Synoptic and large-scale drivers of extreme precipitation events in the Himalayas

Bharati, P., Deb, P. and Hunt, K. ORCID: https://orcid.org/0000-0003-1480-3755 (2026) Synoptic and large-scale drivers of extreme precipitation events in the Himalayas. Quarterly Journal of the Royal Meteorological Society. ISSN 1477-870X (In Press)

Abstract/Summary

Extreme precipitation events (EPEs) in the Western Himalayas (WH) have significant cross-sector impacts, yet understanding of their seasonal characteristics and synoptic drivers remains inadequate. This study presents an analysis of EPEs across the full annual cycle of the Himalayas from 1979 to 2023, identifying their spatial and seasonal distributions and associated precursor weather regimes. Based on the frequency of seasonal EPEs, the Himalayas are categorized into winter-dominated (Karakoram, WH, and northwest Central Himalaya (CH)) and summer-dominated (CH to Eastern Himalaya). By clustering circulation fields during EPEs, six dominant weather regimes are identified: four monsoon-driven (Bay of Bengal-low pressure system [BoB-LPS], Arabian Sea-LPS [AS-LPS], Monsoon-Break, and Western Disturbance-Monsoon [WD-Monsoon]) and two winter-driven (WH-WD and CH-WD). Each regime exhibits a distinct atmospheric circulation pattern. The BoB-LPS and AS-LPS regimes are characterized by quasi-stationary blocking by an anomalous upper-level anticyclone situated over the WH along with the LPS formed over the BoB and AS, respectively. The Monsoon-Break cluster reflects a weakened monsoon trough and suppressed convection over the BoB and core monsoon regions. In contrast, the WH-WD and CH-WD clusters are associated with upper-level cyclonic anomalies characteristic of WDs, embedded within broader wave-train-like circulation anomalies that are consistent with previously reported NAO–STJ–WD pathways. There is a spatial dipole in composite precipitation: EPEs in monsoon-driven clusters are associated with anomalous moisture transport from the BoB and AS, which results in dry conditions in the winter-dominated Himalaya, while EPEs in WD-driven regimes result from anomalous westerly moisture flow from the AS and associated dry conditions in the summer-dominated Himalaya. This study offers a synoptic-scale framework for interpreting the circulation regimes associated with Himalayan EPEs and for identifying conditions that may be favourable for their occurrence.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/131440
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > NCAS Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Royal Meteorological Society
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