276 



UPPER AIR OBSERVATIONS. 



6500 

 6000 

 6500 

 5000 



4500 

 4000 



3500 

 3000 



2500 

 2000 

 1500 

 1000 

 500 



-50 



-40 



-30 



-20 



-10 



Fig. 85. Upper air temperatures, summer and winter. 



The numbers given in table 138 have been plotted in figTire 85. 



Summary of winter conditions. 



(a) Durmg cold calm weather in the winter there is a temperature inversion in the 

 lower atmosphere which, however, does not appear to extend much higher than 

 1 or 1| kilometres. 



(h) The mean temperature gradient above the inversion is between 0'40° and 0-50° C. 

 per 100 metres. 



(c) There is generally a discontinuity in the wind direction at the place where the 

 gradient changes sign. 



