Extreme precipitation events are among the most significant climatic phenomena that can cause widespread damage on local to regional scales within a short period of time. One of the primary systems influencing heavy summer rainfall over Asia is the Indian monsoon, whose variations in intensity and position can substantially alter precipitation patterns in surrounding regions. During the summer of 2022, large parts of Iran experienced intense rainfall and devastating floods. This event affected 26 provinces, caused the death of more than 80 people, and led to severe losses in infrastructure and agriculture. Concurrently, India experienced an exceptionally strong monsoon season; the country’s total rainfall in July 2022 was about 17 % above the long-term climatological mean.
Using a large-scale synoptic approach, this study investigates the dynamic and statistical mechanisms associated with this extreme event. The NCEP/NCAR reanalysis data were used to analyze atmospheric circulation fields, the ERA5 reanalysis to calculate the Indian Monsoon Index (IMI), and monthly satellite-based GPM precipitation data to examine rainfall over Iran. Anomalies of geopotential height, horizontal wind, and vertically integrated moisture flux convergence were computed at several pressure levels for July 2022. In addition, to evaluate the temporal linkage between the monsoon and rainfall, the Pearson correlation coefficient between the IMI and monthly precipitation at twenty points with the highest positive rainfall anomalies in southern Iran was calculated for both simultaneous (Lag 0) and one-month-lagged (Lag +1) phases.
The results indicate that the IMI value in July 2022 exceeded its long-term mean by more than two standard deviations, representing one of the strongest monsoon phases in the past four decades. Correlation coefficients between the IMI and precipitation exceeded 0.4 and were statistically significant at the 95% confidence level south of 30° N, while the relationship weakened at higher latitudes. The moisture-anomaly pattern further revealed enhanced moisture transport from the Bay of Bengal and the Arabian Sea toward southern Iran, leading to increased convergence and intensified rainfall. Overall, the findings highlight that the exceptionally strong Indian monsoon phase in summer 2022 was the principal driver of Iran’s extreme precipitation and associated floods.