Meteorology. — "The Atmospherical Circulation above Australasia 

 according to the Pilotballoon- Observations made at Batavia'' 

 By W. VAN Bemmelen. (Communicated by Dr. J. P. van der Stok). 



(Communicated in the meeting of April 26, 1918.) 



During the years 1909 — '17 numerous determinations of direction 

 and velocity of the wind at different altitudes were made by means 

 of pilotballoon-observations, by the personnel of the Observatory of 

 Batavia; in the beginning with a view to investigating the general 

 system of aircurrents alcove the West of Java, later on aiming at 

 special purposes. Just for this reason the series of observations is in 

 no way homogeneous. Elsewhere 1 will tieat this heterogeneousness 

 in extenso, here however briefly. At present the general results about 

 direction and velocity of the princi()al aircurrents in the different 

 levels will be given. 



In recent years a more or less detailed report on these observa- 

 tions has sometimes been given '); for this occasion the whole material 

 has been subjected to a comprehensive calculation, first the observa- 

 tions have come to an end by lack of balloons, secondly as it was 

 considered advisable not to wait any longer with such a compre- 

 hensive survey. 



A few observations about the endeavours to render the series 

 more homogeneous may lie given here. In the first place for levels 

 under 3 km. observations made between 6 a.m. and 9 a.m. have 

 been taken into account only, in order to limit as much as possible 

 the disturbing influence of land- and sea-breezes, which reach about 

 to the 3 km. level and are weak during those morning hours. 

 Moreover to the results for those lowest levels a special correction 

 derived from the results obtained for the diurnal and semidiurnal 

 variation of the wind has been applied '). 



In the second place of balloon-observations made outside Batavia 



1) Zittingsverslag van 25 Juni 1910. (These Proc Vol. XVllI, p. 149). 



Observatorium, Batavia; Verhandelingen W. 1 



Nature Vol. 87, 1911; Voh 90, 1912; Vol. 91, 1914. 



Luftfahrt und Wissenschaft, Berlin (J. Sticker) Heft 5, 1913. 



Natuurkundig Tijdschrift, Dl. 73, 1913. 

 ») Zittingsverslag van 26 Mei 1917. (These Proc. Vol XX, p. 119). 



