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The National Geographic Magazine 



WIND VELOCITIES IN THE ARCTIC OCEAN IN JULY AND AUGUST 



BY TEN-DAY PERIODS, GENERAL MEAN, AND ACTUAL, 



FROM FRAM RECORDS IN GEOGRAPHICAL MILES, 



WITH CURVES SHOWTNG THE MEAN AND MAXIMUM VELOCITIES PER PERIOD 

 FOR ioo HOURS OR 140 HOURS, STARTING FROM CALMS 



As we have already seen, the navigat- 

 ing method adopted and the supply of 

 fuel carried admit of from 100 to 140 

 hours of work by the motors, according 

 to the average horsepower employed. 



It was important to know, as accu- 

 rately as possible, what velocities of wind 

 might be expected in a voyage assumed, 

 in order to have a basis of computation, 

 at 10 days' duration. 



Hence this Synoptic Table was com- 

 piled from thousands of actual observa- 

 tions, showing, first (O) the general mean 

 in July and August, and, second (A, B, C, 

 etc.), the actual winds which prevailed 

 in 14 10-day periods, selected arbitrarily, 

 without reference to whether they would 

 yield favorable or unfavorable results. 



Upon this table are drawn two 

 curves — one of 100 hours of motoring, 

 the other 140 hours of motoring. The 

 motoring, naturally, will be, generally 

 speaking, in calms or the winds of smaller 

 velocity. The table being arranged 

 cumulatively, the. mean and maximum 

 velocity of the wind is shown at a glance 

 for any given number of hours, starting 

 at calms. 



For example, following the 100-hour 

 motor-curve, it is found that in the period 

 of 10 days "O" — general mean — it cuts 

 about halfway between 7 and 8 miles per 

 hour. Hence the maximum wind for this 

 period, with 100 hours of motoring, is 

 7.5 miles per hour, and the mean for the 

 100 hours (falling half way between the 

 total miles per hour for 7 and 8) is taken 

 at 5.6 miles per hour. In period A 

 (actual Fram observations) the 100 



hours of motoring is secured with a 

 maximum wind velocity of a little over 



7 miles per hour and a mean of 5.5. In 

 B period the maximum is 7, the mean 

 6.35, and so on. 



O^the mean of the Fram observations 

 during three Julys and two Augusts, with 

 15 per cent added to allow for greater 

 velocities 100 to 300 feet above the sur- 

 face of the earth. 



A, B, C, etc.=actual winds by 10-day 

 periods, arbitrarily selected, to show how 

 much divergence there is in any given 10- 

 day period from the grand mean compris- 

 ing 155 days. 



For each period the first gives the num- 

 ber of hours of wind at the velocity in 

 miles per hour noted at the top of the 

 table; the second line gives the number 

 of miles of wind movement at that ve- 

 locity; the third, fourth, and fifth lines 

 are cumulative from calms upward. For 

 example, in A, at and including 7 miles 

 per hour, there is a total of 96 hours of 

 wind at that or lesser velocity, with a 

 total wind movement of 520 miles and a 

 mean of 5.41 miles per hour; including 



8 miles per hour, there are 136 hours, a 

 total of 840 miles, and a mean of 6.2 

 miles per hour, etc. 



The totals and means for each period 

 are found in the last column at the right. 

 The mdan of 14 10-day periods is found 

 at the bottom of the table, marked 

 "Totals." The last line of all is the 

 grand mean miles per hour of 155 days 

 for comparison with the mean miles per 

 hour of the 14 10-day periods in the line 

 just above. 



