6. World Maps of Mean Tropopause Altitudes 



Maps have been prepared of the mean tropo- 

 pause altitudes which were calculated in the 

 course of obtaining the mean iV-profiles for the 

 112 station sample, as discussed previously. The 

 maps, for the 4 "seasonal" months, are shown 

 in appendix D. The zone of maximum tropo- 

 pause altitudes for each month seems to corre- 

 spond quite well with the mean position of the 

 Intertropical Convergence Zone. 



As stated earlier, the criterion for determin- 

 ing the tropopause altitude for each radiosonde 

 ascent was the altitude of the base of the first 

 layer or layers which had a total thickness of 

 at least 2 km and a temperature lapse rate of 

 less than 2°C/km. The mean tropopause alti- 

 tude for each station and for each month was 



determined by a simple average of all of the 

 individual values for the profiles in the sample 

 (usually of 5 years' length). The reliability or 

 consistency of these maps is difficult to assess, 

 since the results of determining tropopause alti- 

 tudes depend to a great extent on the criteria 

 used for selection of the first stratospheric layer. 

 The criterion used here is the one in most com- 

 mon usage [U.S. Weather Bureau, 1964], but 

 other criteria may be applicable where the re- 

 sults are intended for use in specific atmospheric 

 problems. These maps supplement tropopause 

 data presented in other reports and atlases 

 [For example, Willett, 1944 ; U.S. Navy, 1955- 

 59 ; Smith, 1963 ; Smith et al, 1963 ; Kantor and 

 Cole, 1965]. 



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