NO. 8 



BAROMETRIC PRESSURE — DUELL AND DUELL 



23 



measure, is repeated only 7 days after the invasion. The ampHtude 

 of tlie sea-level pressure reaction is also here greater in winter 

 (5.3 ml).) than in summer (2.8 mb.). 



With the aid of the data of the absolute topography of the 500-mb. 

 surface, which are likewise published in the Taeglicher Wetterbcricht 

 of the Deutsche Seewarte for an area between 45° and 60° N. lat- 

 itude and 5° W. longitude and 25° E. longitude, an attempt has 

 been made to answer the question, "Docs the pressure at a height 

 of approximately 5,000 m. react to strong ultraviolet invasions, and 



The Average Behaviour of Moximum Interdiurnol Increases in Sea- Level 



Pressure over me Areo 45''Nl.fo 60»NL end IG'WLto 20*Ei, os reloted to oil 



(51) very Intense Ultraviolet Radiation - Invasions (between 0900 and isoo «mt > 



which were not preceded on the previous 5 Ooys by equally strong Invasions. 



fflb 



Summer ^^ 



mb t«'">L TO tlPTIMIC*! 



10 1936 - 1941 9 



All Seosont 



8 1936 - 1941 



Winter e 



CTotia TO ■••ca I 

 1936- 1941 7 



UJ_ J_l_l_l_l_i_l 



-I ^A ^ *S *7 .9 

 B*tor« Dor* *'*•' 



1936-1938 



1936-1941 



1939-1941 



J '■■'■■''' 



-I *l *S *B *T ** 



Btfor* Oo|r> A()*r 



Fk;. 18. 



if so, how?" This special investigation has been made by the same 

 method and with the same key days of the years 1936 to 1941 as the 

 other statistics, demonstrated in the figures 17 and 18. In figure 19 

 some of the results of this investigation are shown. The three maps 

 on the left-hand side of the figure represent the average change 

 of the absolute topography of the 500-mb. surface in dkm. which 

 has taken place on all the days with very intense ultraviolet invasions 

 since the immediately preceding day, above for the summer months 

 April to September, in the middle for all seasons, and below for the 

 winter months October to March. The distribution of the isallohypses, 

 or lines of equal change of height, on these maps is rather irregular ; 



