Abstract
This study presents the reversal nature in rainfall over heavy rainfall zone (HRZ; more than 80% of the long period average (LPA) of the Indian summer monsoon rainfall (ISMR)) and low rainfall zone (LRZ; less than 40% of ISMR-LPA) in India. The India Meteorological Department (IMD) high-resolution (0.25° × 0.25°) dataset is used from 1901 to 2016. The single and multiple change-point detection techniques are used to find the change in rainfall patterns over both regions. Further, the study period is divided into two halves P1 (1901–1958) and P2 (1959–2016) to examine the change in rainfall patterns in the recent and past periods. In P2, the rainfall pattern gets reversed, and ISMR has shown a significant increasing (decreasing) trend over the LRZ (HRZ). The increasing/decreasing number of moderate- and high-intensity rainfall events is one of the causes for this reversal pattern. Additionally, the number of dry days is increased over the HRZ and decreased over the LRZ. This study further confirms that the “dry becomes drier and wet becomes wetter” paradigm is not solely acceptable for India. The present study provides information about changes in dry days and ISMR variability in the context of climate change, which will be useful to agricultural risk management, water resources, drought monitoring, model developers, and policy planner on the adaptation strategies for climate change.
Highlights
The Indian summer monsoon (ISM) is an important meteorological phenomenon, occurred in each year without failing and has the year-to-year variation (Gadgil et al, 2019) and this phenomenon is crucial for the country’s economy because more than half of the employment of India is directly or indirectly depends on agricultural and allied sectors (Economic Survey 2017-18, 2018)
This study presents the reversal nature in rainfall over heavy rainfall zone (HRZ; more than 80% of the long-period average (LPA) of the Indian summer monsoon rainfall (ISMR)) and low rainfall zone (LRZ; less than 40% of ISMR-LPA) in India
We focused our study over the Indian landmass into two regions where rainfall occurrence is less than 40% and above 80% of LPA of all-India ISMR, to perceive the changes in rainfall pattern under the umbrella of climate change
Summary
The Indian summer monsoon (ISM) is an important meteorological phenomenon, occurred in each year without failing and has the year-to-year variation (Gadgil et al, 2019) and this phenomenon is crucial for the country’s economy because more than half of the employment of India is directly or indirectly depends on agricultural and allied sectors (Economic Survey 2017-18, 2018). There are two prime hypotheses which explain monsoon circulation over India; in the first one it is believed that Indian monsoon is a gigantic land-sea breeze driven by land-sea contrast (Gadgil, 2007); alternatively, it is a movement of the Inter-Tropical Convergence Zone (ITCZ) (Gadgil, 2018). In both the hypotheses, distribution of rainfall is abiding i.e. eastern India experiences heavy rainfall and north-western part receives less rainfall. This spatial distribution of long-period average of seasonal rainfall over all India remains almost same, yearto-year fluctuation in rainfall amount is observed for ISM rainfall (ISMR)
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