ABSTRACT

Adequate and consistent monsoonal rainfall is essential for the economic and societal well-being of India. Although many past studies analysed trends in Indian summer monsoon rainfall (ISMR) to capture any changes, the nature and consistency (stability) of those trends remained unexplored. Therefore, this study investigates the monotonic, non-monotonic, and trendless nature as well as the stability of ISMR trends from 1897 to 2016 using both graphical and statistical approaches for different meteorological sub-divisions of India. Also, the trend stability is examined considering high, medium, and low clusters of ISMR. Results show a predominance of monotonic trends in the long-term series, and maximum eastern sub-divisions exhibit a decreasing trend and vice versa. However, further analysis revealed instabilities in the ISMR trend and its respective clusters. The possible mechanisms behind ISMR instabilities and the spatio-temporal changes are discussed, along with certain methodological challenges, which might aid in formulating climate action plans.

摘要

充足且持续的季风降雨对印度的经济和社会福祉至关重要。尽管过去的许多研究分析了印度夏季风降雨 (ISMR) 的趋势以捕捉任何变化，但这些趋势的性质和一致性（稳定性）仍未得到探索。因此，本研究使用图形和统计方法对印度不同的气象分区，调查了 1897 年至 2016 年 ISMR 趋势的单调、非单调和无趋势性质以及稳定性。此外，考虑到 ISMR 的高、中、低集群，检查趋势稳定性。结果表明，长期序列中单调趋势占主导地位，最大东部细分呈现下降趋势，反之亦然。然而，进一步的分析揭示了 ISMR 趋势及其各自集群的不稳定性。讨论了 ISMR 不稳定性和时空变化背后的可能机制，以及可能有助于制定气候行动计划的某些方法挑战。