If we plot on a geographical map the indices of atmospheric turbulence for the same time in- 

 terval but for different points of the earth's surface, and if we draw the appropriate isolines, we 

 will then obtain the characteristics of individual regions for various months, seasons, and years. 



It is not difficult to see that if we take an individual cyclone, during the time of its passage 

 we will find the greatest atmospheric turbulence along the course of its center. Generalizing 

 further, we may say that the indices of turbulence are greater along cyclone paths than along anti- 

 cyclone paths, since cyclones move faster than anticyclones and the pressure gradients in them are 

 greater. Further, in seasonal pressure regions the turbulence is greater than in permanent re- 

 gions. The latter fact must be particularly emphasized. In stationary cyclones and anticyclones no 

 matter how great the pressure gradients (and consequently the winds), the indices of turbulence are 

 very close to unity, that is, to their least possible value. The index of atmospheric turbulence 

 attains its greatest value at points of intersection of the paths of pressure system centers. 



Thus, while the averaged charts of isobars give a conception of the direction and intensity of 

 air currents, maps of "isoturbulence" of atmosphere which are constructed for the same time in- 

 terval given us give us an idea of the variability of these currents. 



Individual phases of ice behavior depend in the highest degree on the winds. If strong and 

 variable winds of diverse directions prevail in the pre-winter period, we may then expect a strong 

 wind-caused mixing of the upper sea layers in this period, and as a result, a later start of ice 

 formation and massive ice up to the start of melting. If a frequent change of wind velocity and 

 direction takes place in the melting period, we may expect a comparatively early and complete 

 removal of ice from the given sea area. In other words, for navigation in the arctic, most advan- 

 tageous are: least possible turbulence of atmosphere in pre-winter and winter periods and most 

 possible turbulence in pre-navigational period. From this arises the possibility, in my opinion, 

 of using the theory of atmospheric turbulence for long-term ice forecasts. 



The above-described method of computation is extremely cumbersome and can be adopted only 

 in special cases and for special observations. For the answer to practical questions we may assume 

 that the atmospheric turbulence is characterized by the average daily variation in atmospheric pres- 

 sure for the 10-day period, month, season, or year. Since synoptic maps are most completed com- 

 piled in the weather bureau for 7 o'clock in the morning, it is therefore most convenient in practice 

 to consider as the pressure change for the day, the pressure change from 7 o'clock of the preceding 

 day to 7 o'clock of the given day. * 



As an example, table 113 shows the barometric observations of certain polar stations for 1934 

 to 1935 (compiled by the author). 



Examining table 113, we see that the minimum monthly turbulence was observed on 

 Chetyryokhstolboboi Island in June 1936 and was equal to 2.9 mb/day, while the maximum was ob- 

 served in Yogorski Shar Straits in December 1934, and was equal to 2. 9 mb/day, while the maxi- 

 mum was observed in Yogorski Shar Straits in December 1934, and was equal to 9. 2 mb/day It is 

 obvious that the turbulence may be greater in certain few 10 day periods. Thus, in the third 10 day 

 period of December 1934, the turbulence in Tikhaya Bay was up to 12 mb/day, while from 25 to 26 

 October 1934 the pressure at the same station changed quickly by 30 6 mb which was accompanied 

 by a southwest wind of 16 m/second. 



♦Obviously, to obtain such a conventional index of atmospheric turbulence for a longer period 

 (10 days, month, season, year, etc.), we must add the absolute daily pressure changes and then 

 divide the sum obtained by the number of days . 



431 



