INTERACTION BETWEEN THE ATMOSPHERE AND THE OCEANS 225 



took place but if horizontal ocean currents were lacking, there would still 

 be a marked difference between the climate of the land and that of the 

 oceans, and a difTerence between the climate of the coast and that of the 

 inland areas. The climate over the oceans would be much more uniform 

 than that over the continents, and the climate of the coasts would be 

 milder than that over the inland. When dealing with actual conditions 

 it must be taken into account that ocean currents exist that also tend to 

 modify the distribution of temperature of the surface waters and to bring 

 into one area waters that are abnormally warm and into another area 



Fig. 63. Annual variation of air- and sea-surface temperatures at 

 Yokohama and San Francisco. 



waters that are abnormally cold. Thus the circulation of the ocean will 

 alter the climate over the sea itself and will modify the climate of the 

 coasts, because the current flowing along one coast may be abnormally 

 warm and the current flowing along another coast may be abnormally 

 cold. The influence will evidently depend upon the character of the 

 currents, which, again, is controlled by the prevailing winds and the 

 processes of heating and cooling to which the waters of these currents have 

 been subjected in course of time. 



The difference in climate between the east coasts and the west coasts 

 in middle latitudes can be brought out by considering specific examples of 

 difference in the annual march of temperature on both sides of the Pacific 

 Ocean. Yokohama and San Francisco are nearly in the same latitude, 

 but the annual march of temperature in these localities is widely different, 

 as is evident from fig. 63, in which the mean monthly temperatures are 

 shown. At Yokohama the average temperature of the coldest month is as 

 low as 3.0°, but the warmest month has an average temperature of 25.4°. 



