to 26,000 feet the rate of increase, while at first very small, be- 

 comes progressively greater. At 26,000 feet the highest average 

 velocity is reached, 34 m. p. h. The upper limit of the troposphere 

 is also found at about 26,000 feet and is evidently associated with 

 the maximum wind. Average velocities at all elevations are 

 greater in the winter than in the summer, the average difference 

 between the two seasons being 2.5 m. p. h. At 16,000 feet the 

 difference is greatest, 6.3 m. p. h., and at 23,000 feet the difference 

 is least, 1.6 m. p. h. 



SUMMARY OF WINDS 



There are certain factors that should be considered in regard 

 to the evaluation of the wind regime of any region. As is well 

 known, there are shifts in the climatic scheme of the earth. As a 

 rule these shifts are relatively small but in some years they are 

 large and affect the climate of a region materially. These larger 

 climatic shifts may amount to as much as several hundred miles, 

 so that the average seasonal temperature at a given point may 

 equal that usually experienced at a point several hundred miles 

 to the north or south. 



Naturally any climatic shift involves the wind system of a given 

 region. The degree of change in the wind system may be so great 

 that the wind system of one year would differ widely from that 

 of another. Such climatic shifts do occur along the margins of 

 the arctic basin. The desirability of long observational records 

 is thus demonstrated, to give increasing value to a statistical 

 study of climatological data. 



Another factor affecting the representativeness of wind data is 

 the cloudiness factor associated with wind direction. In certain 

 areas of the Arctic, winds from one direction will bring clear 

 skies, and as a consequence winds-aloft data gathered at such 

 times will extend to high altitudes. Winds from other quadrants 

 will bring low cloudiness and observations will be limited. 



Some of the conclusions set forth in this discussion of the arctic 

 wind scheme have been based on records of short duration and 

 weighted in favor of those winds associated with clear skies. 

 These conclusions err in proportion to the unrepresentative char- 

 acter of the data. However, it is believed that the data are such 

 as to justify the statement that the conclusions set forth herein 

 do approximate the actual conditions. 



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