Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165
Volume 15, Issue 9
Displaying 1-6 of 6 articles from this issue
• T. Hirono, K. Sakata
1937 Volume 15 Issue 9 Pages 347-353
Published: September 05, 1937
Released on J-STAGE: February 05, 2009
JOURNAL FREE ACCESS
The problem entit_??_ed is an important matter concerning with the prevention of flooding disaster in the city of Oosaka. In this paper, the present authors have investigated the problem of high waters at Oosaka and Kobe using the data obtained at the several typhoons.
First of all the high water at Oosaka was treated at the typhoon of September 1936. The treatment showed that the differnce between the predicted height of the tide and the observed height, namely the abnormal high water H caused by the violent wind and the low pressure can be expressed as follows:
or
Here V (cm/sec) is the component of wind velocity taken in the direction of the major axis of Oosaka Bay, p the observed atmospheric pressure in Hg-cm., p_??_ the normal pressure, a the appropreate constant, and c=13.2+c', p0=76.0+p_??_', 76.0-p=P, b the wind factor, and c the pressure factor.
The numerical values of wind factor b and pressure factor c are calculated as follows:
b=0.21 and c=17.15.
The theoretical value of the wind factor obtained by Dr. Colding for the case concerned is 0.17 and smaller than the value obtained above. It is probably due to the complexity of the form and depth of the bay, here overlooked.
The high water at Kobe was discussed for a severe typhoon which passed through the Oosaka bay in August 1935. Calculating as before we get;
b=0.056 c=25.4
A probable reason for the large value of c thus obtained will be the following. A kind of drift current produced, by severe wind within the typhoon area causes an abnormal high water in the ocean, and it flows into Oosaka bay and makes, the water there high.
If we assume that the inflow is constant during the time concerned, the accumulating mass should be proportional to the inflow, and a following equation may be obtained: (a+13.2p0')+bV2+c'P+dT=H-13.2P
Where T is the time concerned, d the accumlation factor. Calculating from this formula, we get b=0.015, c=19.25, d=0.57.
The pressure factor c is yet too large though it is smaller than that obtained in the previous case. But it seems to be impossible to separate the pressure effect from the accumlating mass by the drift flow, because the pressure falls almost proportionally to the time.
Assuming c=13.2 as a theoretical value, we get d=0.86, b=0.011 and again assuming the pressure factor of the same value as above, and considering the term of T2, the previous equation becomes
(a+13.2p0')+bV2+d+dT2=H-13.2P
Here we get the wind factor 0.031 and accumlation factor 0.72. This value of the wind factor coincides very well with that obtained by Colding's formula for Kobe.
Besides, assuming that the accumlation factor is 0.7, we calculated the maximum velocity of flow passing through the Kitan straits and obtained 2m/sec for velocity of flow. Though we have no data to affirm the result at present, the above velocity of inflow seems not to cause serious error as the current there.
• T. Kinka
1937 Volume 15 Issue 9 Pages 353-372
Published: September 05, 1937
Released on J-STAGE: February 05, 2009
JOURNAL FREE ACCESS
It is well-known that the following two kinds of wind prevail near the surface in the Oosaka district. The one is a NE-erly light breeze blowing parallel to the River Yodo which has an intimate relation to the generation of fog and rain in this district_??_ The other is a SW-erly swift wind blowing along the major axis of the Oosaka Bay, which is closely connected with the storm of this district.
It is important to know for the storm warning from when and where and with what strength a stormy wind blows. We first investigated in this paper statistically the time of beginning of a storm from the positions of centers of tropical cyclones, and in the second place the strength of wind from the pressure gradients there. The results thus obtained are as follows.
(1) The frequency of storm hour at Oosaka is investigated for respective direction of wind during 1895-1936 (inclusively). In this district most part of storm hours is occupied by the SW-erly wind and when the wind velocity exceeds 15m/s, SW-erly gale becomes to prevail conspicuously.
(2) When a storm begins to occur in the Oosaka district, the cyclone centers are found at the eastern side of the longitude of the Oosaka (135°E), i.e. the storm at Oosaka begins when the cyclone center comes to the northern side of Oosaka or its NE-ern quadrant; this fact may contradict to the general idea that the tropical cyclone gives the strongest storm in its SE-ern quadrant.
