In order to study the morphology of the subtropical anticyclone, the monthly mean patterns in August were analyzed in the layers from the troposphere up to the lower stratosphere. From the thickness distribution along 30°N at upper isobaric levels, it is seen that in the layers above 500mb level the southern Asia anticyclone shows a higher temperature than in the northwestern Pacific anticyclone. Also it is observed that the anticyclone over the North American Continent shows a lower temperature than the southern Asia anticyclone. The temperature field in the Atlantic anticyclone is not clear. The difference of temperature between the two anticyclones over the Asiatic and North American Continents may be attributable to the different thermal influence of the Himalays and the Rockies, because the temperature distribution may greatly depend on the shape of the large scale mountain. The development (decay) of the northwestern Pacific anticyclone on the 500mb level corresponds to weakening (intensification) of the polar low. However, the strength of the southern Asia anticyclone on the 100mb level is not related to that of either polar low at the same level or the northwestern Pacific anticyclone at lower levels. Therefore we cannot consider that the northwestern Pacific anticyclone at the surface level is linked vertically with the southern Asia anticyclone.* It is speculated that the axis of the northwestern Pacific anticyclone tilts westward with altitude and connects with a separate anticyclone or an anticyclonic cell appearing off the east coast of the Continent of Eurasia. Also the Atlantic anticyclone at the surface level does not connect with the North American anticyclone on the 100mb level. The northwestern Pacific anticyclone and the Atlantic anticyclone predominate in lower layers than in the mid-troposphere, but they are different in intensity. The southern Asia anticyclone becomes stronger than the North American anticyclone in the layers between the 300mb and 100mb levels.
Assuming a steady and horizontal flow and thermal stratification in the Ekman layer, it is investigated how the wind structure in the layer is affected by thermal stratification. For this purpose an extrapolated application of the turbulent transfer relations, which hold in the lowest tens meters, to the entire layer is made. The wind and stress vectors and exchange coefficient are calculated numerically as functions of height, thermal stratification and roughness parameter. It is found that the shape of the Ekman spiral is affected by thermal stratification in such a way that the wind component normal to isobar increases generally with increase of stability. It is also found that the magnitude of the stress decreases with increase of stability, that the wind speed in the lower layer decreases with increase of stability, and that the height of the Ekman layer increases with increase of instability. Comparison of the calculated results with observed data is made on the surface values, indicating fairly good agreement.
In statistics of extremes of a continuous climatic variable, the return period at a geographical point is defined as the mean value of time-intervals between successive two unusual values exceeding a critical amount of the variable. As an extension of this conception we can define the return period on a one-dimensional domain, for instance along a quasi-straight railway line or a highway, as the mean value of time-intervals between two successive unusual values above a certain amount whose return period is T1 years at any point on the domain. The return period on a one-dimensional domain T∞, for instance of heavy rains, is given, under certain reasonable conditions, as follows: T∞=T1/(1+m) Here, m is a constant determined by the nature and the length of the one-dimensional domain and the point return period T1 on the domain, and is given as the sum of probability of simultaneous occurrence of unusual values on adjacent points on the area.
Considering the moist convection from the standpoint of view of scale analysis of disturbance, we obtain the relation of conservation of kinetic and potential energy in a special case of shallow convection. From this energy conservation, the maximum vertical velocity of convective motion is estimated approximately as the function of the parameters such as the ratio of the cloud area to the associated cloudless area and the static stability of the large-scale enviromental atmosphere. In order to examine the qualitative discussion mentioned above, the numerical experiment of thermal convection in a wet air case is performed. The results show a good agreement with those obtained by the qualitative discussion.
On July 9, 1967, severe precipitation took place along the western part of the Japan Islands with the passage of a decaying small scale typhoon. A remarkable disturbance was observed on the thermal structure in the lower troposphere. The amplitude of temperature deviation amounts to more than 2°C, whereas the wave length was as small as 1000km. Another noticeable feature is that the moist adiabatic instability was limited to the lowermost shallow layer over precipitation area and the deep layer above it was unexpectedly stable, suggesting the effect of prevailing convective upward transfer of thermal energy. The large amount of precipitation was supplied by the south-westerly current in a form of moist tongue and by the north-westerly compensating back current as well. The rainfall amount estimated from moisture budget basing on synoptic scale aerological observations was only about 1/3 of the observed rainfall amount, and it is suggested that the effect of mesoscale convergence should be taken into account.
The long term behavior of Kelvin waves is studied, using monthly data on the variance of zonal wind and temperature at Canton Island, for the period September 1954-March 1965. Increased variances are found to accompany the descent of the westerly wind regimes associated with the quasibiennial oscillation. This is indicative of increased Kelvin wave activity within the shear zone which marks the leading edge of the westerlies. There is evidence of a convergence of westerly momentum within the shear zone, which supports the hypothesis that Kelvin waves may play an essential part in the momentum budget of the quasi-biennial oscillation.