Abstract
A comprehensive study on the Indian summer monsoonal rainfall (ISMR) is performed in the light of decadal changes in the continuous rainfall events and the number of rainy days using 68 years (1951–2018) of gridded rain gauge data. Non-parametric Mann–Kendall’s test is applied on total rainfall amount, the number of rainy days, number of continuous rainfall events, and rainfall magnitude to find trends over different climatic zones of India for the two periods, 1951–1984 and 1985–2018. Our results found a decreasing trend for more than 4-days of continuous rainfall events during the recent 34 years (1985–2018) compared to 1951–1984. The rate of increase/decrease in extreme/continuous rainfall events does not follow a similar trend in number of continuous rainfall events and magnitude. Moreover, the rainfall is shifted towards a lesser number of continuous rainfall days with higher magnitudes during 1985–2018. During the crop’s sow season (i.e., the first 45 days from the onset date of Indian monsoon), the total number of rainy days decreased by a half day during the last 34 years. Over the Central and North East regions of India, the number of rainfall days decreased by ~0.1 days/yr and ~0.3 days/yr, respectively, during 1985–2018. Overall, the decreasing trends in continuous rainfall days may escalate water scarcity and lead to lower soil moisture over rain-fed irrigated land. Additionally, an upsurge in heavy rainfall episodes will lead to an unexpected floods. On a daily scale, rainfall correlates with soil moisture and evaporation up to 0.87 over various land cover and land use regions of India. Continuous light-moderate rainfall seems to be a controlling factor for replenishing soil moisture in upper levels. A change in rainfall characteristics may force the monsoon-fed rice cultivation period to adopt changing rainfall patterns.
Highlights
The summer monsoonal rainfall variability over different regions in India directly affects the growth of rain-fed crops and socio-economic structure [1]
West Coast (WC) and North East (NE) regions show the highest number of rainy days (Figure 1a), which resembles spatial patterns with the composite of active-spells
Few studies have highlighted the usefulness of rain harvesting, in regions that receive moderate to low rainfall so that the stored water could locally be utilized during monsoon breaks and droughts [29]
Summary
The summer monsoonal rainfall variability over different regions in India directly affects the growth of rain-fed crops and socio-economic structure [1]. Summer (June to September, JJAS) is the only season that brings plentiful rainfall to most parts of. India receives about 75% to 80% of the total annual rainfall during JJAS, which is vital for the irrigation of kharif crops (Crops that are sown in summer in the Indian subcontinent), especially rice [2,3]. The plantation of the staple crop (rice) starts from May to. This plantation almost follows the climatological isochrones of rainfall [3,4]. In fewer cases, the plantation of rice could be delayed up to August
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
