Article Dans Une Revue Atmospheric Research Année : 2026

Widespread extreme precipitation events over Iran: Large-scale patterns and their associated global indices

Résumé

Widespread extreme precipitation events (WEPEs) have intensified globally in recent decades, leading to severe hydrological and socio-economic impacts. Iran has experienced several destructive WEPEs, particularly during 2019 and 2020. Using Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG-F) data for 2000–2024, extreme precipitation events (EPs) were classified as WEPEs when their spatially connected affected area exceeded 10% of Iran's land area. A total of 153 WEPEs were identified across all seasons. Owing to the dominant contribution of winter and spring events, subsequent large-scale analyses focused on these two seasons, comprising 135 events (80 in winter and 55 in spring). Evaluation against observations from 39 synoptic stations on IMERG-identified WEPE days, indicates that IMERG-F reliably captures the frequency and intensity of EPs during WEPEs, supporting its use for long-term WEPE analysis. Cluster analysis using Ward's method delineated three spatial sub-regions were identified: R1 (western and northwestern Iran), R2 (eastern, central and southeastern Iran) and R3 (southern Iran). R1 exhibited the highest frequency and intensity of WEPEs, while event duration contributed comparably across R1 and R3, reaching up to 500-h/25-year (∼21-day/25-year). Composite analyses reveal that WEPEs over R1, R2 and R3 are associated with upper deep trough over Red Sea, eastern Saudi Arabia, and the Red Sea extending toward central Saudi Arabia, respectively. Increased instability and dynamical forcing substantially strengthen upwards motion, while moisture transport is dominated by strong integrated vapor transport from the Red Sea and the Persian Gulf. Lead-lag composite analysis of 200 hPa geopotential height anomalies reveal a clear synoptic evolution preceding WEPEs across Iran. Furthermore, WEPEs over Iran is closely associated with Circumglobal Wave Train (CGT) in both seasons, with North Atlantic Oscillation (NAO) influence WEPEs indirectly by modulating CGT variability.

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hal-05593717 , version 1 (16-04-2026)

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Elham Ghasemifar, Irfan Ur Rashid, Céline Planche, Jean-Luc Baray, Mansour Almazroui, et al.. Widespread extreme precipitation events over Iran: Large-scale patterns and their associated global indices. Atmospheric Research, 2026, 337, pp.108937. ⟨10.1016/j.atmosres.2026.108937⟩. ⟨hal-05593717⟩
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