Numerical Simulation for the Topographical Effect on the Sea-Land Breeze in the Kyushu Island

Abstract

The sea and land breezes in the northern region of Kyushu Island in Japan under the condition of no synoptic wind in typical summer season are simulated by a three dimensional numerical model.This study provides an evaluation of the diversification of the local circulation owing to the topography, e. g. irregular seashore lines and mountainous topographies.In order to investigate the influence of mountainous topography on the local circulation in Kyushu, we compared the case of the realistic ground elevation with that of the flat in the northwestern region of Kyushu which is characterized by the irregular coastal lines, the comparative flat topography and dispersive mountains.Further we also compared them with the case of the realistic topography in the north-eastern region of Kyushu which has the monotonus seashores and the spread mountain areas.In the northern region of Kyushu, the irregular coastal lines (esp. topography of peninsula) produce characteristic local circulations and variation of winds in connection with mountainous topographies.The mountainous topographical effects are summarized; (1) the upward vertical winds concentrate above the mountain area in the day time (down slope wind in the night), (2) the horizontal winds are oriented by the valley (e. g. in the sea area surrounded by a mountainous topography) and (3) the winds are enforced in the area of converged mountainous topography.The sea breezes in the small islands near the Kyushu are strongly affected by that in Kyushu.Further the penetration of sea breeze to inland or other area is effective factor on the diurnal wind variation at any place (esp, in the western region).

Diurnal Variations in Summertime Surface Wind upon Japanese Plains: Hodograph Rotation and Its Dynamics

“…The authors considered two different forces in a horizontal plane, and showed that anticlockwise rotation could occur in the case of a phase difference between the forces. The two forces might correspond to a sea breeze system and a larger-scale flow effect (Fisher 1960;Itoh 1983Itoh , 1989Prezerakos 1986;Helmis et al 1995;Simpson 1996), or a land−sea pressure gradient force and a topographically induced pressure gradient force (Mass 1982;Ookouchi and Wakata 1984;Orlic et al 1988;Steyn and Kallos 1992;Simpson 1996;Bastin et al 2005;Nitis et al 2005).…”

Numerical Experiments on the Interaction of Ocean and Bay Breezes

“…The model used in this study is almost the same as the model of Ookouchi and Wakata (1984). As well as for the atmosphere, temperatures for the ground surface and the soil are calculated using the surface energy balance and soil temperature equations.…”

Winter Land and Sea Breezes in the Sagami Plain;

“…In recent years numerical modeling of land and sea breezes have incorporated some topographic effects. Examples are given by Kikuchi et al (1981) and Ookouchi and Wakata (1984). In both of the above papers it was shown that the wind system was strongly influenced by the surrounding mountain topography.…”