Solar activity and extreme rainfall over Kerala, India

TL;DR

This study investigates the correlation between solar activity and extreme rainfall events in Kerala over 57 years, finding significant links especially during Solar Cycle 21, and suggests a potential for rainfall prediction based on solar indices.

Contribution

It provides a detailed analysis of the relationship between solar activity and rainfall in Kerala, highlighting the significance during specific solar cycles and proposing a physical link for predictability.

Findings

Rainfall correlates with solar activity, especially during Solar Cycle 21.

Years of rainfall surplus or deficit align with solar maximum or minimum.

Winter rainfall shows a stronger link to solar activity than monsoon rainfall.

Abstract

This paper examines the relationship between solar activity and extreme rainfall events in Kerala, India. Kerala receives minimum and maximum rainfall during winter and monsoon seasons. Sunspot number, F10.7 Index, and cosmic ray intensity are the solar indices considered, and their variations with rainfall are studied over 57 years (1965-2021), i.e., starting from Solar Cycle 20. Correlative studies are performed for each solar cycle, and correlation coefficients are calculated. We find that rainfall in Kerala is correlated with sunspot activity but with varying degrees of significance. During Solar Cycle 21, rainfall and solar activity are correlated with high significance during both winter and monsoon seasons. The variation of different solar indices with rainfall is studied. The winter season showed a better link between the sun and rainfall than the monsoon season. The years with rainfall surplus and deficiency are calculated and compared with the solar indices. {We find that the years with rainfall excess and deficit mainly occur in the years around solar maximum or minimum (within $\pm$2 years).} We hypothesize a physical relationship between solar activity and extreme rainfall events in Kerala that contributes to their predictability.