thus much weaker than that of the more extended land masses of the 

 Northern Hemisphere, where, for instance, the temperatures over the 

 Sahara are higher and their difference against those of the Atlantic 

 Ocean is larger than in Australia. 



The coolness of the southern summer in higher latitudes is the most 

 marked difference between the surface temperatures in the Northern 

 and Southern Hemisphere. Beyond 40° of latitude the southern atmo- 

 sphere is now found ta be not only near the ground, but to a height of 

 8 km. 8-10° c. colder than the same latitudes in the Northern Hemisphere. 

 This difference indicates the influence of the different distribution of 

 land and sea upon the heat content of the bulk of the troposphere, 

 but is probably mainly caused by the higher cloudiness and albedo of 

 the Southern Hemisphere. 



In winter (Fig. 1) the coldness of the antarctic stratosphere and the 

 gradual obliteration of the tropopause towards the end of winter are 

 the most marked features of the temperature distribution. At a 

 level of 16 km. the average winter temperature in 78° S. is likely to 

 fall to —80° c. A strong fall of temperature in the stratosphere in 

 winter is found in the North Polar regions, too ; but the average tempera- 

 ture remains still about 10° higher than above the Antarctic. Another 

 interesting fact revealed by the temperature cross-section for the winter 

 is the strong decrease of temperature in the troposphere between 20° 

 and 40° S. A similar large temperature gradient is found in the Northern 

 Hemisphere in slightly higher latitudes on the eastern sides of the North 

 American and Eurasian Continents. This makes it somewhat doubtful 

 whether this temperature gradient is in the south a feature that is 

 characteristic of the whole hemisphere or whether is applies only to the 

 longitude of the cross-section. 



The stratosphere has in winter the highest . average temperature in 

 40-50° S., whilst the temperature is lower towards the Pole as well as 

 towards the Equator. Such a temperature maximum appears in the 

 north, too, but it is more marked in the Southern Hemisphere. 



With regard to the tropopause, Fig. 3 shows its average height in 

 the southern cross-section and the average for the Northern Hemisphere. 

 The observations suggest a discontinuity in the tropopause around 35° 

 latitude which corresponds to one recently established in the Northern 

 Hemisphere. A study of the frequency distribution of tropopause 

 heights confirms the reality of this break. In summer the height of the 

 southern tropopause beyond 40° S, is very similar to that of the northern 

 tropopause in winter. Neither our cross-section nor the- formerly 

 mentioned data from the South Atlantic Ocean corroborate the claim 

 for an extremely low position of the tropopause in the region of Kerguelen 

 Island (lat. 50° S.). 



In imnter the height of the tropopause south of 30° S. is somewhat 

 lower than in the Northern Hemisphere. The almost identical height 

 at Melbourne (38° S.) and Macquarie Island (54° S.) appears well sub- 

 stantiated. Data from Little America give in winter a height of the 

 tropopause of between 8 and 8i km., almost the same as in summer ; 

 this small difference between summer and winter appears at some places 

 in high northern latitudes, too. The heights of the principal isobaric 

 surfaces show; above 3 km. the disappearance of the subtropical high- 

 pressure belt. , In Summer (Fig. 5) the slope of the isobars is steepest near 

 the 300 mb. level. The inclination of the isobars is greater than in the 

 Northern Hemisphere. 



58 



