22 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. II O 



The great similarity between the summer curves and the winter 

 curves represents a criterion of reality which should not be under- 

 estimated, because the summer and winter months are completely 

 independent of each other in these statistics where only daily values 

 were used to investigate short-term impulselike solar influences. Fig- 

 ure 1 8 shows the average behavior of the maximum, interdiurnal in- 

 creases in sea-level pressure, occurring within the preceding 24 hours 

 over the area 45° to 60° N. latitude and 10° W. longitude to 20° 

 E. longitude on all days with very intense ultraviolet invasions, and 

 moreover on i preceding and 8 following days. The respective mete- 



The Average Behaviour of Seo-Level Pressure (uoo gmt ) 

 OS reioted to oil (51) very Intense Ultraviolet Radiation - Invasions (between 

 0900 AND isoo GMT ) which were not preceded on the previous 5 Days by equally 

 strong Invasions. ^^^^ _ ^^^^ 



Hambur 



Frankfurt a.M. 



Vienna 



Summer 



' SCPTCMaCII \ 



1016 



xAII Seasons 



llOIS 



I .^3 

 Before Days 



Fig. 17. 



orological data were taken out of the daily isallobaric maps, published 

 in the Taeglicher Wetterbericht by the Deutsche Seewarte in Ham- 

 burg. For this representation a subdivision was undertaken, not only 

 in summer and winter, but also in years with increasing sun activity 

 (1936-1938), and in years with decreasing sun activity (1939-1941). 

 Even here the great similarity of the curves with each other is strik- 

 ing, and the more important because the groups of years and seasons 

 are again completely independent of each other. The maximum inter- 

 diurnal increase in sea-level pressure over the middle and western 

 part of Europe takes place, on the average, 2 to 4 days after very 

 intense ultraviolet invasions. One day after the invasion the maxi- 

 mum pressure rise has a particularly low value; this, in similar 



