In Figure 1 are shown monthly averages of solar radiation intensity based on measurements made at several different points on the Northern Hemisphere after Herbert H. Kimball1). The monthly means or the monthly maxima of radiation for the different stations have been expressed as a percentage of their respective normals. Then for each month an average of these percentages has been computed, and smoothed by the formula (a+2b+c)/4, where b is the average percentage for the month in question, and a and c are the average percentages for the preceding and following months, respectively. The smoothed percenteges have been plotted in Figure 1, and also a free-hand curve that represents the variations in the smoothed monthly values has been drawn. The measurements show marked periods of depression in the solar radiation intensity, as follows: “(1) In 1884-86, following the eruption of Krakatoa Volcano in 1883. In 1885 the solar radiation was about 20 per cent lower than in 1883 and 1887. (2) In 1902-03, following the eruption of Pelée, Santa Maria, and Colima in 1902-with a sharp depression in solar radiation intenity at the end of 1902 by 20 per cent. (3) In 1912-13, following the eruption of Katmai Volcano in June, 1912, which caused a decrease in solar radiation in, tensity in the following month by nearly 25 per cent.” The researches of Abbot2), Humnphreys3), and others, indicate that these and earlier volcanic eruptions have been followed by a slight fall in the temperature of the earth as a whole, and especially at continental stations. Prof. T. Okada4) calls attention to the fact that these volcanic eruptions, which sent a lot of dust into the stratosphere, decreased the surface temperature in Northern Japan and caused the failures of the rice crop. The historical failures of the rice crops in Northern Japan since 1883 up to 1930 were as follows: A. D. 1884, 1902, 1906, 1913. The mean features of the failure of the crops in 1906 are quite different from, those in 1884, 1902 and 1913. After Dr. K. Suda5), there are two essential factors in the cause of cool summer, the first is the comparatively low temperature of the cold current of Oyasiwo and the sea around Northern Japan; which caused the failures of the rice crop in 1884, 1902 and 1913. The second factor, which caused the failure of the crops in 1905, is the frequent outbreaks of the polar continental air mass from Siberia to the districts in question during summer (the critical period). The historical failures of the rice crops in Northern Japan caused by the so-called first factor from 1883 to 1930, or the failures of the rice crops in 1884, 1902 and 1913 correspond strictly to the three great depressions of the curve in Fig. I. On the other hand, from 1912 to 1930, or for nearly 20 years, there were no marked volcanic eruptions of an explosive character, such as throw great quantities of dust into the atmosphere. Therefore, the upper atmospheric layers, or the stratosphere, must have been unusually clear, and, in consequence, have obstructed less of the ncoming solar radiation than usual. As a result the earth as a whole experienced a slight rise in temperature. And we fortunately had successive good harvest of rice from 1914 to 1930. Thus we can conclude that the vpriations in the measured intensity of solar radiation received at the surface of the earth are of great importanee as a meteorological factor and therefore from the forecasting point of view.
The old problems, why an almost constant lapse-rate exists in the troposphere and why exists the so-called stratosphere, are not yet solved. Nowadays, it is generally believed that these fundamental states of the earth's atmosphere can be considered as a result of radiative equilibrium. But in this paper it will be proved that these fundamental natures of the atmosphere can also be described as a dynamical equilibrium of the fluid rotating with the earti. Using the spherical polar coordinates (r, θ, ψ, ), which are independent of the earth's rotation, the state of dynamical equilibrium is described by the following three equations of motion:-- where the solutions T, P are assumed to be independent of φ, and homogeneous for all longitudes. U is the rotational flow velocity of air and its functional form is determined from the third equation. If we assume a solid rotation of the atmosphere with the earth, U becomes ωrrsin θ, ω being the angular velocity of the earth. From the remaining two equations T is solved and the so-called lapse rate of temperature is described as follows: by making use of the boundary conditions at the earth's surface: at the pole T=TP and at the equator T=TE. Using the Hann's table of TE and TP, we get the following results: For the stratosphere, to which the above discussion can be applied, we get Tropopause can be described to be discontinuousiu, temperature and continuous in pressure. The pressure distribution may be Known from equation (2), which shows low pressure at the pole and high pressure at the equator. And so the westerly and high-pressure zone of middle latitudes are not to be described as a result of the fundamental flow U. These phenomena can be explained by the second fundamental flow, which is to be considered as a deviation from U and determined from (3). Putting u=U+u, we get u∞r2sinθ•cosθ. And the pressure deviation becomes P∞rsinθ. This shows low pressure at the equator and high pressure at the pole. Thus combining two pressure systems, one resulting from the fundamental flow U and the other a deviation from this, we can understand that the so-called high pressure belt of middle latitudes is also a result of dynamical equilibrium.
§1. Introduction The so-called equations of fluid motion show that the fluid particle is accelerated by pressure gradient, which is assumed to be a force exterior to the fluid system. But, in reality, the pressure gradient is not an “exterior” force, but is influenced by the fluid motion itself. V. Bjerknes, famous theorem states that circulation is accelerated by baroclinic field. But, as mentioned just now, this statement must be supplemented by the idea that the baroclinic field may also grow as a result of circulation, because this theorem is introduced from the equations of motion. The deformation or change of pressure (temperature, etc.) field is described analytically in the following section. §2. Analysis of changing fields (Press., Temp., Pot. Temp., Density). The motion of fluid particles is analysed, and equations of the changing field of f are introduced, f being any physical quantity. That is:- and two other equations of y and z directions. This is a well-known differential formula. §3. -Equations of various changing fields. When we take density (ρ) as f, this becomes as follows by using the equation of continuity:- where_??_is the velocity vector. When the fluid undergoes polytropic change, we get for pressure (P), temperature (T) and potential temperature (θ) fields: §4. Equations of changing baroelinic fields. The baroclinic field develops as a result o fluid motion. §5. Vorticity and the baroclinic field -their growth. This problem has been discussed by many authors. But many of them treat only equations of motion. In this paragraph it is shown that these problems must be discussed by using two systems of equations, one of which is of motion, the other of changing fields. And as a result of this analysis, the following scheme of the genesis of vorticity and the baroclinic field has been obtaind for only a short time at initial growth.
The present study was carried out for the purpose of prediction of rainfall in the “Bai-u season” in Japan, based on the monthly maps of precipitation departure for the period 1913 to 1341. The results obtained are as follows: There can be seen some relation between the type of precipitation departure in February and that in June: _??_e. When February is characterized by the abundance (or scantiness) of precipitation in the southern part and its vicinity of Japan proper (Fig. 2 and 4) the amount of precipitation in the “Bai-u season ” is considerably great (or small), with the exception for the year 1926. This exception can, however, be explained from (1) the type of barometric pressure departure in February, (2) the monthly mean pressure and its gradient direction at Ogasawara in March, (3) the mean air temperature of the northern air-masses during January and February.