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<p>Precipitation is primarily administered by the monsoon wind system across the Indian subcontinent. The inherent rainfall variability poses significant challenges in making appropriate water resources management decisions under rainfed agricultural conditions. This complexity is further exaggerated in the Indian state of West Bengal (WB) due to its exclusive geographical setting and varied climatic conditions. To decipher the long-term rainfall variability at seasonal and annual scale of WB, the spatiotemporal rainfall trends (1990–2019) have been analyzed across regional scale using conventional and innovative approaches. it reveals that the Gangetic WB (GWB) received 47–55% less rainfall 73–78% negative percent departure of rainfall (PDR) during pre-monsoon, monsoon and annually respectively as compared to ACZs of Sub-Himalayan WB (SHWB). Conversely, GWB received 5–12% more rainfall with 52% positive PDR during winter and post-monsoon seasons as compared to SHWB. Seasonal and annual rainfall in WB exhibited steady positive anomalies until 2000–2004, subsequently, there was a shift to negative anomalies and a steady decline. This variation was reaffirmed with inter-annual rainfall variability, which exhibited most consistent rainfall pattern for Northern Hill Zone and Terai-Teesta Alluvial Zone which covers a major part of SHWB. In contrast, major variation, with deficit to large deficit rainfall was observed in GWB consisting of Gangetic Alluvial Zone, Costal Saline Zone and Undulating Red and Laterite Zone. Seasonal/ annual rainfall trends were analysed and compared using Mann–Kendall (MK), modified MK test (mMK), Sen’s slope estimator, and innovative trend analysis (ITA) methods. The study detected significantly (<i>p</i> &lt; 0.05 or <i>p</i> &lt; 0.01) declining rainfall trends in 78–95% of the districts in WB by ITA method, with sharpest reduction observed in Costal Saline Zone (Medinipur-East), Vindhyan Alluvial Zone (Dinajpur-Dakshin), Northern Hill Zone (Darjeeling) and Vindhyan Alluvial Zone (Dinajpur-Dakshin) during pre-monsoon, monsoon, post-monsoon and annual period respectively. In contrast, Terai-Teesta Alluvial Zone showed a consistent positive rainfall trend with the district Jalpaiguri, which exhibited the sharpest increasing rainfall trends in pre-monsoon, monsoon and annual time scale. Based on the comparison of different trend analysis methods, ITA has been found the most sensitive in identifying more hidden time series rainfall trends than MK, mMK or Sen’s slope estimator. Spatio-temporal clustering of districts using ITA derived rainfall slope revealed 5 major clusters. Among those, cluster 1 (covering Vindhyan Alluvial Zone, and parts of Northern Hill Zone and Coastal Saline Zone) showed the sharpest decreasing slope followed by cluster 5 which covers largest number of districts (11) in ACZ Gangetic Alluvial Zone and part of Undulating Red and Laterite Zone. Each subsequent decade, beginning from 2000, showed decreasing pattern in monsoon rainfall with more negative rainfall anomaly which emphasizes climatic vulnerability i.e., rising hydro-climatic stress in the state. Additionally, we provided perceptions into spatio-temporal rainfall variations based on recent theories, along with potential impacts and adaptation strategies. ENSO indices, particularly Niño 3.4, ONI, MEI, and DMI, significantly influenced the seasonal rainfall variability in West Bengal, but the overall declining trend indicates that even La Niña events might not fully offset El Niño–induced drought risks. The findings of the current study will be useful in strategic planning and mitigating climate change impacts and help in understanding changes in rainfall climatology which may assist the policymakers and beneficiaries in optimizing the use of hydrological resources.</p>

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Deciphering spatiotemporal rainfall dynamics and tele-connections of West Bengal using conventional and innovative approaches: evidence of rising hydro-climatic stress

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月30日

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  • Koushik Banerjee,
  • K. G. Mandal,
  • S. K. Purbey,
  • Bappa Das,
  • Shreya Nivesh,
  • Vikas Paradkar,
  • Ravi Kumar

摘要

Precipitation is primarily administered by the monsoon wind system across the Indian subcontinent. The inherent rainfall variability poses significant challenges in making appropriate water resources management decisions under rainfed agricultural conditions. This complexity is further exaggerated in the Indian state of West Bengal (WB) due to its exclusive geographical setting and varied climatic conditions. To decipher the long-term rainfall variability at seasonal and annual scale of WB, the spatiotemporal rainfall trends (1990–2019) have been analyzed across regional scale using conventional and innovative approaches. it reveals that the Gangetic WB (GWB) received 47–55% less rainfall 73–78% negative percent departure of rainfall (PDR) during pre-monsoon, monsoon and annually respectively as compared to ACZs of Sub-Himalayan WB (SHWB). Conversely, GWB received 5–12% more rainfall with 52% positive PDR during winter and post-monsoon seasons as compared to SHWB. Seasonal and annual rainfall in WB exhibited steady positive anomalies until 2000–2004, subsequently, there was a shift to negative anomalies and a steady decline. This variation was reaffirmed with inter-annual rainfall variability, which exhibited most consistent rainfall pattern for Northern Hill Zone and Terai-Teesta Alluvial Zone which covers a major part of SHWB. In contrast, major variation, with deficit to large deficit rainfall was observed in GWB consisting of Gangetic Alluvial Zone, Costal Saline Zone and Undulating Red and Laterite Zone. Seasonal/ annual rainfall trends were analysed and compared using Mann–Kendall (MK), modified MK test (mMK), Sen’s slope estimator, and innovative trend analysis (ITA) methods. The study detected significantly (p < 0.05 or p < 0.01) declining rainfall trends in 78–95% of the districts in WB by ITA method, with sharpest reduction observed in Costal Saline Zone (Medinipur-East), Vindhyan Alluvial Zone (Dinajpur-Dakshin), Northern Hill Zone (Darjeeling) and Vindhyan Alluvial Zone (Dinajpur-Dakshin) during pre-monsoon, monsoon, post-monsoon and annual period respectively. In contrast, Terai-Teesta Alluvial Zone showed a consistent positive rainfall trend with the district Jalpaiguri, which exhibited the sharpest increasing rainfall trends in pre-monsoon, monsoon and annual time scale. Based on the comparison of different trend analysis methods, ITA has been found the most sensitive in identifying more hidden time series rainfall trends than MK, mMK or Sen’s slope estimator. Spatio-temporal clustering of districts using ITA derived rainfall slope revealed 5 major clusters. Among those, cluster 1 (covering Vindhyan Alluvial Zone, and parts of Northern Hill Zone and Coastal Saline Zone) showed the sharpest decreasing slope followed by cluster 5 which covers largest number of districts (11) in ACZ Gangetic Alluvial Zone and part of Undulating Red and Laterite Zone. Each subsequent decade, beginning from 2000, showed decreasing pattern in monsoon rainfall with more negative rainfall anomaly which emphasizes climatic vulnerability i.e., rising hydro-climatic stress in the state. Additionally, we provided perceptions into spatio-temporal rainfall variations based on recent theories, along with potential impacts and adaptation strategies. ENSO indices, particularly Niño 3.4, ONI, MEI, and DMI, significantly influenced the seasonal rainfall variability in West Bengal, but the overall declining trend indicates that even La Niña events might not fully offset El Niño–induced drought risks. The findings of the current study will be useful in strategic planning and mitigating climate change impacts and help in understanding changes in rainfall climatology which may assist the policymakers and beneficiaries in optimizing the use of hydrological resources.