TSUTSUMI Jyunichiroh University of the Ryukyus, Civil and Architecture Engineering, Associate Professor, 工学部, 助教授 (60192647)
TSUKAYAMA Seikoh University of the Ryukyus, Civil and Architecture Engineering, Professor, 工学部, 教授 (50044996)
|Budget Amount *help
¥5,200,000 (Direct Cost : ¥5,200,000)
Fiscal Year 1998 : ¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1997 : ¥3,100,000 (Direct Cost : ¥3,100,000)
The concentration of wind-borne sea-salt in the atmosphere, the amount of rainfall and the concentration of sea-salt contained in the rain during typhoons were investigated in this research project and the following general results were obtained.
1) The amount of sea-salt carried inland by a squall was found to be almost equal to that carried directly by storm sea winds. As the distance inland from the coast increased, the amount of wind-borne sea-salt decreased exponentially at any given height above ground level. In contrast to this, the quantity of sea-salt carried by a squall remained relatively stable, even as the landward distance increased. For any given period of rainfall during a typhoon, the concentration of sea-salt contained in the rainfall in its initial period is over ten times the quantity of that in its middle period, which is about ten times the quantity contained in rainfall on a cold/warm front.
2) In weather forecasting, concerning wind and sea-salt mass, an accurate
typhoon model is essential. In order to create an accurate typhoon model, accurate wind data should be taken from over a wide area, both horizontally and vertically. A new prediction model of a typhoon wind field has been proposed, based on data obtained from the successful observation of an ultra-typhoon.
3) It is believed that the vapor quantity in the atmosphere above the sea in the surf-zone exceeds the quantity given off by tropical forests. In this research project, evidence of this was produced quantitatively. This cannot hitherto be confirmed, however, due to a lack of measured data. The observed data shows that the diffusion of vapor supplied by wind-blown seawater spray from the surf zone is limited in the region of the surface boundary layer. The quantity of the sea-salt contained in the atmosphere decreases as the landward distance from the shore increases. This is due to the filter effect of the vegetation, generally forest and sugar cane, which can reach a height of up to 10m, and acts as a windbreak. In contrast to this, the quantity of vapor actually increases. This is explained as follows. As the seawater spray, produced by the breaking waves, is blown inland, it accumulates on the vegetation. These accumulated drops of seawater spray evaporate and vapor is released into the atmosphere. The grains of sea-salt, however, remain attached to the leaves. As a result, the sea-salt contained in the atmosphere over the region of vegetation decreases. Less