On the Prediction of Rain for the Oosaka Districe (The 1st Paper)

[摘要] This report consists essentially of two parts, the one treats of the upper currents in layers of 1000m. and 2000m. above the ground of the city of Oosaka in about twelve hours before the beginning of rain, and the other is intended to find out characteristics of the pressure distribution and of its change in a day before raining.Some results obtained by this investigation are as follows, and may be useful for the daily weather forecasting of the district.(1) SSW-erly currents prevail exceedingly in the 1000m. layer above the district during a whole day long before rainy day, while the most prevailing current is WNW-erly in the same layer if we take a mean in a year. The frequency of S, SSW, SW and WSW-erly wind attains as much as 70%. In the case of the 2000m. layer, the tendency of the wind direction is generally the same.(2) There are 6 types of pressure distributions under which the weather tends bad in this district. In those days of the above types (excepting one) the wind direction gradually changes with inercasing height clockweisely from NE to SW and in the layer of 1000 or 2000m. SW-erly wind prevails in almost all cases.(3) Let p1, p2, p3 be the pressure at the same time at S_??_isyûtô, Oosaka, Niigata respectively and putK≡(p1-p2)+2(p2-p3)=(p1-p2)-2p3, C≡(dp1/dt-dp2/dt)+2(dp2/dt-dp3/dt)=dK/dtthen the weather of next day at Oosaka may be conjectured by the relation between K, C. It is usually fair at Oosaka when K is greater than the mean value and in the other case it becomes bad and even the rainfall comes unexpectedly in case of both quantities K and C become negative.It is, however, inconvenient to use above results as they fail sometimes when the pressure distribution changes rapidly due to the approaching of cyclones.

[学科分类] 大气科学