Inter-annual variation in precipitation totals is a critical factor governing the year-to-year availability of water resources, yet the connection between inter-annual precipitation variability and underlying event- and season-scale precipitation variability remains unclear. In this study, tropical and mid-latitude precipitation characteristics derived from extensive station records and high frequency satellite observations were analyzed to attribute the fraction of inter-annual variability arising due to individual variability in precipitation event (i) intensity, (ii) frequency, and (iii) seasonality, as well as the cross-correlation between these factors at the global scale. This analysis demonstrates that variability in the length of the wet season is the most important factor globally, causing 52% of the total inter-annual variability, while variation the intensity of individual rainfall events contributes 31% and variability in inter-storm wait times contributes only 17%. Spatial patterns in the contribution of each of these intra-annual rainfall characteristics are informative, with regions such as Indonesia and south-western North America primarily influenced by seasonality, while regions such as the eastern United States, central Africa, and the upper Amazon are strongly influenced by storm intensity and frequency. A robust cross-correlation between climate characteristics is identified in the equatorial Pacific, revealing an increased inter-annual variability over what is expected based on the variability of individual events. This decomposition of inter-annual variability identifies those regions where accurate representation of daily and seasonal rainfall statistics is necessary to understand and correctly model rainfall variability at longer times scales.

 

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