Analysis of Rainfall Trends and its Spatial Patterns During the Last Century over the Gangetic West Bengal, Eastern India

  • Krishna Gopal GhoshEmail author


Long-term spatial and temporal trends of rainfall at monthly, seasonal, and annual scales have been studied for 12 meteorological stations of the Gangetic West Bengal located in Eastern India during 1901–2002 using 102 years of rainfall data. The non-parametric Mann-Kendall test and Sen’s slope estimator were used to detect trends and their slope. The changes are calculated in percentage over the time period. The results highlight a marked increase in post-monsoon (33.87%), the overall increase in annual (2.61%), a considerable decrease in winter (14.83%) as well as pre-monsoon (4.03%), and an inconsequential increase in monsoonal (1.21%) rainfall. In the annual and monsoonal series, the trend is positive in the southern half but negative in the northern counterpart. A considerable decrease in rainfall during June and August at most stations signifies that monsoon is losing in the early monsoonal months with an occurrence of mid-season dry spells. The increase in rainfall during September (13.80%) and October (34.38%) reveals that the monsoon is shifting toward these late monsoon and post-monsoon months, respectively. Both the decrease of rainfall in June (early monsoonal month), as well as an increase in rainfall in September (late monsoonal month) and October (start of post-monsoonal month), suggest that the monsoon is being delayed on its onset and withdrawal. In the Rarh region, monsoon rainfall is reducing whereas post-monsoon rainfall is increasing. In the Deltaic region, both monsoon and post-monsoon rainfalls are increasing. Such altering patterns of rainfall call for reviewing the agricultural practices and water use in this region.


Climate change Rainfall trend Gangetic West Bengal (GWB) Mann-Kendall (M-K) test Change magnitude 



An earlier version of this article was presented at the National Conference on Climate change and extreme weather: Assessment of vulnerability for early warning, held at the Asutosh Centenary Hall, Kolkata, in 2016, and I should remain thankful to Prof. Sutapa Mukhopadhyay of the Visva-Bharati University and Dr. Swades Pal of the University of Gour Banga, West Bengal, India, for their counsel during initial draft of the manuscript. Additionally, I am thankful to Mr. Debapriya Roy, officer in charge, Flood Meteorological Office, Jalpaiguri, West Bengal, for his valuable information regarding available data base and appropriate methodology to be applied. I am also indebted to the Indian Meteorological Department for providing the data. I must thank the anonymous reviewers for constructive comments and suggestions. My heartfelt thanks go to Prof. Michael P. Peterson, Department of Geography/Geology, University of Nebraska at Omaha, USA, for scrutinizing the final drafts and suggesting changes which helped sharpening the manuscript. Lastly, I should also extend my gratefulness to the Editor in Chief of this journal, Prof. Haowen Yan, for being supportive and understanding all through the process.

Authors’ contributions

No other author had a role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; and in the decision to publish the results.

Compliance with Ethical Standards

This manuscript has not been published, accepted for publication, or under editorial review for publication elsewhere.

Conflict of interest

The author declares that she has no conflict of interest.

Ethical Approval

This research does not involve individual participants in the study, and thus ethical approval is not required.


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Authors and Affiliations

  1. 1.Department of GeographyMalda CollegeMaldaIndia

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