NO. 17.] BAROMETRICAL DEPRESSIONS AND THEIR MOTION. 577 



BAROMETRICAL DEPRESSIONS AND THEIR MOTION. 



The observations of the pressure of air, contained in pp. 26 to 248 

 of the journal, and still more clearly the barograph papers, show by the fall 

 and rise that cyclonic weather-systems, barometrical depressions, or "Lows", 

 were passing through the regions of the Arctic Ocean visited by the Fram. 



The great distance between the Fram and any permanent or temporary 

 meteorological station, makes it quite impossible to construct synoptic weather- 

 charts by means of which we could find the position of cyclonic and anti- 

 cyclonic systems, and study their depths or heights, their gradients, and their 

 motions. What the observations show, for this purpose, is only the variation 

 of the barometer and the change of the direction of the wind. These observa- 

 tions I have used in the following manner, in order to find out something more 

 about the motions of barometric depressions, than the above-mentioned 

 results from the general change of the direction of the wind (p. 287) and 

 from the baric wind-roses (p. 399) and the wind-roses for the change of pressure 

 (p. 400) have been able to do. 



For the latitude, (p = 82°, and the friction coefficient, k = 0'00007, we 

 have the normal angle of deflection^ of the wind's direction from the direc- 

 tion of the gradient, a equal to 64°. A line drawn to the left of the wind's 

 direction (the back to the wind) forming an angle of 64° with that direction 

 will approximately show the direction of the gradient and the bearing of the 

 centre of the depression. For each passing depression, such lines, drawn from 

 the ship's position, will spread out so as to cover a sector, and their mean 



2 ca sin y 

 » tan a = ^ 



73 



