Chapter 5. Synoptic Radio Meteorology 



5.1. Introduction 



This chapter treats the variation of refractive index structure in the 

 troposphere with synoptic tropospheric disturbances. Within the scope 

 of the synoptic field are timewise and spacewise variations in the atmos- 

 phere from microscale fluctuations to broad-scale systems of weather map 

 dimensions. 



The microscale fluctuations of the refractive index are those that one 

 would expect to observe at a particular point along a radio path that 

 reflect detailed terrain and weather conditions in the immediate vicinity 

 of, say, the transmitter or receiver site. 



Mesoscale variations, by way of contrast, are those which cover tens 

 of kilometers and thus encompass a substantial portion of a radio path. 

 Examples of this type of variation are land-sea breeze effects and con- 

 vection cells of thunderstorm activity. 



Large-scale weather systems, affecting vast areas, perhaps even on a 

 continental scale, fall under the classification of macroscale variation. 

 Examples of this type of activity in the atmosphere are sweeping air mass 

 changes and frontal systems traversing thousands of kilometers on the 

 earth's surface. A detailed analysis of such a system is given as an illus- 

 tration later in this chapter. 



5.2. Background 



The problem of determining the vertical and horizontal distribution of 

 the radio refractive index has engaged the attention of radio meteorologists 

 on an international scale for the better part of two decades [1, 2, 3, 4, 5, 



By analysis of current synoptic conditions from standard weather 

 charts, one may ascertain the air mass type appearing over a given region 

 and, likewise, may predict with reasonable accuracy the air mass type 

 expected over a particular locale in, say, 24 hours. Then, from the air 

 mass profile characteristics table of section 4.4, one is able to estimate 

 what the departures of refractive index (and radio ray bending) from 

 normal will be over a certain region. The bending predictions permit an 



Figures in brackets indicate the literature references on p. 224. 



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