CLIMATIC CLASSIFICATION BY No 



103 



in table 4.3, are intended to give a general idea of the geographic and 

 climatic character of the majority of the stations found within given 

 values of range and yearly mean of N s. 



Table 4.3. Characteristics of climatic types 



For a given classification of refractive-index climate, diverse meteor- 

 ological climates and geographical regions may be represented. Note, 

 for example, that type V of table 4.3 includes stations from Mediterranean 

 and marine as well as polar climates. Mediterranean stations in this 

 category fail to attain a high range because of the characteristic dryness 

 of the subtropical high-pressure pattern that is generally found in this 

 area during the summer months. Polar and marine climates in this 

 group maintain a low range due to suppressed humidity effects as a result 

 of low to moderate year-around average temperatures. 



Annual trends of N s for stations typical of each climatic division are 

 shown by figure 4.14. 



Yet another facet of the climate is the year-to-year variation of the 

 monthly mean value of N s. Five consecutive years of monthly means 

 were prepared for each of the six typical stations whose annual cycles are 

 shown in figure 4.14. Then, for each month, the absolute value of the 

 difference between consecutive years was obtained. These values were 

 then averaged for all months and are listed in the second column of table 

 4.4. 



