著者

KAWANO Tetsuya KAWAMURA Ryuichi

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-033, (Released:2020-05-12)

被引用文献数

21

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A quasi-stationary convective band that persisted for approximately ten hours caused precipitation in the northern part of Kyushu Island, Japan on 5 July 2017. The extreme amount of rainfall produced by this convective band caused a number of landslides and flash floods and resulted in a severe disaster. The Weather and Research and Forecasting (WRF) model was used to perform numerical simulations and to clarify the genesis and maintenance processes of the convective band. A full-physics WRF simulation successfully reproduced the observed features of the convective band and extreme precipitation. It is shown that a quasi-stationary convergence zone in the low level played a crucial role in generating and maintaining the convective band. Trajectory and frontogenesis analyses showed that low-level confluent flows due to the blocking effects of a high pressure system located over the Sea of Japan were responsible for the formation, intensification, and sustenance of the convergence zone. Furthermore, the frontal structure of the convergence zone was intensified due to the land-sea thermal contrast between Kyushu Island and the Tsushima Strait. Two additional experiments, namely a simulation with flattened topography of Kyushu Island and a simulation without considering raindrop evaporation also reproduced the observed band well. These results indicate that topography and a cold pool due to raindrop evaporation played only minor roles in the genesis and maintenance of the convective band.

著者

TOCHIMOTO Eigo KAWANO Tetsuya

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2017-005, (Released:2017-01-13)

被引用文献数

10

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This work investigates development processes of Baiu frontal depressions (BFDs) using a numerical model. To investigate the effects of upper-level disturbances, latent heating, and baroclinicity on the development of BFDs, case-study numerical simulations are performed. In the present study, two typical cases were selected from BFDs that appeared in June and July, 2000-2007: a BFD that developed in the western part of the Baiu frontal zone (W-BFD) from 26 to 27 June 2003 and a BFD that had formed in the eastern part of the Baiu frontal zone (E-BFD) from 1 to 3 July 2003. An available potential energy (APE) diagnosis shows that the effect of latent heating is dominant during the W-BFD development, while baroclinicity as well as latent heating is important to the E-BFD development. A sensitivity experiment excluding upper-level potential vorticity (PV) anomalies shows that upper-level disturbances are important contributors to the development of E-BFDs. The low-level PV and its production associated with latent heating suggest that the W-BFD has a development mechanism driven by latent heating. In the early developmental stage, PV near the W-BFD center is enhanced. This feature is consistent with the nonlinear conditional instability of the second kind mechanism. In the later developmental stage, PV is produced in front of the W-BFD center, in which low-level baroclinicity is large. This process is consistent with a diabatic Rossby vortex. In contrast, the E-BFD develops through a baroclinic instability-like mechanism in the moist atmosphere.