METEOROLOGY AND ATMOSPHERIC CHEMISTRY 



79 



ANNUAL 



18 



Lll. 



24 



speed increments are indicated in the figure and are the 

 traditional Beaufort scale values. The data are from U. S. 

 Air Force records, as are the temperature and humidity 

 data above, and were collected at various intervals, hourly 

 over most of the period, with the instrument mounted at a 

 height of 40 feet above sea level. The data are from the 

 years 1945 to 1969 and again correspond in number to 

 14.1 years of continuous hourly observation. Thus the 

 representativeness of these figures is good and falls in the 

 range that one would expect from a sample of 10 to 20 

 years of continuous measurement. We have smoothed the 

 data to report them at eight compass points but were care- 

 ful to use a weighted averaging that preserves the rapid 

 falloff of wind occurrence away from the predominant east 

 and northeast directions. 



This much-noted constancy of the wind is the first 

 aspect of the rose data that we examine. During much of 

 the year, the wind is from the northeast or east 95% or 

 more of the time. From July through October, however, 

 the peak broadens somewhat and moves a bit toward the 

 south so that less than 20% of the winds are out of the 

 northeast. The maximum frequency of winds from the less 

 common directions (southeast around to north) is in 

 August, September, and October, when disturbances are 

 most common and when the equatorial trough is closest on 



12 3 4 5 6 7 8 



1-3 4-7 8-12 13-18 19-24 25-31 32-38 39-46 



1-3 4-6 7-10 11-16 17-21 22-21 28-33 34-40 



03-1.6 2-3 3.6-52 5.7-83 8^-11 11-14 14-17 18-21 



FREQUENCY OF CALMS: PERCENTAGE 

 IS SHOWN IN CENTER OF CIRCLE. 



DIRECTION FREQUENCY; BARS SHOW 

 PERCENTAGE FROM EACH DIRECTION. 

 EACH CIRCLE EQUALS 10%. 

 20% OF ALL WINDS FROM NE. 



SPEED FREQUENCY: FIGURES SHOW 

 PERCENTAGE FROM EACH DIRECTION IN 

 EACH SPEED RANGE. 6% OF WINDS 

 WERE FROM BETWEEN 13 AND 18 mph. 



TABLE: FREQUENCY OF WIND FROM ALL 

 DIRECTIONS FOR EACH SPEED RANGE. 



SPEEDS ARE THE BEAUFORT SCALE: 



MILES / HOUR 

 NAUTICAL MILES / HOUR 

 METERS / SEC 



Fig. 4b 



