Journal of the Meteorological Society of Japan. Ser. II

The height of the origin of the anomaly of the polarization of the light scattered from the atmosphere was investigated. The polarizability was measured with two polarimeters at two sites, which are at a distance of about 20km, at the same time as possible. Parallax seems to have been found, and a reliable value of the height was calculated.

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This is a preliminary report of an experiment in a rotating dishpan with topographical barrier and no temperature gradient, to study the effect of topographical barriers on zonal currents in the atmosphere or in the ocean, in the case of no latitudinal variation of rotating velocity to verify the author's previous theoretical results.

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Some features of the instability lines which form over the Tsushima Warm Current are studied with some examples. The gust over the seas, west of KYUSYU which suddenly blows over the calm sea surface from winter to early spring causing many casualties, proved to be a thunderstorm phenomenon with an instability line.
Heavy rains in small areas in a short period of time in summer and tornadoes in every season, are also frequently accompanied by instability lines with thunderstorm. These instability lines in Japan resemble very well those in the United States of America. Some notes of instability lines in Japan are presented.

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Yin [1] has suggested that the subtropical jet stream, known to circle over the southern periphery of the Tibetan Plateau during the cool season, displaces suddenly to the north of Tibet at the last week of May. He also noted that this northward retreat of the jet stream occurs at the same time with the burst of the southwesterly monsoon over India, as well as the westward shift of the trough located over the Bay of Bengal during the cool season, and the formation of new upper trough near 70°E. Koteswaram [2] considered that the burst of the Indian monsoon occurs together with the establishment of subtropical high over Tibet, to the south of which a marked easterly jet overlies. It was pointed out by Flohn [5] that the disintegration of the jet stream in India is connected with contemporaneous increase of air temperature over the Tibetan Plateau.
In the author's impression, this coincident occurrence of the sudden northward retreat of jet stream and warming over the Tibetan Plateau is probably not fortuitous but indicates a general features. It is easily guessed that in this season the vast and elevated Tibetan Plateau acts as an heat source in the middle troposphere. Staff Members, Academia, Sinica, Peking [14] estimated the mean amount of direct heating (q) from the ground surface of Tibet during summer by considering many effects, such as radiation cooling, condensation heating, and horizontal as well as vertical advection of temperature. Our main concern is to discuss about the problem as to how the initial contour fields (z₀), which is the normal contour height at 300 mb level in May and is presented in Fig. 3, change with time by the effect of (q) just mentioned. For this purpose, we used the vorticity equation (11), where the last term on the right hand side represents the divergence originating from (q). In eq. (11), the term F is used to indicate the sum of several effects associated with the normal fields in May, such as the coupling between the upper and lower layer, the eddy transfer of vorticity, the transformation of horizontal vorticity into vertical vorticity, the divergence originating from the supply of heat in the atmosphere and so on. The value of F can be estimated from eq. (6), where H is the height of mountain. When we put z=z₀ in eq. (11), we get the initial height tendency which is expressed by eq. (12). As stated before, the term on the r.h.s of eq. (12) represents the divergence originating from the direct heating (q) from the ground surface of Tibetan Plateau and is evaluated by making use of eqs. (13) and (14).
After rewriting eq. (11) into a finite difference form, the time integrations of it were performed with the time intervalΔt=1hr. In the three figures of 4, 5, 6 are presented the computed contour patterns for 24hr, 48hr and 72hr, respectively. It appears to clear in Fig. 6 that the jet stream seems to displace to the northern flank of Tibetan Plateau, a pronounced subtropical high centers at the southeastern part of Tibet, and an extended trough stretches along 70°E. These results are in good agreement with findings in the observed patterns during summer, shown in Fig. 8. It may, therefore, be concluded that the direct heating from the ground surface of Tibet plays an important role for causing the sudden northward retreat of subtropical jet stream together with the establishment of subtropical high over Tibet and the formation of new trough near 70°E.

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