昭和基地の高層気象と季節循環型の記述

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Seasonal mean values of heights and temperatures at the selected pressure surfaces are computed, using the aerological data obtained during the 4 th (1960) and the 5 th (1961) wintering observations at the Syowa Base, Antarctica. Main characteristics of the seasonal and yearly variations both in the antarctic troposphere and the stratosphere are investigated by means of these limited data. Four vertical time sections (from the surface to 30mb) of Feb. May. Aug. Oct. -Nov., representing each season respectively, are made based on these data, and some notable features of seasonal circulation patterns in 1961 over the Syowa Base are briefly described. In addition, in supplementing this single station data analysis, IAAC's synoptic weather charts in microfilm are used to locate relative pressure systems, and at the same time, for rough estimation of circulation intensity, meridional temperature gradients between the Syowa Base and Marion Island in the middle latitude, together with difference in their annual variations, are utilized. Characteristics of the seasonal circulations in 1961 are summarized as follows : Summer : In the troposphere, weak anticyclonic systems predominate over the east continent and weak circulations of E-ly with slightly N and S components are seen. However, in the location and movement of these systems, W-ly wind circulation is also seen. Cyclonic activities are such that most of lows move on toward the east within the low pressure belt off the base, and, except at the surface, N or NE-ly winds by these systems are very weak in the upper layer, so there was little influence to the air over the base. For the layer from the lower to middle stratosphere, weak W-ly wind generally prevails but variation of the wind direction is also seen upon appearance of anabatic and katabatic fields. In the upper stratosphere, weak E-ly wind with N component can be seen. Autumn : For the layer from the middle troposphere to the lower stratosphere, S or SW-ly strong jets come to be observed due to the sharp southward extension of the middle latitude ridge which brings about a temperature rise in the air over the base. At the same time, in the lower layer near the surface, a shallow cold film of the polar anticyclone is formed and weak surface inversion develops up to about 500 m ; subsequently weak anticyclonic circulation at the surface is maintained. On the other hand, cyclonic activities are intensified from the middle autumn and replacement of the air masses becomes more active. In case a moderate cyclone approaches, a strong NE-ly wind circulation is observed throughout the troposphere. In the upper stratosphere, with advancement of cooling process, a strong W-ly jet predominates following the formation of the polar vortex. Winter : Near the surface, weak SE-ly circulation predominates due to the control of the polar cold anticyclone with moderate surface inversion. In the polar night period, weak circulation of nearly E-ly wind prevails generally for the most part of the troposphere, but even in this period, the base region is attacked by an intensive cyclone of winter. Cyclone activities with strong NE-ly wind are further intensified especially in early and late winter. In some cases this NE-ly wind may persist for several days afterward, with a gradual decrease in its speed only, due to stagnation and filling of the low in the north of the base. There is also found a much more intensified influence of sharp ridge extension southward from the middle latitude anticyclone than autumn, and stronger SW-ly with circulation with a temperature rise is observed. Such an alternative appearance of the NE-ly and SW-ly wind circulation verifies that the antarctic atmosphere is markedly baroclinic in winter time. In the stratosphere, as the polar night cold vortex is in the midst of maximum development, strong W-ly jet more than 100 knots prevails continuously. Spring : Rapid spring-time stratospheric warming which begins with the uppermost layer is found for the period from late October to early November, followed by weakening of the circulation. The NE-ly wind by various-scaled cyclonic turbulence of short period nature is seen in the troposphere. On the other hand, strong SW-ly wind caused by the pressure pattern similar to those in autumn and winter also appears in both the troposphere and the stratosphere. Active replacement of the air masses takes place throughout the whole atmosphere, which is in process of a rapid transition into summer season.
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昭和基地の高層気象と季節循環型の記述

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