572 H. MOHN. METEOROLOGY. [norw, POL. EXP. 



From September to March we have maxima of pressure in North America 

 and Siberia, in all months most strongly developed in Asia. The two maxima 

 are connected by a ridge of somewhat lower pressure, forming the wind-divide. 

 This ridge is located between Bering Strait, and the North Pole. It is 

 probable that it migrates from month to month, but the abscence of observa- 

 tions in this region does not, it seems to me, allow any reasonable conclusions 

 to be drawn as to its movements. In April the high pressure in Siberia gives 

 way, and the maximum pressure is located on the American side. This state 

 continues during May, and at the same time the summer minimum in Siberia 

 is steadily increasing in depth. In June we find the highest pressure over 

 arctic North America and at Spitzbergen. In July and August the maximum 

 lies between Greenland and somewhat east of Spitzbergen. 



The Atlantic minimum of pressure extends, from September to April, from 

 Greenland far eastwards into the inner Arctic Ocean. From May to August 

 it is much more feebly developed, and in June it is only found in the western 

 part of South Greenland. 



The contrast between the distribution of pressure in the cold and the 

 warm part of the year is also to be seen in the magnitudes of the pressure- 

 gradients. These are stronger in the winter months, and much more feeble 

 m the summer months. 



The pressure at the North Pole seems to have its maximum, — about 

 764 mm. — in April, and minimum — 759 mm. — from June to September. 

 This gives an annual range of only 5 mm. 



Along the route of the Fram, from the New Siberian Islands to the north 

 of Spitzbergen, the isobars indicate in the winter months south-easterly to 

 easterly, relatively strong, winds on the north side of the Atlantic depres- 

 sion, and in the summer months feeble winds from varying directions. This 

 agrees with our Wind-Tables on pp. 284, 285 and 315. 



For the construction of the Isotherms (PI. XIV — XVI, for the year PI. 

 XX, Sea-Level) I have employed the following publications: 

 1. Klima-Tabeller for Norge. I. Luftens Temperatur. Af H. Mohn. Viden- 

 skabsselskabets Skrifter. I. Matem.-naturv. Klasse. 1895. No. 10. 



