ANALYSIS OF LONG TERM SPATIO-TEMPORAL TREND OF RAINFALL IN TAMIL NADU, INDIA

Abstract

In recent decades, the escalation of human activities has played a pivotal role in driving substantial global climate change. This research primarily centers its attention on the assessment of changes occurring in the spatio-temporal distribution of rainfall in Tamil Nadu over a 40-year period. The study area comprises 32 districts of Tamil Nadu, India and a comprehensive dataset spanning four decades (1981-2020) of monthly precipitation of each district was acquired from both the Tamil Nadu Agricultural University and the India Meteorological Department. Subsequently, various statistical methodologies were employed to analyze this extensive rainfall data. The Seasonal Precipitation Concentration Index (SPCI) was scrutinized for both the southwest and northeast monsoon. The findings revealed that SPCI values < 10 indicated a relatively uniform distribution of rainfall during the southwest monsoon, while values > 10 indicated more extreme weather conditions during the northeast monsoon. Statistical analyses, including the Mann–Kendall non-parametric test, were conducted using trend analysis software for both monsoon seasons. Notably, a significant upward trend in rainfall was observed during the southwest monsoon in locations such as Coimbatore (1.8 mm/season/year), Erode (2.1 mm/season/year), Perambular (2.1 mm/season/year), Theni (2.0 mm/season/year), and Tirunelveli (2.4 mm/season/year). Conversely, a significant decrease in rainfall was noted in Namakkal (2.5 mm/season/year) during the same period. In contrast, the northeast monsoon displayed a significant increase in rainfall in areas like Kancheepuram (2.4 mm/season/year), Tuticorin (2.6 mm/season/year), and Villupuram (2.0 mm/season/year).