METEOROLOGY OF TRANSMISSION EXPERIMENTS 



71 



sideiiee. Consetiuently the depth of this maniie struc- 

 ture is diminished by the lowering of the base of the 

 inversion. 



Figure 5 shows the typical structure of a moderately 

 high inversion. Usually the lapse rate of temperature 

 below the base approaches, and in some cases exceeds, 

 the dry adiabatic condition. This vertical mixing in- 

 sures a homogeneous air mass characterized by the 

 constant vapor pressure in the marine stratum. 



Figure 6 shows the typical elevated S type M curve 

 for this condition. 



340 



360 



380 400 

 M 



420 



440 



Figure 6. M curve corresponding to the inversion shown 

 in Figure 5. 



The discontinuity surface between the two distinct 

 air masses exists over a large area. Soundings have 

 been confined within a 130-mile radius of the labora- 

 tory, but observations on an FC radar indicate trap- 

 ping conditions existing between San Diego and Guad- 

 alupe Island 225 miles to the southwest. 



*•*■* Shape of the Inversion Surface 



Emphasis must be placed on the fact that the dis- 

 continuity surface is not horizontal over the area but 

 is at any time a warped surface. Figure 7 shows a 

 series of M curves taken by airplane to the seaward 

 of the laboratory. Both the height of the inversion 

 and gradients in the transitional layer vary greatly 



6000 



4000 



jooo 



2000 



1000 



340 360 360 400 420 440 460 460 490 



M 



Figure 7. M curves at different distances and times. 



with distance. Eepeated soundings indicate that the 

 apparent slope is not due to large scale lowering dur- 

 ing the time interval between observations. The cluster 

 of IL values along the mean lapse rate of il/ in the 

 upper and lower strata indicates the homogeneity of 

 the two air masses along the vector. The possibility 

 of the coexistence of elevated and surface gradients 

 has been considered. No significant surface discon- 

 tinuities have been detected. 



There is a general tendency for the base of the in- 

 \er.sion along tlie shore to liave a maximum height at 

 0800 and a minimum at KiOO. Througli the exchange 

 of meteorological data between the University of Cali- 

 fornia at Los Angeles and the laboratory this fact is 

 now fairly well established. 



Figure 8 is a plot of refractive index from a series 

 of plane soundings. The diagonal lines show the 

 height and distance from the base at which measure- 

 ments were made. Each line is marked with the time 

 of beginning and ending the flight. The numbers at 

 the ends of the curves are the refractive index (n — 1) 

 multiplied by lO''. The indices are independent of fre- 

 quency for this range. Again it is noted that conditions 

 vary along the vector. 



Figure 9 is a plot of refractive index taken by air- 

 plane along the San Diego-San Pedro path, indicat- 



