SAUR: SEA LEVEL DIFFERENCES 



158° 



154° 



I I I 



,- ^Atwzo «z 



Honolulu ^3^ 05 I 04 A-^ 



Twzo 1 LfS^,! [ 



Hilo 



J L 



1 r 



38°|- CCOFI MSB -|38° 



6O6OA "ASon Froncisco 



126° 124° 122° 120' 



Figure 3. — Locations of hydrographic station data used 

 to determine long-term differences in sea level as re- 

 ferred to in text and in Table 2. CCOFI = California 

 Cooperative Oceanic Fisheries Investigations. TWZO 

 = Trade Wind Zone Oceanography program. Two-digit 

 numbers are 1-degree square (dashed lines) identification 

 used in National Oceanographic Data Center listings of 

 hydrographic station data. 



I I I I I I I I 



HONOLULU-MINUS-SAN FRANCISCO 

 I I I I I 



JFMAMJJASONOJF 



Figure 4. — Seasonal deviations of 65-year normal (1905- 

 69) monthly sea levels (trend removed and adjusted to 

 normal pressure) from long-term mean, Honolulu and 

 San Francisco (below) . Seasonal cycle of normal month- 

 ly sea level difference (above). Difference of long-term 

 mean sea level of 58 cm was determined from hydro- 

 graphic station data (see text). 



probably due to heating, giving v^^ay to a more 

 gradual rise into autumn, results in a slight dip 

 during July in the plateau of the difference. The 

 sea level at Honolulu drops rapidly from October 

 to January. At San Francisco, however, the sea 

 level continues to rise from November to its 

 highest value in January. Some of this rise is 

 undoubtedly the result of the frequent occur- 

 rence of the north-flowing coastal countercurrent 



in these months (Reid, Roden, and WylHe, 1958) , 

 while some may be due to decrease in the speed 

 of the south-flowing current offshore. The pro- 

 portions cannot be determined from the sea level 

 data. The combined changes at Honolulu and at 

 San Francisco result in a sharp winter min- 

 imum in the normal cycle of sea level diflference. 



HILO-MINUS-AVILA 



The seasonal variation of the normal monthly 

 sea level difference for Hilo-minus-Avila (Fig- 

 ure 5) is similar to that for Honolulu-San Fran- 

 cisco. A winter minimum occurs in December- 

 February, and the maximum occurs in the 

 spring. However, after a decrease of a few 

 centimeters to July the normal difference re- 

 mains at a nearly constant level through Oc- 

 tober rather than rising again as it did for Hono- 

 lulu-San Francisco. March and November are 

 transitional months except that March has a 

 normal difference as high as those for late sum- 

 mer. The range of the normal seasonal cycle 



JFMAMJ JASOND 



Figure 5. — Seasonal deviations of 20-year normal (1947- 

 59, 1961-67) monthly sea level (trend removed and ad- 

 justed to normal pressure) from long-term mean, Hilo 

 and Avila (below). Seasonal cycle of normal monthly 

 sea level difference (above). Difference between long- 

 term mean sea level of 52 cm was determined from hy- 

 drographic station data (see text). 



625 



