Study of temporal behaviour of meteorological drought using innovative polygon trend and scaling hypothesis methods in Kolasib district, Mizoram, India

Abstract

Abstract Drought, one of the most frequent water-related disasters, puts a great deal of strain on agriculture and associated activities in all types of climates. North-east India (NEI) having residual rainforests is also affected by this slowly unfolding disaster inspite of this region receiving the highest annual global rainfall. The multi-time scale Standardized Precipitation Index (SPI 1-month and 3-month) was used to determine the prevalence of meteorological drought in Kolasib (having humid subtropical climate, Cwa) site from Mizoram, a mountainous state situated in the southern tip of the NEI. To identify the nature of the drought, an innovative polygon trend analysis (IPTA) along with the change point detection (Pettitt and Pruned Exact Linear Time methods) and the long-term persistence (LTP) of meteorological drought under scaling theory was examined. The highest drought severity, drought duration and interval based on the SPI-1 (SPI-3) at Kolasib were observed as -11.4, 7 months from October, 1990 to April, 1991 and 176 months from March, 1996 to October, 2010 (-34.6, 17 months from December 1989 to April 1991 and 222 months from September, 1993 to February, 2012), respectively. Further, the IPTA analysis was carried out on the SPI-1 (SPI-3) month time series, and the monthly standard deviation obtained indicate that the highest decreasing trend transition occurred from May to June (July to August), i.e., trend slope of -9.45 (slope of -9.6) points of more and stronger drought event’s occurrence in crucial months of monsoon season. The PELT method observed the most drought conditions from June to August and November to January, which were almost similar to the results obtained through the IPTA. Trend analysis of drought events of both SPI-1 and SPI-3 through the LTP revealed that all twelve months observed long–term drought effect in Kolasib. The strongest LTP (Hurst estimate more than 0.90) for the SPI-3 were observed in June to September and November to January, respectively. However, no significant trends exist in the LTP, which indicated a longer drought cyclic pattern in Kolasib. It is evident from these findings that droughts in Kolasib are not only intensifying but also becoming more prolonged, necessitating proactive and science-based policy measures for drought mitigation in the region.