Abstract
Atmospheric rivers (ARs) that reach the complex terrain of High Mountain Asia (HMA) cause significant hydrological impacts for millions of people. While ARs are often associated with precipitation extremes and can cause floods and debris flows affecting populated communities, little is known about ARs that reach as far inland as HMA. This paper characterizes AR types and investigates dynamical mechanisms associated with the development of ARs that typically affect HMA. Combined empirical orthogonal function (cEOF) analysis using integrated water vapor transport (IVT) is applied to days where an AR reaches HMA. K-means cluster analysis applied to the first two principal components uncovered three subtypes of AR events with distinct synoptic characteristics during winter and spring months. The first subtype increases precipitation and IVT in Western HMA and is associated with a zonally oriented wave train propagating within the westerly jet waveguide. The second subtype is associated with enhanced southwesterly IVT, anomalous upper-level cyclonic circulation centered on 45^circ E, and precipitation in Northwestern HMA. The third subtype shows anomalous precipitation in Eastern HMA and southwesterly IVT across the Bay of Bengal. Interannual variations in the frequency of HMA ARs and relationships with various teleconnection patterns show that western HMA AR subtypes are sensitive to well-known remote large-scale climate factors, such as the El Niño Southern Oscillation, Arctic Oscillation, and the Siberian High. These results provide synoptic characterization of the three types of ARs that reach HMA and reveal the previously unexplored significance of their contribution to winter and spring precipitation.
Highlights
Atmospheric Rivers (ARs), a term coined in the early 1990s, describes a phenomenon that explains how baroclinic eddies transport large amounts of water vapor via relatively infrequent, long conduits of strong moisture transport across midlatitudes and into Polar Regions (Zhu and Newell 1994)
Using ERA5 reanalysis and a global Atmospheric rivers (ARs) catalog, this study revealed the climatology of ARs that reach High Mountain Asia (HMA), and their relationship with precipitation regimes in southern Asia using combined EOF analysis with k-means clustering
Western HMA ARs are associated with low geopotential heights directly north of the Arabian Sea that results in enhanced integrated water vapor transport (IVT) and increased precipitation in Western Himalayas and the Karakoram
Summary
Atmospheric Rivers (ARs), a term coined in the early 1990s, describes a phenomenon that explains how baroclinic eddies transport large amounts of water vapor via relatively infrequent, long conduits of strong moisture transport across midlatitudes and into Polar Regions (Zhu and Newell 1994). Many studies have shown the global importance of ARs to poleward moisture transport, climate, and water budgets (Zhu and Newell 1998; Guan and Waliser 2017; Paltan et al 2017; Waliser and Guan 2017; Guan et al 2018; Nash et al 2018; Ma et al 2020). Studies have shown ARs are related to precipitation extremes, flooding, seasonal snowpack, and water availability in the western United States and western Europe (Ralph et al 2006; Guan et al 2010; Dettinger 2011; Guan et al 2013; Lavers and Villarini 2013; Wick et al 2013). ARs modulate extreme precipitation and anomalous snow accumulation in many other regions including Antarctica (Gorodetskaya et al 2014; Bozkurt et al 2018; Gorodetskaya et al 2020), Australia and New Zealand (Kingston et al 2016; Ye et al 2020; Prince et al 2021; Reid et al 2021), the Arctic Ocean and Greenland
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