The present paper treats in detail the difference in mechanical structure between the two lines of discontinuity which appeared one after another, one extending from north to south and the other from west to east, with special care to point out the contrast between the weather conditions accompanying them and to make clear their effects upon the development of cyclones. The principal results thus obtained are as follows: 1. In general, depressions on a line of discontinuity from north to south develop remarkably, and the bad weather accompanying them passes quickly. 2. When there exists a trough of low pressure from north to south, a frontal zone with the temperature gradient from southeast to northwest is produced and gives abundant vorticity to depressions along the trough. As these depressions grow vigorous, warm and cold air-masses are drawn towards the center of depression from remote places. Thus the temperature gradient of the frontal zone where the cyclonic vorticity is prevailing becomes greater and greater, until the frontal zone soon converts into a remarkable front exhibiting the so-called “animate growth” of depression by taking foods from the surrounding field. 3. In Japan and her neighbourhood, the warm front whose intensity increases with the deepening of the center of cyclone is also much affected and sharpened by the topography of Japan proper. The cyclone does not move with the air of the warm sector as in Europe, but rather along the warm front (it was formerly called a steering line) which in general extends to eastnortheast or northeast from the center. At the warm front, southerly (warm) and northerly (cold) currents converge and heavy rain falls there. 4. As the depressions develop, the cold front becomes also more remarkable. 5. Depressions on a line of discontinuity extending from west to east do not develop in general, and owing to its slow motion gloomy weather continues for several days. 6. In the above case, the high pressure on the northern side of the line of discontinuity enlarges its area of influence eastwards, pushing away the warm front southwards, therefore the warm front turns out to be a cold one and the cyclonic vorticity decreases. 7. When warm air becomes fresh in the frontal zone, a depression is liable to form there. In an unstable field where the pressure gradient is small, a depression is easily formed even in a single air-mass by a slight discontinuity of the wind direction or air temperature which can be produced by a small difference between the paths of air-masses branched off from the same origin. 8. When a line of discontinuity extends from west to east, the field is nearly barotropic. But when it extends from south to north, the field is baroclinic and cyclogenetic, the direction of pressure gradient being from west to east and that of temperature gradient from southeast to northwest. In the latter case a depression necessarily develops. 9. In front of a depre sion on the line of discontinuity extending from south to north, the direction of isothermal lines is divergent, but in the rear convergent. On the other hand, in front of a depression on the line lying from east to west the cold northeasterly air currents prevail, hence the result is completely opposite to that of the former case. Consequently the present argument agrees partly with Scherhag's divergent theory, and partly with Sutcliffe's theory of geostrophic departure.
This memoir is essentially a sequel to one which we recently published in this journal with the title “Cosmic-Ray Intensities and Air Masses”. The determination of the influence of cold and warm fronts on cosmic-ray intensities, using the materials during the period 1937-1939, constitutes the main subject of discussions in the present paper. The cosmic-ray intensity (after reduction to the normal pressure) is almost constant in general, within the accuracy of observation at least, on the passage of individual cold fronts (the intensity increases 0.12% in mean on 8 representative cold-front passages), but it decidedly decreases on the passage of marked warm fronts. Fig. 2 illustrates a remarkable warm front from which heavy rainfalls resulted over Kwantô District during the period, June 28-July 5, 1938(1). It is well known that in our latitudes a warm southerly current of great depth accompanied with the passage of warm front might extend upwards to a height of 10 or 15km without losing its intensity, while a cold northerly current is shallow and seldom exceeds some 3km of height. It is therefore obvious from these data that the depth of cold or warm air would bring pronounced varieties in the cosmicray intensities. The distribution of cosmic-ray intensities in the area of migratory thunder is shown in Fig. 3, which illustrates the structure of thunder of cold-front type.
Using the results of cosmic-ray observations made at the Institute of Physical and Chemical Research in Tokyo, cosmic-ray intensities in different quadrants of typhoon are studied. The conclusions stated below are based on the examination of a number of similar examples which are not reproduced here. As regards the upper air structure in the north quadrant of typhoon, the nature is quite the same with that of an ordinary extratropical cyclone. For example, a tropical disturbance appeared on September 11, 1939, in the southern sea far away from Japan proper. The center crossed the sea to the southeast of Tokyo on September 23. Later, on October 2, 1939, a typhoon crossed the sea to the southeast of Tokyo, following a path quite similar to the former one. The tracks are shown in Fig. 1, in which the thick full lines represent the observed paths of two typhoons and the attached marks give the morning positions of the centres respectively. In Fig. 2 are given the observed cosmic-ray intensities in Tokyo during the passages of typhoons. The materials observed show that the cosmic-ray intensities are fairly constant during the period.In the south quadrant of a typhoon fresh tropical air advances rapidly to the north under the influence of the typhoon. On September 11, 1937, a typhoon crossed the Sea of Japan northeastwards, the track being shown in Fig. 3. The cosmic-ray materials on that day illustrated in Fig. 4 show that the intensity decreased beyond doubt during the passage of the typhoon, though the intensities at the stage of full violence of typhoon were unfortunately uncertain. Comparing Fig. 2 with Fig. 4, the cosmic-ray variations in the typhoon area are quite in accord with the facts which are obtained by aerological observations in the typhoon area(1); and such cosmic-ray variations can be safely attributed to the “Temperature Effects”. The distributions of cosmic-ray intensities in cyclonic and anticyclonic areas are shown in Figs. 5 and 6 in their revised forms after elliminating the seasonal variation of the paths of barometric centres.
The distribution of air temperature in January and August, in Tokyo and its neighbourhood, was investigated local-climatically, by using the results of observations made at 36 stations which are in the northern part of Kanagawa, the southern part of Saitama, the south-western part of Ibaraki and the north-western part of Tiba. The main results are as follows: a. The range of temperature is smaller in the vicinity of seashore and rivers, in industrial regions and in the eastern part of mountainous regions of Kwanto, and larger over the terrace in the western suburbs of Yokyo. b. In the region around Tokorozawa, the mean maximum temperature in the daytime is almost equal to that in the center of Tokyo City, but on the contrary, the mean minimum temperature is much lower.
In this short note, some relations between the daily means of vapour tension and air temperature in Tokyo are studied. Assuming that the temperature T is expressed by T=ax+by+cz+dm+N, where x, y, z and m are the mean vapour tension, the total solar and sky radiations measured by Robitzsch-actinograph, the hours of sunshine, the mean amount of cloud in the night-time respectively and N is a certain constant, we have calculated the coeffcients a, b, c, d, Nfor every month by the method of least square. The result of this calculation shows that a varies with the vapour tension, the annual mean of a being 1._??_32/m. m; the annual mean of T-N is 17._??_3C. It seems that a decreases as vapour tension increases. The annual means of and are about 62%, 23%, 8% and 7% respectively. The above results show that there is an intimate relation between air temperature and vapour tension, and that the radiation income can not also be neglected for forecasting the air temperature.
The amount of evaporation from evaporimeters was compared under various conditions of the ground and it was found that the amount of evaporation depends on the condition of the ground. For example, an evaporimeter on a wooden board evaporates about 20% larger amount of water, than that on lawn grass. Such a difference seems to be explained by the difference in temperature of water due to the conduction of heat from the ground.
Recently, the present author introduced a new idea on the horizontal stability of the atmosphere, after Helmholtz's theory on air mass ring. This is mathematically given by the formula: Applying the above equation, the author calculated the magnitude of pressure anomaly possible on the rotating earth, which is Thus it may be concluded that the maximum pressure anomaly is possible at latitude 45°. Its magnitude may be estimated as 0.51mmHg/1000m.