The influence of weather patterns and the Madden-Julian Oscillation on extreme precipitation over Sri Lanka

Sri Lanka is affected by extreme precipitation events every year, which cause floods, landslides and tremendous economic losses. In this study, we use the ERA5 reanalysis dataset to understand their association with 30 weather patterns, which were originally derived to represent the variability of the Indian climate during January–December 1979–2016. We find that weather patterns that are most common during the northeast monsoon (December–February) and second intermonsoon (October–November) seasons produce the highest number of extreme precipitation events. Furthermore, extreme precipitation events occurring during these two seasons are more persistent than those during the southwest monsoon (May–September) and first intermonsoon (March–April) seasons. We analyse the modulation of extreme precipitation events by the Madden-Julian Oscillation, and find that their frequency is enhanced (suppressed) in phases 1–4 (5–8) for most weather patterns.