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<p>Rainfall over the complex terrain of the Northwest Himalayas (NWH) exhibits pronounced spatial and temporal variability due to interactions between topography, seasonal influences, and large-scale circulation. In this study, annual and seasonal rainfall data for 1981–2021 from the NASA POWER database (<a href="https://power.larc.nasa.gov/data-access-viewer/">https://power.larc.nasa.gov/data-access-viewer/</a>) are analyzed using robust statistical and circulation-based approaches. Rotated Empirical Orthogonal Function (REOF) decomposition identifies key spatial modes, with a few coherent modes capturing the majority of variance across all seasons. The leading modes highlight dominant rainfall centers in central Jammu &amp; Kashmir (JK), Uttarakhand (UK), and lower Himachal Pradesh (LHP), as well as Ladakh, with distinct seasonal patterns. Trend and change-point analyses reveal increasing rainfall variability across the NWH, with significant upward trends during annual and winter seasons, and regionally notable increases during the monsoon. Multiple change points are observed, particularly after the early 2000s, with one key recent change point in 2020, coinciding with the COVID-19 pandemic, during which rainfall increased at a higher rate in JK compared to other regions. Furthermore, regression of rainfall modes against upper- and mid-tropospheric circulation patterns at 200 and 500&#xa0;hPa demonstrates systematic coupling between rainfall variability and large-scale atmospheric dynamics. Monsoon rainfall is linked to southwesterly flows and enhanced geopotential height gradients, whereas winter rainfall is strongly influenced by westerly circulation and western disturbances. Moreover, teleconnection analysis highlights seasonal modulation by ENSO (SOI), NAO, and AO, reflecting the influence of remote climatic drivers. These results provide a physically consistent understanding of hydroclimatic variability in a topographically complex region and offer valuable insights for flood risk assessment, water resource management, and climate adaptation strategies in the NWH.</p>

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Spatiotemporal Rainfall Variability over the Northwest Himalayas

  • 期刊论文

  • 发表日期：

    2026年3月25日

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  • Kamana Mishra,
  • Sarita Azad

摘要

Rainfall over the complex terrain of the Northwest Himalayas (NWH) exhibits pronounced spatial and temporal variability due to interactions between topography, seasonal influences, and large-scale circulation. In this study, annual and seasonal rainfall data for 1981–2021 from the NASA POWER database (https://power.larc.nasa.gov/data-access-viewer/) are analyzed using robust statistical and circulation-based approaches. Rotated Empirical Orthogonal Function (REOF) decomposition identifies key spatial modes, with a few coherent modes capturing the majority of variance across all seasons. The leading modes highlight dominant rainfall centers in central Jammu & Kashmir (JK), Uttarakhand (UK), and lower Himachal Pradesh (LHP), as well as Ladakh, with distinct seasonal patterns. Trend and change-point analyses reveal increasing rainfall variability across the NWH, with significant upward trends during annual and winter seasons, and regionally notable increases during the monsoon. Multiple change points are observed, particularly after the early 2000s, with one key recent change point in 2020, coinciding with the COVID-19 pandemic, during which rainfall increased at a higher rate in JK compared to other regions. Furthermore, regression of rainfall modes against upper- and mid-tropospheric circulation patterns at 200 and 500 hPa demonstrates systematic coupling between rainfall variability and large-scale atmospheric dynamics. Monsoon rainfall is linked to southwesterly flows and enhanced geopotential height gradients, whereas winter rainfall is strongly influenced by westerly circulation and western disturbances. Moreover, teleconnection analysis highlights seasonal modulation by ENSO (SOI), NAO, and AO, reflecting the influence of remote climatic drivers. These results provide a physically consistent understanding of hydroclimatic variability in a topographically complex region and offer valuable insights for flood risk assessment, water resource management, and climate adaptation strategies in the NWH.