AIR TEMPERATURE 
Although a study of air temperatures at sea, and a 
consideration of differences between sea-surface andair 
temperatures is of great importance in problems of 
evaporation, condensation, and precipitation in oceanic 
regions, a few temperature observations made during 
short periods over extensive reaches of ocean surface 
can be expected to have little climatological significance. 
With these facts recognized, the discussion of air tem- 
peratures in this section of the report will be curtailed 
and only the more important features and relations to 
other elements will be mentioned. The temperature re- 
lations between sea surface and atmosphere will be dis- 
cussed in greater detail in the chapter on sea-surface 
temperatures. 
The eighteen main groups into which the Carnegie 
air-temperature data have been divided are not present- 
ed as separate and distinct climatological regions, but 
merely as convenient devices for facilitating the discus- 
sion of such data. 
Mean Air Temperatures for Groups 
The mean hourly values of air temperature for the 
various groups are presented in tables 17 and 18. These 
mean values seem to indicate that air temperature is 
largely a function of latitude. No doubt if the individual 
groups were smaller, it would be possible to show mi- 
nor variations in the mean temperatures which were the 
results of ocean currents or of certain continental in- 
fluences. It may be observed, however, that the mean 
17 
air temperature for the Tuamotu Island Group (27°85) 
is considerably higher than the mean temperatures for 
the Coastal Peru and West Callao Groups (20°31 and 
23°96, respectively), which are in approximately the 
same latitude. Obviously the mean air temperatures of 
the latter twoGroups are greatly affected by the cold 
Coastal Peru Current. Similarly, the California and 
Japan Groups present mean temperatures lower than the 
mean temperatures for their latitudes because of the 
effects of the California and Oyashio currents. 
Variation of Mean Air Temperature 
with Latitude 
Data concerning the mean air temperatures for the 
various latitude ranges are presented in figure 14. It 
may be observed that the mean air temperature increas- 
es rapidly from mean latitude 45° to mean latitude 10° 
north, and that there is then a decrease toward the equa- 
tor. Evidently air temperatures between latitudes +5° 
are greatly influenced by the low sea-surface tempera- 
tures encountered by the Carnegie within this range of 
latitude. 
The air temperature-latitude curve in the Southern 
Hemisphere presents a somewhat similar profile al- 
though, in contrast with conditions in the Northern Hem- 
isphere, the mean temperature falls off very slowly be- 
tween mean latitudes 10° and 20° south. This apparent 
condition was no doubt brought about by the plan of ob- 
taining temperatures in this region -- the Carnegie re- 
Table 19. Difference between temperature readings in degrees centigrade of Hartmann and Braun 
instruments on deck and on crosstrees for ten days when sky was overcast (particularly 
during midday hours), Carnegie, 1928-29 
Day Local mean hours 
| 1-2 | 2-3 | 3-4 [4-5 | 5-6 | 6-7 | 7-8 | 8-9 [9-10 | 10-11 [11-12 
1 
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2 1.4 1.1 1.1 0.9 1.4 0.8 
2 1.6 1.3 1.0 0.9 1.0 0.3 
8 0.8 1.4 0.9 1.2 1.2 0.8 
4 1.3 1.3 1.1 1.4 0.8 0.9 
3 1.6 1.4 1.3 1.6 1.0 1.1 
3 1.7 lei 1.4 1.0 1.3 0.6 
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| 17-18 | 18-19 | 19-20 | 20-21 | 21-22 | 22-23 | 23-24 
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