Oceanic Circulation and Temperature 

 low temperature of which appears to result from 

 a cooling of that part of the Japan Stream border- 

 ing the coast, has long been admitted, attempts to 

 account for the reduction in temperature have given 

 rise to many different hypotheses. 



This cold coastal water is of interest from a 

 meteorological point of view, since there are good 

 reasons for believing it to be the cause of the 

 relatively cool summers of the California coast. 



Average Temperatures of the Pacific. — Except 

 for the comparatively narrow margins bordering 

 the continents and islands, where the depth is less 

 than a thousand fathoms, the bottom water is char- 

 acterized by a remarkably uniform temperature, 

 varying from 34° to 36° Fahrenheit. From latitude 

 40°, near Cape Mendocino, to latitude 30°, 150 miles 

 south of San Diego, the water below a depth of 

 500 fathoms rarely exceeds 39°; and at a depth of 

 200 fathoms, the average temperature of the eastern 

 half of the Pacific is 46°, while that of the western 

 half, though higher, rarely exceeds 50°. The annual 

 variation of temperature is scarcely perceptible 

 below 150 fathoms, while the surface temperature 

 of most of the Pacific has an annual range varying 

 from a minimum of 4° at the equator, to a maximum 

 of 18° at latitude 40°. 



A Comparison of In-shore and Off-shore Tem- 

 peratures. — Between latitudes 45° at Puget Sound 

 and 25° at the southernmost point of Lower Cali- 

 fornia the mean annual surface temperature is pro- 

 gressively lower as the coast is approached. This 

 fall in the mean annual temperature is clearly in- 

 dicated at every depth from 250 fathoms up to the 

 surface, where there is an in-shore temperature 

 averaging 5° less than that found 1000 miles off- 

 shore. Also, in general, the western shores of the 

 islands off southern California are bordered by 

 colder water than their eastern shores. 



Some of the most interesting facts relative to 

 the average monthly surface temperatures in-shore 

 as compared with those off-shore are shown in the 

 tables on the following page. 



The tables show that the off-shore surface tem- 

 peratures at latitude 30° are much below the normal 

 (the temperatures given in the first column), while 

 those at latitude 40° are somewhat greater, at least 

 in winter. Also it appears that the annual range 

 of the off-shore temperatures agrees with the normal 

 range for the same latitude. But the in-shore tem- 

 peratures are notably less than the others for the 

 same latitude, especially during the warmest part 

 of the year, and consequently have less than the 



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