REFRACTIVE INDEX PARAMETERS 



187 



Figure 5.9. Idealized diagram of a fast-moving cold front. 



of figure 4.4 utilize the same data as figure 4.1. The use of A^o produces a 

 simpler map with a smaller range of variation. Additionally, N ^ may 

 easily be estimated from the smooth and slowly varying contours of A^'o 

 providing only that station elevation is known. It was shown in chapter 

 4 that N s may be more accurately estimated from charts of A^o than 

 from charts of N ^ itself by a factor of 4 or 5 to 1 [37]. 



The attempt to find a workable method to compensate for the decrease 

 of A'' with height has brought about the development of various model 

 atmospheres discussed in chapter .3. The paragraphs that follow will 

 outline briefly steps in this development that are relevant to synoptic 

 studies. 



Vertical refractive index cross sections are standard working charts for 

 synoptic studies. Such charts constructed from observed values of N 

 suffer from a serious shortcoming in that the natural decrease of A'' with 

 respect to height effectively masks contrasts between air masses in the 

 lower troposphere. An idealized synoptic example depictmg the con- 

 fluence of contrastmg air masses is presented on figures 5.9 and 5.10. 

 When these idealized systems are analyzed in terms of A'^ as on figures 5.11 

 and 5.12 the most prominent feature is the laminar structure of the A'^ 

 field. 



