I am a researcher in atmospheric science at the Meteorological Research Institute (MRI) of the Japan Meteorological Agency (JMA), Japan. My research focuses on severe weather phenomena associated with extratropical cyclones, including mesoscale convective systems and tornadoes. I am particularly interested in the dynamical processes of convective storms and tornadogenesis, which I investigate using high-resolution numerical simulations and detailed diagnostic analyses. My work aims to improve the physical understanding of extreme weather events and their predictability. I have been involved in several research projects related to hazardous weather linked to mid-latitude and mesoscale systems, contributing to both fundamental research and operational meteorology. Through my research, I seek to advance storm-scale knowledge relevant to weather forecasting and disaster mitigation.
Environmental Characteristics of Recent Quasi-Stationary Linear Precipitation Systems Over Japan
In Japan, more than 50% of heavy rainfall events are produced by quasi-stationary linear convective systems (QSLPSs). Several environmental conditions are favorable for the occurrence of QSLPSs, including abundant low-level moisture inflow, high conditional instability, and moderate vertical wind shear. In this study, the environmental characteristics of recently observed QSLPSs are introduced.
Major QSLPS events are frequently observed in Kyushu and Shikoku, the southern part of Japan, during June and July, which correspond to the rainy season known as the Baiu season. During this period, warm and moist air is transported from the East China Sea and the northwestern Pacific. In early July 2020, for example, QSLPSs observed over northern Kyushu caused catastrophic damage. In this event, strong moisture transport toward Kyushu associated with mesoscale depressions along the Baiu frontal zone was an important contributor to the occurrence of the QSLPSs. An upper-level trough also contributed to the formation of these mesoscale depressions.
QSLPS events are also observed in northern Japan, although their frequency is lower than in the southern regions. For example, on 3 August 2022, a QSLPS event occurred over the Tohoku–Hokuriku region. In this case, mesoscale convergence associated with a low-level mesoscale depression contributed to the formation and maintenance of the QSLPS.
In addition, a statistical analysis was conducted to assess the utility of entraining CAPE (E-CAPE) and a simplified parameter, the KT-index. E-CAPE and the KT-index allow the effects of low- to mid-tropospheric humidity to be considered when evaluating conditional instability. A composite analysis of QSLPS events from 2009 to 2022 suggests that E-CAPE and the KT -index are useful parameters for providing more spatially confined and potentially more accurate indications of QSLPS occurrence regions. From this perspective, E-CAPE has the potential to reduce the false alarm ratio in QSLPS forecasting.