316 



REFRACTION AND REFRACTIVE INDEX MODELS 



1,000 

 700 

 500 



N 



ELEVATION = 7m 

 - ^FEBRUARY 



2 4 6 8 10 12 14 



ALTITUDE ABOVE M.S. L. IN km 



Figure 8.4. N distribution for Brownsville, Tex. 



throughout the entire troposphere, with the result that the density scale 

 height is relatively larger than in the case of arctic air. The dry term 

 scale height on figures 8.5 and 8.7 show a distinct tendency to be larger 

 during the warm summer months when the atmosphere is well mixed to 

 great heights. Consequently D decreases slowly with height. 



A slight geographic pattern is observed in the Hd maps: the coastal 

 regions display somewhat higher values than the inland regions. The 

 north-south direction of the isopleths along the west coast on the February 

 Hd map definitely reflects the uniform onshore advection of low-density 

 maritime air. By contrast, the east coast shows an east-west isopleth 

 pattern, the high values in Florida reflecting the well-mixed nature of sub- 

 tropical air, and the lower values in New England inaicating the presence 