(3) We may sometimes experience NE-erly gales in the case of a developed cyclone approaching from the offing of Tosa coast, SW to Oosaka, but it must be mentioned that the SW-erly storm bursts out as soon as the cyclone center has arrived at the longitude-135°E.
(4) There will be the risk of the storm at Oosaka if the mean value of pressure gradient between the storm center and Oosaka becomes greater than 1 mmHg/deg. The max_??_mum wind velocity at Oosaka is apt to be greatly influenced by the steepness of gradient at the time of storm begining.
(5) For the forcasting of storm in the cold season due to the powerful anticyclone on the continent, the pressure differences between Saisyû Island and Oosaka, Oosaka and Niigata are useful. When these differences attain 6mm. and 4mm. respectively, the storms come in almost all cases.
(6) The empirical formulae of the relation between the wind velocity and the pressure gradient are obtained for the Oosaka district. These are classified into two. according to the direction of wind and applicable when the velocity is less than 15m/s.
VWSW=1.0+5.6G_??_for SW-erly wind, VNE=0.6+2.0G_??_for NE-erly wind.
where V is the velocity in m/s and G the gradient in mm/deg.
(7) A simple formula is used for the evaluation of the pressure gradient at a place by the pressure change observed there when a typhoon is approaching, which is where _??_p being the pressure change per hour, V the moving vel. (km/h) of the typhoon, and θ the angle between the direction of movement of typhoon and the line connecting the typhoon center to that place. Comparing the gradient calculated by the above method with that obtained from weather chart, the growth or decay of the typhoon can be examined.
(8) By three typhoons 1911 VI 19, 1912 IX 23, and 1934 IX 21, the relation between pressure gradient and the wind velocity is examined_??_ In this case also, the relation is quite different with each other for the two wind direction, NE-erly and S-erly. In the latter case the relation is expressed in a parabolic form in spite of linear in the former case.
(9) The distribution of wind velocity at 10m. height in the Oosaka city is approximately expressed as where V0 being the wind velocity at the mouth of the Oosaka harbour and V that of station apart by D km. from the above place.
• T. Kinka
1937 Volume 15 Issue 9 Pages 372-379
Published: September 05, 1937
Released on J-STAGE: February 05, 2009
JOURNAL FREE ACCESS
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 put
K≡(p1-p2)+2(p2-p3)=(p1-p2)-2p3,
C≡(dp1/dt-dp2/dt)+2(dp2/dt-dp3/dt)=dK/dt
then 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.
1937 Volume 15 Issue 9 Pages 380-385
Published: September 05, 1937
Released on J-STAGE: February 05, 2009
JOURNAL FREE ACCESS
By applying Takahashi's method the present author analysed the proper oscillation of the surface layer in Tokyo. Moreover he analysed the coda X, which appears in case of the deep seated earthquake, and discussed the reflection waves from the discontinuous layer. If we assume that the seismic waves travels perpendicularly to the discontinuous layer, there should occur several reflection waves and the interval T of their waves is given by the following relation: T=2H/V where H is the depth of discontinuous layer, V the velocity of S wave. From this relation we calculated the depth of layer and obtained approximately the value as 45km and it is found that the depth of the discontinuous layer in the region of abnormal intensity seems smaller than that in the normal region. From this relation we can explain qualitatively the several characteristics of the area of abnormal intensity.
• N. Murase
1937 Volume 15 Issue 9 Pages 386-388
Published: September 05, 1937
Released on J-STAGE: February 05, 2009
JOURNAL FREE ACCESS
Applying the Laplace's formula, the author tried to study the annual variation of the upper atmospheric pressure and temperature and obtained following results;
1. The maximum amplitude of annual pressure variation occurs at a height of RT0/g i. e. about 8-9km., where T0 denotes the temperature of the earth surface.
2. The correlations between temperature and pressure at several layers are the most close at the layer RT0/g.
3. The annual mean deviation of temperature seems to increase gradually with height.
4. Excepting near the earth surface, the annual mean deviation of presssure increases up to the height RT0/g and then decreases gradually.
5. The average height of neutral surface of pressure is about 500-600m of high and 800-900m in summer and winter, and 200-300m in spring and autumn.
6. The variation of temperature has a great influence upon the change of pressure and its effect seems to become larger with height.