582 



H. MOHN. METEOROLOGY. 



[nORW. POL. EXP. 



The winter shows a little higher average than the other seasons. This 

 is caused by the relatively large proportion of comparatively high minima of 

 pressure observed in the depressions of the winter months. 



As the lowest observed pressures in most cases are higher than the 

 pressure at the centre of a passing depression, the figures in the Table are in- 

 capable of showing even an approximate value for the mean or absolute pressure 

 of air in the centres of depression. We can only say that it must be below 

 747 mm. 



The next Table contains 10 cases in which the centre of a depression 

 has passed the Fram. In these cases the lowest pressure has been 



The mean of these pressures is 74-2"3 mm., and we may take 740 mm. 

 as an approximate value of the mean minimum pressure in a cyclonic centre. 

 The lowest pressure observed on board the Fram is 724'1 mm., on the '^'2P-^ 

 February, 1896. The absolute minimum in the Arctic Ocean is of course 

 lower. 



A list of the observed minima of pressure will be found on p. 396. 



