WORLD MAPS OF N(z) 



(b) remains higher than average over land 

 areas during their warm seasons due to a steep 

 temperature lapse rate with height. 

 (2) The D 2 scale height, H 2 : 

 shows a minimum in the equatorial region 

 because of the colder temperatures found above 

 the tropical tropopause. 



(3) The wet scale height, H w : 



(a) is larger than average in the general 

 area of the equatorial heat belt during all sea- 

 sons. This indicates a steep temperature gradi- 

 ent with a very small lapse of absolute humidity 

 with height in the turbulently mixed deep layer 

 of warm air. However, in some tropical areas 



2 4 6 8 10 I? M 16 18 ?0 12 24 26 28 30 



FIGURE 1. Three-part exponential fit to mean ti-profile: Koror. 



definite changes may occur in H w because of 

 seasonal shifting of small, but persistent, anti- 

 cyclonic circulations which modify to a consid- 

 erable vertical extent the normal zonal trans- 

 port of water vapor in those latitudes. The 

 seasonal differences of H w in the Coral Sea area 

 seem to confirm the existence of such a cellular 

 structure northeast of Australia [Hutchings, 

 1961]. 



(b) is larger than average over two types 

 of convectively heated continental interiors: 



(1) high-latitude land masses where the 

 sea-level wet term is less than 20 iV-units ; 



(2) temperate desert steppe regions 

 where the sea-level wet term is between 20 and 

 60 TV-units. 



(c) is lower than average in areas where 

 subsidence or tradewind ducting persistently 

 occurs below 3 km. 



(4) The dependence of the dry sea-level 

 values, D , upon temperature (because D = 

 77.6 P/T) is revealed in such features as the 

 332 high in Siberia during February and the 

 260 low in the Sahara Desert during May and 

 August. 



(5) The wet sea-level values, W , are also 



