1916] McEicen: HijdriKjntphic Observations of Scripps Instil ittion 26!) 



Both temperature and salinity observations in San Diego Bay give 

 widely different results, depending upon the state of the tide and the 

 position of the observations ; the values generally increase as the tide 

 falls and as the distance from the entrance increases. For example, 

 at low tide on July 18, 1908. at 8 in the morning, the temperature 

 and salinity near the central part of the bay were 20? 8 C and 34.71Voo 

 respectively ; four hours later, during high tide, at the same place the 

 values were reduced to 18?0 C and 34.04%o respectively. During the 

 same month temperatures as high as 27?07 C and salinities as high as 

 36..50''/„„ were observed in the shallow water off National City, eight 

 miles from the harbor entrance, while at the entrance itself the values 

 were approximately 19?0 C and SS.TS^/oo- 



Our hydrographic observations both in San Diego Bay and in the 

 ocean demonstrate that, while the monthly averages of temperature 

 and salinity at any given position show the same general type of sea- 

 sonal variation, each year is distinct from the others. In fact, averages 

 for each of the several different months have actually differed from 

 those for the same months of other years by amounts comparable with 

 the annual range. Compare especially figure 50 with 51 (pi. 27), 

 figure 62 with 63 (pi. 29), and figure 66 with 68 (pi. 30). 



Again, we have not infrequently found significant differences in 

 temperature and salinity corresponding to different days of the 

 same month at a given position, even ten miles or more from shore. 

 For example, on June 25, 1909, four surface temperatures were ob- 

 served at 32° 52' N and 117° 30' W between 17?6 C and 17?7 C, while 

 three days later, at the same position and time of day, three temper- 

 atures were observed between 19?0 C and 19?2 C. The corresponding 

 salinities were between 33.63Voo and 33.65"/,,,, on the first day, while 

 on the last day they were between 33.68''/„„ and 33.81" \„,. iloreover, 

 large differences may occur at approximately the same time and within 

 a distance of two or three miles of each other, even in regions well 

 removed from land and over deep water. For example, on July 11, 

 1908, midway between San Clemente Island and the Cortes Bank, the 

 surface temperature was 17?2 C and the salinity 33.75''/oo ; twenty 

 minutes later and two miles farther from San Clemente the temper- 

 ature was 15?4 C and the salinity 33.84"/,,,,. 



Nearer shore there are still greater irregularities. For example, 

 on July 25, 1912, about half a mile southeast of South Coronado Island, 

 temperatures simultaneously observed at positions less than sixty feet 

 apart differed by r?5 C: the first was 19?7 C and the second 21?2 C. 



