SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL, no 



winter months November, December, January, February in the i6 

 years with low sun activity, when r is ^40. The pressure is low with 

 997.7 mb. over Iceland-Jan Mayen, and high over Rumania with 

 1021.7 mb., as well as over Spain with 1019.8 mb. Pressure gra- 

 dients run from SE. and S. to NW. Let us consider now all those 320 



The Average Behaviour of Sea- Level Pressure 

 0$ reloted to all ( 320 ) those Days when the Ionosphere wos 

 particularly Disturbed and to oil (320) those Days when the 

 ^^ ionosphere was particulorly Undisturbed, demonstrated 



,3 p by Meops of Difference- Curves ("Disturbed minus 

 ^Undisturbed" 



Wiqtsrmonths of the 16 Yeors with low 

 Sun- Activity (r^ 40 ) of the Period 

 1906- 1937 



45» - SS'N.L. 

 De Bilt 



5» ll'E.L. 



Karlsruhe 



8° 26' EL 



Potsdam 



I3''4' EL 



Vienna 

 isoaa'E L 



Bresicu 



I7<>5' EL 



Koenigsberg 



20° 30' EL. 



Warsaw 



2l°2' EL 



Lemberg 



24° r EL. 



Kiev 



30- 30' EL 



»5 +7 +9 +11 

 Days After 



Fig. 2. 



days when the ionosphere was particularly disturbed, during the win- 

 ter months, in the years with low sun activity. In figure 5, a synoptical 

 representation is given of the average departures of the sea-level 

 pressure field from the long-period means, i day before these dis- 

 turbed days. There are no considerable sea-level pressure dififerences 

 on this map. The maximum pressure difference within this pressure 

 field amounts only to 1.2 mb. Figure 6 shows the same conditions 



