal Himalaya. The study utilized the ERA5-Land reanalysis high-resolution (0.1° x 0.1°) dataset to analyze five key cryo-climatic parameters: temperature, total precipitation, rainfall, snowfall, and snow depth across monthly, seasonal, and annual timescales at both basin-wide and grid-wise scales. This study has used a multi-method statistical framework, including the Mann-Kendall & Sen’s Slope, Innovative Trend Analysis (ITA), and the Sequential Mann-Kendall (SQMK) test, to detect monotonic and sub-trends and to identify change points. Results reveal a significant warming trend (+ 0.15 °C/decade), with the strongest seasonal increases during the monsoon (+ 0.2 °C/year), winter, and pre-monsoon. SQMK analysis indicates that an accelerated upward trend started around 1990. Annual total precipitation is declining in the pre- and post-monsoon seasons. Annual rainfall shows a significant upward trend (+ 1.15 mm/year), whereas snowfall declined substantially (-3.0 mm/year), indicating a precipitation phase shift from snow to rain. The snow fraction is declining at -0.12%/year, and the mean snow depth is decreasing (-4.2 mm/year) during the critical pre-monsoon (MAM) season. Spatial analysis reveals that the eastern, higher-elevation glacierized areas are experiencing drying trends, while monsoon rainfall has increased in the western, lower-elevation areas. These warming temperatures are driving precipitation phase shifts and subsequent cryospheric degradation, posing significant risks to the regional cryosphere health, water security, and downstream agriculture and ecosystem sustainability.