Record-Breaking Northward Shift of the Western North Pacific Subtropical High in July 2018

Abstract

The northward shift of the Western North Pacific Subtropical High (WNPSH) in July 2018 broke the historical record since 1958 and resulted in extreme heat waves and casualties across Northeast Asia (NEA). In the present work, we associated this extreme WNPSH anomaly with the anomalies of barotropic anticyclone above NEA originating from the strongest positive tripole pattern of sea surface temperature anomaly (SSTA) in the North Atlantic in July. Both data analysis and numerical experiments indicated that the positive tripole SSTA pattern could produce an upper-tropospheric wave source over Europe, which stimulated an eastward propagating wave train along the subpolar westerly jet over the Eurasian Continent. When its anticyclonic node reached NEA, the WNPSH started to shift northward. After the cyclonic node in the circulation anomaly encountered the Tibetan Plateau (TP), atmospheric diabatic heating was enhanced over the eastern TP, initiating another subtropical wave train, which furthered the northward shift of the WNPSH. Therefore, the wave source over Europe was critical for the northward shift of the WNPSH in July, connecting the tripole SSTA pattern in the North Atlantic with the WNPSH anomaly and maintaining the downstream effects of thermal forcing over the eastern TP on the East Asian summer monsoon.

Impacts of Seasonal Transitions of ENSO on Atmospheric River Activity over East Asia

“…As an example, variability in the Atlantic SST possibly affects East Asian atmospheric circulation via changing tropical atmospheric circulation (e.g Li et al 2016;. Kamae et al 2017d) or mid-latitude circulation pattern (e.g Liu et al 2019)…”

Anthropogenic Influences on the Persistent Night-Time Heat Wave in Summer 2018 over Northeast China

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What Caused the Extraordinarily Hot 2018 Summer in Korea?

“…Shimpo et al (2019) stated that 2018 rain event terminated early with the northward shift of the stationary Baiu front due to re-enhancement of the North Pacific subtropical high. Liu et al (2019a) mentioned that the northward shift of the North Pacific high is record-breaking in 2018 since 1958. In the model experiment studies related to the 2018 HWs, Imada et al (2019), based on the results of a large-ensemble simulation, argued that the extremely high temperatures over Japan in July would not have occurred without anthropogenic global warming.…”