The use of the geostrophic approximation gives rise to inertio-gravitational oscillations which are meteorologically unimportant “noise” disturbances. In the first part of this paper, the physical explanations about the occurrence of those inertio-gravitation oscillations are given in the case of barotropic atmosphere. In the latter part of this paper, the general method for filtering out the “noise” in the three-dimensional atmosphere is proposed. Such a treatment is discussed by introducing G-number which is the ratio of the velocity potential χ to the stream function φ. This G-number simplifies the equations we are concerned with and also the associated discussions. The quasi-geostrophic equations hitherto used correspond to those of zero order of G-number.
Using the non-dimensional barotropic vorticity equation, various aspects of barotropic disturbances are investigated. First we obtained the criterion for similarity of two kinds of barotropic motions, and compared with two wave systems, one has characteristic quantities of the disturbances in the actual atmosphere and the other has those in a model tank. Second, general nature of the pattern of the disturbance is discussed by expanding the non-dimensional stream function in the power series of non-dimensional time. The timely change of the kinetic energy is also treated similarly. Third, general characters of disturbances in a closed zonal belt is discussed. Fourth, to make the general discussion on the disturbances in a closed zonal belt concretely, a simple disturbance in a jet-like zonal basic flow which was similar type was treated by Kuo. Expanding all quantities in power series of non-dimensional time, the velocity and energy of the mean zonal flow are calculated up to the terms of fourth derivative. The increase or decrease of the kinetic energy of the disturbance is investigated also up to the fourth derivative of time. The change in the profile of the mean zonal flow is also treated.
Using an interative method, the stream lines in two typical cases, i.e. a cyclonic and an anticyclonic 500-mb flow patterns are obtained from the balance equation. It is shown that the patterns of stream lines are very similar to those of height contours, but significant differences appear near the centre of cyclone. Wind speeds which correspond to the stream lines thus calculated give better coincidence with the observed ones than the geostrophic wind speeds. This improvement is explained chiefly by the concept of gradient wind. Further the integral form of the balance equation is obtained, and it is shown that the departure of the stream lines from the height contours is due to the effects of vorticity and kinetic energy.
A microbarographic observation at three points near Shionomisaki was carried out, to obtain data of the microbarographic waves available for testing the modern various theories of the waves. Three available examples obtained by this project were, together with a classical example by Ali and recent four ones by Munk and Gossard, submitted for the test It may be concluded that almost all the observed microbarographic waves belong to the stable type and not to the unstable one, from the fact that almost all the observed data satisfy the frequency equation. We could not draw any definite conclusion to judge the various theories of predominancy of the waves.
The microbarographic waves recorded by three-point simultaneous observations near Shionomisaki for two years are statistically investigated from various standpoints, taking account of the upper-air data and the natures of the wave propagation.
An example of a high-level cyclone to the south of the maximum westerlies, with its entire life within the network of aerological observations of the Far East, is investigated. The conditions for the formation of such a high-level cyclone are found firstly to be a rapid intrusion, of cold air into the upper westerlies from the north and to lie in the dynamic instability of the upper tropospheric westerlies. The observational occurrence of negative absolute vorticity south of pronounced jet streams, in connection with the cutting-off process of a low, is illustrated in the cross section and is reasoned by aa perceptible influence of the vertical motion in changing the vorticity about the vertical. It is also presented in terms of the height profiles of selected isobaric surface that in that case the upper low does not extend down to the lower level. The westerly displacement of the high-level cyclone is mainly dependent on the easterlies prevailing over the Japanese Islands above the level of the tropical tropopause. The thermal structure is studied in the vertical west-east cross section through the center of high-level cyclone. The outstanding example is the formation of an isolated island of warm air below the tropical tropopause through the descent over a cold cyclonic vortex. A new “false” tropopause is seen to form as the lower limit of such descent.
The transformation of the cP air mass into the mP air mass due to upward heat and moisture supplies from the warmer sea surface around Japan is investigated. Keeping aloof from treating the transfer processes theoretically, available measured data are utilized for evaluating the modification processes and constructing a lower atmospheric cross section following the air column throughout the whole modified layers. The results are almost the same as those of former investigations1) obtained theoretically with little addition to be made. But this report will serve to verify those result with the actually observed informations and to present some simple clue to the forecasting of the cloud and the snowfall.
It has been indicated that the occurrence of cold of hot summer over the nothern Japan is closely connected with prosperity and decline of the oceanic circulations in Tohoku sea region (Oyashio). On the other hand, it is also a well-known fact that the intensity of Oyashio is reenf orced by sea-ice on Okhotsk Sea. The author adopted the drift-ice periods at Abashiri and Shana by using a index on the Sea-ice intensity in Okhotsk Sea, and the annual deviations in drift-ice periods on both places are divided into five types for the sake of convenience. From the significance test of differences between sample and population probability on each types, it became clear that cold-summer comparatively easy to occurs after SO-type (see Table 1) or L2-types in its year (level of significance 25%), and hot-summer hard to occur after SO type by experience, etc. The detail of the methods of concrete statistical forecast on Sea-ice will be given in the next report.