On the Effect of Topography on the Helmhotz Wave

[摘要] The influence of topography on the wave-length and the amplitude of Helmholtz wave has not, so far as I know, been discussed, so I intend here to study such a problem. H. Arakawa(2) has already studied the influence of topography on the barometric oscillation, comparing the record of micro barograph taken at Huzisan Meteorological Observatory with that of Tokyo. Following the result introduced by H. Arakawa the present author treated mathematically the effect of topography. Here a conclusion is drawn that, if the difference of the velocity and the temperature between the upper medium and the lower medium are constants, on the top of mountain range the wave length must be considerably longer, and the amplitude must be smaller than that of far distance free from the effect of topography for the stable wave, and there are some places, at which even if the wave length becomes shorter and the amplitude becomes larger than that of the places free from topographic effect the Helmholtz wave is stable, at a little a way off the summit, and the lower the surface of discontinuity is in comparison to the height of mountain range, the more remarkable such a effect becomes. In other words, the above conclusion tells us, on the top of mountain range the Helmholtz wave is difficult to appear but at some places at a distance from the summit, it is frequent to occure.

[学科分类] 大气科学