- 著者
- Akira T. Noda Hiroshi Niino
- 出版者
- Meteorological Society of Japan
- 雑誌
- SOLA (ISSN:13496476)
- 巻号頁・発行日
- vol.1, pp.5-8, 2005 (Released:2005-01-25)
- 参考文献数
- 17
- 被引用文献数
- 9 13
A major tornado spawned by a supercell is reproduced by a fine-resolution three-dimensional numerical simulation, and its genesis mechanism and structure are clarified. The tornado, which is associated with a maximum vertical vorticity of 0.85 s-1 and a pressure drop of 27 hPa, originates from one of the small-scale vortices on the gust front that forms between a warm moist environmental air and a rain-cooled air produced by the storm. Only the small-scale vortex that develops into a major tornado is located right under the low-level updraft associated with the low-level mesocyclone; the others that fail to develop are not. Several interesting previously-unexamined characteristics of the threedimensional structure of the simulated tornado vortex are also reported.
- 著者
- Yasumitsu Maejima Keita Iga Hiroshi Niino
- 出版者
- Meteorological Society of Japan
- 雑誌
- SOLA (ISSN:13496476)
- 巻号頁・発行日
- vol.2, pp.80-83, 2006 (Released:2006-06-29)
- 参考文献数
- 10
- 被引用文献数
- 2
Upper-tropospheric vortices having a horizontal wavelength of 300-400 km were observed on water vapor images of the Japanese geostationary satellite (MTSAT-1). Grid point values predicted by the Regional Spectral Model of the Japan Meteorological Agency show that the vortices were located along a zonal belt with strong cyclonic shear and horizontal convergence. A quasi-geostrophic linear stability analysis of the basic flow having horizontal and vertical shear shows that the fastest growing mode has a horizontal wavelength, a phase speed and a growth rate that reasonably agree with those of the satellite observation. The amplitude of the fastest growing mode is confined to a region having a meridional width of 2 degrees and a vertical depth of 2 km. An energy budget analysis shows that barotropic instability is the dominant generation mechanism for the growing mode.
- 著者
- Wataru Mashiko Hiroshi Niino
- 出版者
- Meteorological Society of Japan
- 雑誌
- SOLA (ISSN:13496476)
- 巻号頁・発行日
- vol.13, pp.135-139, 2017 (Released:2017-07-31)
- 参考文献数
- 26
- 被引用文献数
- 5
A super high-resolution simulation of the 6 May 2012 Tsukuba supercell tornado with a horizontal grid spacing of 10 m is conducted to investigate its fine-scale structure under realistic environmental conditions including surface friction. The simulated tornado repeatedly exhibits evolutions from one-cell to two-cell vortex, and subsequently to a multiple-vortex structure, where the vortex structure is sensitive to a swirl ratio. Subvortices in the multiple-vortex structure are located on the immediate inside of the radius of the maximum tangential wind speed, and cyclonically rotate around the tornado center with a slower speed less than half of the maximum tangential wind speed. The subvortices have a feature of a suction vortex accompanied by strong horizontal convergence and strong updraft near the surface. Although a superposition of the swirling winds associated with the subvortices and the parent tornado vortex causes locally intensified winds, the maximum horizontal and upward winds over the tornado's lifetime occur at the stage of shrinking of the vortex radius right before a transition to a multiple-vortex structure.