56 



METEOROLOGICAL MEASUREMENTS 



400 



200 



370 380 390 380 390 400 410 

 M 



Figure 9. M curves from the New Guinea area. 



majority of experimental measurements have been 

 made there. Experience indicates that there is not 

 much difference in the types of M curves over land 

 and over sea except that standard propagation con- 

 ditions will in general be much more common over 

 land for reasons that will appear in Chapter 9. In 

 all these graphs the actually measured points are 

 entered so that the reader may gain an idea of the 

 degree of accuracy obtained with this equipment. 



Figure 3 shows a standard curve as measured at 

 the coast of Massachusetts. The linearity of the 

 refractive index in this case is not an accident but 

 is the result of the definite physical condition of 

 thorough turbulent mixing in the lower atmosphere, 

 as will be explained in more detail in Chapter 9. 

 Since this is a fairly frequent condition, standard 

 curves are actually quite common, and in them the 

 measured points cluster well around a straight line 

 as shown in Figure 3. 



Figures 4 and 5 show a set of nonstandard curves 

 selected from a large series of measurements taken 

 on the Massachusetts coast in the summer and fall 

 of 1943. 210 Here the M curves are quite irregular, 

 perhaps more so than is common at other locations. 

 These curves show various types of ducts, some of 

 them rather weak, others with a decrease of M as 

 much as 20 units or even more. 



Figure 6 is a set of M curves that were measured 

 on the east coast of New Zealand, at a point some 

 100 miles south of Cook Strait. 223 These curves 

 provide good examples of the type of M curves that 

 consist of several very nearly linear sections. 



Figure 7 illustrates the typical elevated duct found 

 in the San Diego region. Both below and above the 

 inversion region the M curve is standard. The various 

 curves shown were measured at several distances on 

 a flight from San Diego outward. 



100 



80 



20 



Figure 10. Detailed M curve taken over the ocean near 

 New Guinea. 



The curves of Figure 8 were taken at Taboga 

 Island, some 15 miles south of Balboa, at the eastern 

 entrance to the Panama Canal. They show various 

 familiar types of ducts; two of the curves represent 

 transitional cases where the M curve is steeper than 

 standard but does not bend backward. 



Figure 9 shows two soundings from the tropical 

 Western Pacific. The curve at the left was taken at 

 Biak Island, New Guinea, and is remarkable for the 

 presence of two ducts, a ground-based and an 

 elevated one. The curve at the right was taken 

 at Saipan. 



Figure 10, taken near New Guinea, shows in more 



