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THE LATITUDE SHIFT OF THE STORM TRACK IN THE 

 11-YEAR SOLAR PERIOD 



Storm Frequency Maps of the United States, 1883-1930 



By C. J. KULLMER 



Syracuse University 



The United States is unique among nations in possessing a splendid 

 series of maps of tracks of barometric depressions. These have been 

 pubHshed each month from 1874 to the present in the Monthly Weather 

 Review. Nothing similar is available for any other part of the world. 



For the lo-year international period from 1878-87 H. H, Dun- 

 woody published in 1893 storm frequency maps for the whole of the 

 Northern Hemisphere. Dunwoody divided the map of the Northern 

 Hemisphere into squares measuring 5° on a side and recorded the 

 number of centers of barometric depressions that crossed each square. 

 In order to determine whether a general shift of the storm track had 

 taken place in an interval of 21 years, I remade the maps of storm 

 frequency in the United States for 1899-1908 according to Dun- 

 woody's plan of 5° squares.^ A comparison of the two periods showed 

 a slight but definite southerly and westerly shift. 



Considering the numerous observed correlations between sun spots 

 and meteorological elements, it seemed worth while to ascertain whether 

 or not Spoerer's latitude shift of sun spots is accompanied by a cor- 

 responding latitude shift of the vortexes in the earth's atmosphere. 

 This latitude shift is one of the most striking features of the sun-spot 

 cycle; each new cycle begins at about 25° solar latitude and ends at 

 10°, with maximum positions of about 30° and 5°. 



For such a study it is evident that 5° of latitude, approximately 

 345 miles, is too large a unit. I have, therefore, chosen a unit area half 

 the size of Dunwoody 's, namely 5° in longitude and 2V in latitude. 

 The series of year maps from 1874- 191 2 were made in 191 3, furnish- 

 ing comparison material for three solar periods ; since then two more 



"■ The shift of the storm track. Chap. 16 in Huntington, The climatic factor, 

 Carnegie Inst. Publ. 192, 1914. 



Smithsonian Miscellaneous Collections, Vol. 89, No. 2 



