Assessing the consistency of trends in Indian summer monsoon rainfall

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.

KEYWORDS:

• India
• monsoon rainfall
• stability
• Mann-Kendall
• innovative trend analysis
• time series

Editor A. CastellarinAssociate editor E. Hassanzadeh

Editor A. CastellarinAssociate editor E. Hassanzadeh

Acknowledgements

We acknowledge the Indian Institute of Tropical Meteorology, Pune, India, for providing the ISMR data. Furthermore, the authors are grateful to the Editor-in-Chief, the Associate Editor, and the reviewers for their critical review and constructive suggestions. Additionally, we express our sincere gratitude to Dr Yavuz Selim Güçlü (Associate Professor, Istanbul Medeniyet University) for the informative response to our queries, which helped us improve the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/02626667.2022.2081507.