( 



1326 



value is reduced proportionally to the air pressure at 30 km. 

 . 760A , . ,^ 0.11 ^.. 



Notwithstanding the uncertaintj^ attached to this value it is fairly 

 large compared with the amount 0.005 found above for the gradient 

 of the Krakatoa-wind and this makes it probable that the gradient 

 decreases to zero when approaching the equator. 



High Westwinds. Table III shows clearly that the high Westwinds 

 predominate in the southern winter blowing the stronger the larger 

 the northern declination of the sun is. Their average lower limit 

 comes down lowest (16 — 17 km) in June. 



From the separate observations themselves it follows that also at 

 less heights W-winds occasionally were met with; conspicuously 

 more often in March and April than in July— Sept. 



This is in relation with the force of the antitrade, which has a 

 maximum in August and a minimum in April. Therefore it makes 

 the impression that the antitrade squeezes away the W-winds. 



Berson, the discoverer of these winds, observed them in Africa 

 in the months of August and September, but, contrary to Batavia 

 experience, also met with them in lower levels. Now it is remarkable 

 he did not observe at all the predomination of a strong antitrade 

 up to an altitude of ± 16 km. as is the case for Batavia. 



Gold') has drawn the attention to Overbkck's') theory of general 

 circulation in which the western winds of the temperate zones 

 approach the equator in great altitudes. Overbeck did not take into 

 consideration the influence of the oblique position of the earth's 

 axis, but it is evident, that through it W-winds will approach nearer 

 to the equator in the winter-hemisphere. 



Observations at Batavia indeed agree with this, the winds prepon- 

 derating strongly in the southern winter. 



In his theory Overbeck kept separate the currents generated only 

 by the distribution of temperature, from those caused by rotational 

 influence. The latter, however, also depend on the distribution of 

 temperature. Now, it was just for the higher atmospherical layers, 

 that he assumed a wrong distribution; not until many years later 

 was the true one discovered by balloon-soundings. 



Consequently the agreement of Overbeck's theoretical results with 

 the observations cannot be unconditionally accepted as an explanation 

 of the high equatorial Westwinds. 



1) Quarterly Journal 1910. 



2) Sitz. Ber. Preuss. Ak. Berlin. 1888. 



