Climatology of atmospheric rivers in the Asian monsoon region

Abstract

The climatology of atmospheric rivers (ARs) and their roles on precipitation extremes have been extensively researched over western North America and Europe, yet ARs in Asia, especially for those affecting the densely populated countries including Bangladesh, China, India, Thailand and Vietnam are not adequately understood. Here, the climatological characteristics of landfalling ARs, including their frequency and intensity, in the Asian monsoon region for the period 1979-2017 are investigated using the ECMWF ERA-Interim reanalysis dataset. The inter-annual variability of landfalling ARs associated with the combination of the El Niño-Southern Oscillation (ENSO) and the Quasi-Biennial Oscillation (QBO) is presented. The results suggest frequent AR activities over southern India, Indochina Peninsula, southern China, Korea and Japan from May to September. ARs are found to contribute up to 44% of the total summer precipitation over the coastal regions of East Asia and up to 36% in South Asia. Also, ARs are associated with up to 68% of the summer extreme precipitation amount in East Asia and 52-56% in South Asia. The connection between ARs and extreme precipitation is partly explained by the increased precipitation efficiency when ARs occur, indicating a stronger ability of the atmospheric dynamical factors to deplete moisture and generate strong precipitation. The analyses of the combined ENSO-QBO effects on ARs show that ARs in the subtropics tend to become less frequent in the years preceded by an El Niño event due to the weakening of the low-level monsoonal flows associated with the weakened land-sea thermal contrast and upper-level tropical easterly jet, and such modulations tend to become more significant under the easterly phase of QBO.

Impacts of moisture supply from the subtropical western Pacific on the subtropical high and the atmospheric river during the heavy rain of 2020 in Japan

“…Particularly, it has been demonstrated that most extreme events during the Meiyu-Baiu season could be related to the strong moisture transport with narrow, filamentary shapes, i.e., the atmospheric rivers (AR, e.g., Kamae et al, 2017;Takemura et al, 2019;Imada et al, 2020). For example, Liang and Yong (2021) argued the contributions of ARs to total precipitation in East Asia and suggested ARs could be associated with 68% of the summer extreme precipitation in East Asia. Similarly, Park et al (2021) also showed that ARs may contribute to 60%-80% of heavy rainfalls in East Asia from June to July.…”

Distinct Features of Atmospheric Rivers in the Early Versus Late East Asian Summer Monsoon and Their Impacts on Monsoon Rainfall

“…However, ARs are also frequently observed away from the main storm track regions, determining local extreme events. Such examples include ARs in the central and southeastern U.S. (Debbage et al., 2017; Lavers & Villarini, 2013a, 2013b, 2015; Mahoney et al., 2016; Nayak & Villarini, 2017), the Mediterranean Sea (Lorente‐Plazas et al., 2020) and the Asian monsoon region (Liang & Yong, 2020; Pan & Lu, 2019) including East Asia (Kamae, Mei, & Xei et al., 2017; Kamae, Mei, Xie, Naoi, & Ueda, 2017; Kim et al., 2021; Pan & Lu, 2020; Tsuji & Takayabu, 2019). These studies suggest that the underlying dynamics of ARs can be diverse from region to region.…”

Characterising the interaction of tropical and extratropical air masses controlling East Asian summer monsoon progression using a novel frontal detection approach

“…The identification of areas with high values of moisture content and transport has a primary role in this study. Integrated vapour transport, IVT hereafter, is widely used to identify atmospheric rivers and more generally regions of enhanced moisture transport (Dacre et al, 2015;Rutz et al, 2014), also over the EASM region (Liang and Yong, 2020). Here, IVT is defined as…”