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Title: Characterizing rainfall occurrence in India: Natural variability and recent trends
Authors: Pal L.
Ojha, C. S. P.
Dimri A.P.
Published in: Journal of Hydrology
Abstract: A deficit in rainy days can affect crop production and escalate groundwater abstraction leading to groundwater depletion, thus may threaten food and water security in the Indian subcontinent. The available researches on rainfall occurrence in India represent inconsistency in several fundamental considerations (spatial scale of analysis, the definition of rainfall classes, methods, dataset, study period, etc.) and lack of studies for non-monsoon seasons over large parts of the subcontinent. Here we attempt to deal with these inconsistencies by examining space–time patterns in seasonal count of rainfall events and their count in different rainfall classes during 1951–2015 for all meteorological seasons of India using high resolution (0.25°) gridded daily rainfall dataset. The results show a widespread decline in monsoon rainy days over major crop-growing regions including north-central, central, and northeast India. A reduction in rainy days is also observed over parts of central India in premonsoon; over north-central and northeast India in postmonsoon; and over peninsular India in winter. These trends are mainly observed in events with rainfall <95th percentile (light to heavy rainfall events) in all the seasons. Occurrence of extreme events (above 95th and 99th percentile) exhibits contrasting trends over different zones with mainly an increase over central and south-central India and decline over central-north India. However, trends in extremes are highly dispersed in space and are conclusive only over a few regions. The observed trends substantially deviate from the patterns reported in past studies for different regions. Rainfall occurrence in different meteorological zones also represents strong interannual and decadal variability, however, the observed trends have emerged beyond the inherent natural variability. The present findings provide an essential foundation for several future explorations with improved understanding of change in rainfall frequency and its possible impacts. It would also assist in developing a comprehensive framework for year-wide management of water resources and agriculture, considering all crop seasons. © 2021 Elsevier B.V.
Citation: Journal of Hydrology, 603
Issue Date: 2021
Publisher: Elsevier B.V.
Keywords: Rainfall frequency
Rainfall occurrence
Rainfall variability
Rainy days
Trend analysis
ISSN: 221694
Author Scopus IDs: 57204417883
Author Affiliations: Pal, L., Civil Engineering Department, Indian Institute of Technology Roorkee, Roorkee, 247667, India
Ojha, C.S.P., Civil Engineering Department, Indian Institute of Technology Roorkee, Roorkee, 247667, India
Dimri, A.P., School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
Funding Details: The authors thank Prof. Donald H. Burn (University of Waterloo) for sharing the code for trend analysis of count variable proposed by Frei and Sch?r. We also thank India Meteorological Department (IMD) for making available the daily gridded precipitation data.
Corresponding Author: Pal, L.; Civil Engineering Department, Roorkee 247667, India; email:
Appears in Collections:Journal Publications [CE]

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