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<p>Atmospheric Rivers (ARs) have been linked to extreme precipitation events, often resulting in widespread flooding and landslides. In the Himalayan region, ARs are a frequent cause of such disasters. Between September 25 and 29, 2024, an AR triggered large-scale flooding in the Himalayan region of Nepal. In Nepal’s Bagmati and Gandaki provinces, precipitation exceeded 450&#xa0;mm during this period. We used ERA5 reanalysis data, which includes specific humidity (q) and wind components in the zonal (u) and meridional (v) directions, for AR detection. Additionally, Potential Vorticity data from ERA5 were used to identify Rossby Wave Breaking (RWB). Geopotential height data from ERA5 were used to identify atmospheric blocking. Precipitation was analysed using GPM late-run data, and inundated areas were detected using the Normalized Difference Water Index (NDWI) and Modified Normalized Difference Water Index (MNDWI) derived from Sentinel-2 imagery. This rainfall event caused flooding in the Kathmandu Valley, inundating an area of 5.43 ± 0.45 square kilometres, primarily along the streams. It also triggered 113 landslides, particularly in Nepal’s Bagmati and Gandaki provinces. The primary cause of this AR event was an RWB over China, driven by omega-shaped blocking over Russia known as the Ural blocking. These findings highlight the critical role of large-scale atmospheric dynamics in driving extreme hydro-meteorological disasters in the Himalayas and emphasize the need to integrate AR monitoring, RWB diagnostics, and topographic vulnerability analysis into early warning systems and flood risk management frameworks for Himalayan regions to minimize future loss of life and infrastructure damage.</p>

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Role of atmospheric rivers and Rossby wave breaking in the September 2024 Nepal flooding and landslides

  • 期刊论文

  • 发表日期：

    2026年8月4日

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  • Adnan Kaisar Khan,
  • Waqar Ul Hassan,
  • Munir Ahmad Nayak

摘要

Atmospheric Rivers (ARs) have been linked to extreme precipitation events, often resulting in widespread flooding and landslides. In the Himalayan region, ARs are a frequent cause of such disasters. Between September 25 and 29, 2024, an AR triggered large-scale flooding in the Himalayan region of Nepal. In Nepal’s Bagmati and Gandaki provinces, precipitation exceeded 450 mm during this period. We used ERA5 reanalysis data, which includes specific humidity (q) and wind components in the zonal (u) and meridional (v) directions, for AR detection. Additionally, Potential Vorticity data from ERA5 were used to identify Rossby Wave Breaking (RWB). Geopotential height data from ERA5 were used to identify atmospheric blocking. Precipitation was analysed using GPM late-run data, and inundated areas were detected using the Normalized Difference Water Index (NDWI) and Modified Normalized Difference Water Index (MNDWI) derived from Sentinel-2 imagery. This rainfall event caused flooding in the Kathmandu Valley, inundating an area of 5.43 ± 0.45 square kilometres, primarily along the streams. It also triggered 113 landslides, particularly in Nepal’s Bagmati and Gandaki provinces. The primary cause of this AR event was an RWB over China, driven by omega-shaped blocking over Russia known as the Ural blocking. These findings highlight the critical role of large-scale atmospheric dynamics in driving extreme hydro-meteorological disasters in the Himalayas and emphasize the need to integrate AR monitoring, RWB diagnostics, and topographic vulnerability analysis into early warning systems and flood risk management frameworks for Himalayan regions to minimize future loss of life and infrastructure damage.