[A-AS08] General Meteorology

[AAS08-P11] Relationship between large-scale atmospheric conditions and western North Pacific tropical cyclones in 2019: large-member ensemble simulation

*Tomoe Nasuno^1,3, Misaki Hishinuma^2,1, Yohei Yamada¹, Masuo Nakano^1,3, Chihiro Kodama^1,3, Fudeyasu Hironori^2,3 (1.Japan Agency for Marine-Earth Science and Technology, 2.Yokohama National University, 3.Typhoon Science and Technology Research Center, Yokohama National University)

Keywords:Tropical Cyclones, large member ensemble simulation, large-scale atmospheric environment, boreal summer in 2019

Tropical cyclones (TCs) are not totally passive to the large-scale environment but interact with it. TCs sometimes remotely affect the moisture fields and precipitation, known as pre-typhoon rainfalls (PRE). TCs also modulate the location and strength of the North Pacific subtropical high (NPSH), which can affect the path and translation speed of TC themselves. Correct estimation of these modifications is beneficial for disaster prevention, as well as for possible weather modification. On the other hand, TCs tend to generate successively and the interactions also depend on their locations and intensity. In this study, we focus on the TC intensity and aim to understand its relationship with the moisture and dynamical fields in the western North Pacific (WNP) by case study of 2019 late summer.
In early September 2019, typhoon Lingling were formed in the over East China Sea and south of Japan, respectively. Faxai was a compact and strong TC and hit Japan on 9 September. Taking an advantage of large-scale ensemble simulation using a global nonhydrostatic model which marginally resolves TCs (Yamada et al. GRL, 2023), we examined the correlation between the intensity of simulated Faxai (when it passed over Tokyo) and the large-scale fields. Positive correlation between the Intensity of Faxai and the moisture to the east of Hokkaido during two-day period prior to the Faxai’s approach, implying remote effects of TC on the moistening there. Composite map of the lower tropospheric flow fields and moisture for strong TC cases show that when Faxai is strong the adjacent part of the NPSH is strengthened and intense southerly is formed between Faxai and the NPSH, which is connected to the moistening to the east of Hokkaido. For the weak TC cases, in contrast, the lower tropospheric flow is oriented more northwestward over the central Japan between large-scale negative (positive) height anomalies to the west (east), with Lingling-like low pressure system embedded in the western part. The lower tropospheric flow is connected to WNP (east of Philippines) for the strong TCs, while it is connected to monsoon westerly over southeast Asia for the intense TCs. These suggest systematic relationship among the relative intensity of TCs and the major moisture path.