Decoding trend of Indian summer monsoon rainfall using multimethod approach

Abstract

Indian monsoon rainfall has a very strong connection with the Indian economy. Any variation in trend or pattern of Indian summer monsoon rainfall will have serious implications on agronomy, water resources and various associated sectors of the economy in India. In this study, an in-depth investigation of the monsoon rainfall trend is analyzed for 146 years period (1871–2016). Three different spatial scales using a multimethod approach consisting of the Linear Regression Model (LRM), Mann Kendall Test (MKT) and Innovative Trend Analysis (ITA) are analyzed in particular and synchronized way. Monotonic trend with one or the other tests are found in Meteorological Sub-division (MetSD) 3, 4, 14, 11, 10, 19, 20, 27, 8, 29, 28, 23 and 32 (Assam, Meghalaya, Manipur, Mizoram, Nagaland, Tripura, Punjab, Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Jharkhand, Andhra Pradesh, Telangana , Konkan & Goa and Coastal Karnataka). Whereas, no significant monotonic trend was found for India as a unit. Two Homogenous Monsoon Regions (HMR) i.e. Central Northeast and Northeast have the monotonic rainfall trend. Moreover, the synchronized methodology made it possible to identify the most refined significant monotonic trend. It revealed a decreasing monotonic trend in MetSD 4, 20 and 27 (Manipur, Mizoram, Nagaland, Tripura, East Madhya Pradesh and Chhattisgarh) only. ITA based results revealed that MetSD 14, 8, 19 and 29 (Punjab, Jharkhand, West Madhya Pradesh and Telangana) are a new addition to the list of MetSDs with the significant monotonic trend. Changepoint in the trend is obtained for Northeast HMR in the year 1956 and MetSD 4, 20, 23 and 27 in the year 1969, 1961, 1930 and 1961 respectively. This study provides insight into the most refined trend on monsoon rainfall at different spatial scales in India using the updated methods of analysis.