In Kanto area, Japan, the towering cumuli and cumulonimbi are often observed in a clear day of summer over Boso and Izu peninsulas, while over Miura peninsula such cumuli are never observed. In this study it was tried to investigate numerically the effects of peninsular width and thermal condition on the sea-breeze over a peninsula, using a two-dimensional model in the vertical plane.
Some interesting results are summarized as follows: (1) The strong ascending flow appears at the center of a peninsula in the evening, and is weakened rapidly corresponding with the increase of the peninsular width. (2) There is the peninsular width of about 30-50 km where the most preferable vertical velocity is observed, and the velocity reaches three times greater than that for the so-called sea-breeze. This width is equivalent to those of Boso and Izu peninsulas. (3) In the case of the large width crossing over 150km, the strong vertical motion such as stated in (1) disappears excepting that for the sea-breeze circulation which develops in daytime.