80 



DISTRIBUTION OF SALINITY, TEMPERATURE, DENSITY 



that any temperature value above or below that determined by the tem- 

 perature-salinity relation could be considered as resulting from heating or 

 cooling of the water, and used the method within three areas in the eastern 

 North Atlantic. Fig. 18 shows the curves that he determined for an area 

 off the Bay of Biscay with its center in approximately 47°N and 12°W. 

 The character of the curves, the reduction of the range, and the displace- 

 ment of the times at which maxima occurred clearly show that one has to 

 deal with heat conduction. In this case the variation in the heat content 

 corresponds nearly to the variation in net radiation, whereas in the 

 Kuroshio the additional effect of excessive cooling in winter by winds 

 from the continent leads to much greater variations in temperature and 

 heat content. 



M J J A 



MONTH 



Fig, 18. Annual variation of temperature at different 

 - depths off the Bay of Biscay in about 47°N and 12°W. 



These examples serve to illustrate different types of annual variation 

 of temperature that may be encountered in different localities and also to 

 stress that conclusions as to the temperature variations associated with 

 processes of local heating are valid only if the data are such that the 

 influences of shifting currents and vertical motion can be eliminated. 



Diurnal Variation of Surface Temperature. The range of the 

 diurnal variation of surface temperature of the sea is, on an average, not 

 more than 0.2 to 0.3°. Earlier observations gave somewhat higher 

 values, particularly in the Tropics, but new, more careful measurements 

 and re-examination of earlier data in which doubtful observations were 

 eliminated have shown that the range of diurnal variation is quite small. 

 It can be stated that in general the diurnal variation of surface tempera- 

 ture in lower latitudes can be represented by a sine curve with extreme 

 values between 2:30 and 3 and between 14:30 and 15 , and a range of 

 0.3° to 0.4°. In higher latitudes the extreme values come later and the 

 range is even smaller. In the Tropics the Meteor observations give ranges 

 of only 0.2° to 0.3°. The Meteor and the Challenger data show that close 

 to the Equator the diurnal variation of surface temperature is somewhat 



