KUI'KUSUNTATIVK OHSKKVED M CUttVliS 



55 



200 



ioo 



360 365 370 375 380 360 365 370 375 380 



u. 600 



300 



1900 



MARCH 9,1944 



350 355 360 365 



2100 



MARCH 9,1944 



355 360 365 370 375 375 380 385 390 395 375 380 385 390 395 



M 



Figure 8. M curves from Taboga Island near Balboa, Canal Zone. 



commonly use multi junction dry and wet thermo- 

 piles which have the advantage of not requiring 

 elaborate calibration. In connection with captive 

 balloons this type of equipment is somewhat clumsy 

 in that the cold junctions have to be carried aloft 

 in a Dewar flask. 



It should be noted here that the ordinary 

 noncaptive radiosonde as used in the routine meteoro- 

 logical observations of the U. S. Weather Bureau and 

 of the Armed Services is not suitable for radio- 

 meteorological purposes. The reason is that these 

 sondes are designed to give representative data only 

 at definite and fairly large vertical intervals, 100 ft 

 or more. These are too widely spaced to yield a 

 representative M curve, as the characteristic features 

 of the latter are usually concentrated in the lowest 

 strata of the atmosphere. 



Wind measurements are of importance in connec- 

 tion with propagation problems, for reasons which 

 will be given in detail in the chapter on weather 



forecasting. They are particularly significant at 

 coasts when off-shore winds or land and sea breezes 

 are present. Sensitive and carefully calibrated 

 anemometers with ordinary wind vanes prove 

 adequate for measurements of this type. Special 

 equipment such as supersensitive anemometers, 

 developed for particular purposes such as chemical 

 warfare problems, are not usually needed because 

 the large area covered by radio transmission paths 

 or radars renders too detailed measurements useless. 



76 REPRESENTATIVE OBSERVED 



M CURVES 



A small catalogue of M curves that have been 

 actually measured in various parts of the world by 

 means of the equipment described previously con- 

 cludes this chapter. Most of the curves presented 

 were taken over the ocean merely because the 



