Weather Conditions on the Pacific Coast 



The reader can obtain detailed information re- 

 garding the weather in various parts of the State 

 by referring to the bibliography at the end of this 

 paper: For San Francisco (McAdie, 1912), (McAdie, 

 1913); for Berkeley (Reed, 1913); for Lick Ob- 

 servatory (Reed, 1914) ; for San Diego (Carpenter, 

 1913). The following condensed data for San 

 Francisco may prove of interest: 



Pressure. — Mean annual pressure 1017 kilobars 

 (763 mm. or 30.03 in.); highest pressure 1036 kb. 

 (777 mm. or 30.60 in.) ; lowest pressure 985 kb. 

 (739 mm. or 29.10 in.). The absolute range of 

 pressure 51 kilobars, i. e., in equivalent force units, 

 51,000 dynes or 5 per cent of an atmosphere. 



Temperature. — San Francisco has a compara- 

 tively small range of temperature. The annual 

 mean, based upon records covering a period of 

 forty years, 1871 to 1911, and obtained from the 

 mean of the daily maximum and minimum read- 

 ings, is 286** A. (56° F.). A truer value determined 

 from the 24-hourly readings for a period of twenty 

 years, 1891 to 1910, is 285.6" A. (54.6° F.). 



The departures from the mean are comparatively 

 small in all months. The warmest month is Sep- 

 tember, with a mean of 288° A. (59.1° F.), and the 

 coldest month, January, 282.6° A. (49.2° F.). The 

 warmest month has practically the same departure 

 above the mean as the coldest month has below. 

 The annual amplitude is 5.5° A. (9.9° F.). 



The monthly mean temperatures determined 

 from hourly readings are: 



Month j?,y- fXI" Month f»St» ^2"" 



Absolute ^^jj Absolute j^^.^ 



January 283 49 July 289 56 



February 284 51 August 287 57 



March 285 52 September 288 59 



April 285 54 October 288 58 



May 286 '56 November ' 286 55 



June 287 56 December .- 283 50 



The coldest month was January, 1890, when 

 the mean temperature was 281° A. (46° F.), and the 

 warmest month, September, 1889, when the mean 

 was 291° A. (65° F.). 



In an average year there are approximately 

 1311 hours when the temperature is above 289° A. 

 (60° F.) ; 4111 hours when the temperature is above 

 286° A. (55° F.) ; and 7625 hours, or about 87 per 

 cent of the entire year, when the temperature ex- 

 ceeds 283° A. (50° F.). 



Differences between day and night tempera- 

 tures are small. The warmest hour, 2 p.m., has a 



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