Hiroki Tsuji 교수

Precipitation characteristics and their environments are compared between two heavy rainfall events affecting the Northern Kyushu area in Japan: the July 2018 heavy rainfall event (2018 case) and the 2017 Northern Kyushu rainfall event (2017 case). Both events occurred in the later stage of the Baiu season, after the passage of a tropical cyclone, to the south of a subtropical jet, and on the front side of an upper tropospheric trough. However, contrasting precipitation properties and environmen

Abstract The role of vertically integrated water vapor flux convergence (IVFC) in heavy rainfall events in western Japan is investigated by dividing the atmosphere into a boundary layer and free troposphere using the Japan Meteorological Agency's mesoscale gridded analysis product and reanalysis product. Rainfall events are defined by peaks of area‐averaged precipitation. The results show an increase in the free‐tropospheric IVFC more than 15 h before rainfall events, contributing to atmosphere

Abstract A significant enhancement of precipitation can result from the interplay between two independent, large-scale phenomena: an atmospheric river (AR) and a cutoff low. An AR is a long, narrow region with a deep moist layer. A cutoff low is an upper-level cyclonic eddy isolated from the meandering upper-level westerly jet. Herein, we construct composites of cutoff lows both close to an AR (AR-close category) and distant from an AR (AR-distant category) over a 14-yr period across the western

To understand the basic mechanism governing the size evolution of tropical cyclones (TCs), we systematically perform numerical experiments using the primitive equation system on an f-plane. A simplified, TC-like vortex is initially given and an external forcing mimicking cumulus heating is applied to an annular region at a prescribed distance from the vortex center. Moist process and surface friction are excluded for simplification. We focus on the sensitivity of size evolution to the location o

Flicker noise suppression of K-Band scaled-CMOS VCO using striped inductors have been studied. The phase noise degradation is a problem of high-frequency VCO. Especially phase noise which arise from flicker noise is the most significantly in the case of using noisy scaled CMOS process. In this work, we present flicker noise contribution phase noise improvement using striped inductors. Striped inductors have been studied for thermal noise contribution phase noise improvement due to skin effect su

The precipitation system and environment that caused the heavy rainfall event in July 2020 over Kyushu Island, Japan, were analyzed, with a focus on a hierarchical structure. The moisture budget analysis over Kyushu revealed the contribution of the free-tropospheric moisture flux convergence moistening the atmosphere before the rainfall event. Further analyses by dividing the flux convergence into moisture advection and wind-convergence terms revealed that the moisture advection controlled the m

Abstract The relationship between the size change of tropical cyclones (TCs) and radial distribution of precipitation was investigated for TCs occuring over the western North Pacific Ocean with satellite observation data. The size of a TC is defined as the radial extent of 15 m s −1 winds (R15). The spatial distribution of precipitation was investigated by extracting two subperiods, which are the size‐increasing period and the size‐stationary period, as determined from R15 evolution. The results

Millimeter wave striped inductor VCO has been studied. To obtain lower phase noise, the enhancement of Q-factor of inductor is essential, although it is difficult in the case of dozens gigahertz region due to skin effect. In our previous results, quasi-millimeter wave striped inductor VCO can be obtained lower phase noise by suppression of skin effect. In this work, we have been investigated corner frequency of striped inductors and the phase noise of several oscillation frequencies VCO with str

<p>Recent studies indicate that precipitation systems causing heavy rainfall affecting a wide area in Japan show similar characteristics as organized precipitation systems with deep inflow layers (Hamada and Takayabu 2018; Tsuji et al. 2021). Free-tropospheric moisture is a key factor for organizing such precipitation systems (e.g., Holloway and Neelin 2009). However, less attention has been paid to the roles of free-tropospheric moisture on precipitation systems causing heavy rain