Variability and trends of rainfall and its extremes in north-western plain ACZ of India

Abstract

Graphical abstract of variability and trends of rainfall and its extremes. This study investigates rainfall trends, variability, and extreme precipitation events across 11 districts in the northwestern region of Uttar Pradesh, India, over the period 1970–2021. Utilizing daily rainfall data, the Mann–Kendall trend test and Sen's slope estimator were applied to detect temporal trends. The results indicated a widespread decline in rainfall and rainy days across the regions. The strongest declines were observed at Moradabad, Meerut, and Gautam Budh Nagar, where annual rainfall decreased by –5.93 to –7.58 mm year−1, accompanied by significant reductions in monsoon and post-monsoon rainy days. The analysis of rainfall extreme indices revealed significant decreasing trends for consecutive wet days (CWD) and total annual rainfall (PRCPTOT) at nearly 63.6% (7 out of 11) and 45.5% (5 out of 11) of districts, respectively. Heavy precipitation indices also showed declining patterns, with significant decreases recorded at 36.4% (4 out of 11) of districts for R10, 45.5% (5 out of 11) for R20, and 36.4% (4 out of 11) for RX5day. District-wise analysis indicated significant reductions in extreme rainfall events at Baghpat (RX1day: Q = –0.70; RX5day: Q = –1.26), Meerut (R20: Q = –0.11; R95p: Q = –3.35), and Moradabad (R20: Q = –0.10; RX5day: Q = –1.02). Significant declining trends in total annual rainfall (PRCPTOT) were further observed at Baghpat (Q = –4.42), Gautam Budh Nagar (Q = –4.86), Ghaziabad (Q = –4.95), Meerut (Q = –6.13), and Moradabad (Q = –4.86), highlighting an overall reduction in rainfall intensity and frequency across several locations. These findings underscore the growing impact of climate variability on regional hydrological regimes and highlight the importance of adaptive water resource management strategies in the face of changing precipitation extremes.