the east and west partly cancel each other. These restrictions are, 

 however, probably less important in the Southern Hemisphere, where 

 in the higher latitudes the actual flow is likely to be more purely from 

 west to east than in the Northern Hemisphere. Figures 6 and 7 give 

 the average zonal motion of the atmosphere as computed from the 

 slope of the isobaric surfaces. 



In summer (Fig. 7), in accordance with the stronger inclination of 

 the isobaric surfaces, the zonal wind component is generally stronger 

 in the Southern than in the Northern Hemisphere. At the 5 km. level, 

 for instance, in temperate latitudes between 35 and 65° the zonal 

 component in the south is nearly twice that of the north. 



Just below the tropopause a maximum of the zonal wind component 

 exists as in the Northern Hemisphere. 



In winter (Fig. 6) the zonal wind velocities, of the Southern Hemis- 

 phere are only slightly bigger than in summer. The small seasonal 

 difference in the intensity of the circulation which characterises the 

 surface layers in the higher latitudes of the Southern . Hemisphere is 

 found to extend through the whole troposphere. A remarkable feature 

 of the southern pross-section is a minimum of the zonal wind component 

 near 50° S. at the levels above 3 km. As a whole the intensity of the 

 zonal circulation in our section through the Southern Hemisphere does 

 not differ much from the average conditions in the Northern Hemisphere. 

 Here again the more fundamental difference between the Northern and 

 the Southern Hemisphere exists in summer rather than in winter. 



A MERIDIONAL -ATMOSPHERIC CROSS-SECTION FOR AN 

 OCEANIC REGION 

 By J. W. HuTCHiNGS, New Zealand Meteorological Service 

 1. Introduction 

 At the present time meteorology does not have a generally accepted 

 and adequate theory of the general circulation of the atmosphere. To 

 some extent this is due to the lack of suitable theoretical tools, but 

 it is at least as much due to the paucity of observational data over 

 large areas of the globe. • The lack of observational material is especially 

 striking" in the Southern Hemisphere^ — pai"ticularly in the oceanic 

 portions — from which, until very recently, ahnost no free air observa- 

 tions were available. The aim of this preliminary paper is to bring 

 forward some of the upper air observations that were made in the Pacific 

 region during World War II, and to set them in relation to the upper 

 air data available from stations in New Zealand. In order to present a 

 more complete picture of the southern circnlation some rather scanty 

 Antarctic data are also included. 



2. Observational Material 

 The following is a brief description of the observational material used 

 in this study. All the temperature data used were obtained by standard 

 Frieze radio-sonde equipment and were evaluated in the standard manner 

 as prescribed in U.S.W.B. Circular P. While working with the records 

 it was noticed that daylight flights almost invariably yielded higher 

 temperatures than flights made in darkness, the dift'erence being of the 

 order of 3° c. It would seem that the greater part of this difference 

 is due to insolational heating of the instrument and that records from 

 daylight flights are consequently unreliable. In this study only night- 

 time flights have been considered except for the inclusion of a few 



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