[stupart] PRESIDENTIAL ADDRESS 5 



We have then a general knowledge of some of the phenomena 

 of atmospheric circulation which lead to normal pressure distribu- 

 tion over the Globe, but we are as yet almost wholly ignorant of many 

 of the factors which lead to disturbances which occur as cyclone and 

 anti-cyclones in the higher latitudes. We do know, however, some- 

 thing of the conditions which are very obviously connected with the 

 development of cyclones — perhaps indeed we have more certain know- 

 ledge regarding this than of any other meteorological activity, e.g., 

 in the colder seasons when cold continental winds in the rear of a shal- 

 low trough of low pressure reach the coast line of the Gulf of Mexico 

 or the Middle Atlantic, there is almost certain to be a marked storm 

 development with heavy precipitation. Moist warm air of the Gulf 

 Stream on one side and cold dry continental air on the other lead to 

 a rapid cyclonic development and the greater the contrast in tempera- 

 ture, the more pronounced will be the storm. The conditions leading 

 to anticyclonic development are not so clearly defined and observa- 

 tion of weather maps does not shew with any degree of conclusive- 

 ness what particular conditions lead to the formation of the travelling 

 anticyclones which move southeastward across the Canadian Dominion. 



There is, however, reasonable ground for belief that the North 

 American anticyclone, at least in its initial stages, like that of Asia, 

 is largely the outcome of the cold of radiation which in the absence 

 of marked cyclonic conditions impinging on the Pacific coast, pro- 

 duces low temperature and increasing pressure in the higher latitudes. 



The daily reports now received from Great Britain, North Europe 

 and Iceland, in one hemisphere, and those from Canada' and Alaska 

 in the other hemisphere, render it possible to draw the isobars with a 

 fair degree of accuracy about the two great centres of cyclonic action 

 in Atlantic and Pacific and by interpolation it is possible to deduce 

 with but a small' margin of doubt the run of the isobars over the polar 

 sea. 



The charts prepared with this data show pretty conclusively that 

 some of the anticyclones which move over North America are of 

 Asiatic origin. There are others, however, which very obviously 

 develop as they move southward from the Mackenzie river territory, 

 and others again which come in from the Pacific in middle latitudes. 

 These several movements are each characteristic of different types 

 of seasons and could we solve the problem of the construction of these 

 anticyclones a long step in advance would be made towards fore- 

 casting seasons. 



But there are some glimpses of light on the subject and no better 

 examples of the conditions which lead to a complete cutting off of 

 Siberian highs and the lack of highs in the far N of Canada — can be 



