HUMIDITY 
49 
Table 58. Frequencies of hours of occurrence of minimum relative humidity, Carnegie, 1928-29 

Local mean hours 


TOU 
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vi 
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vil i... ia sy NE AGS ahs Fao Siac Ne 5. tee ay 2 Ma 
Meese ed ics, Wey ce Uae) ate oop cian cepa oe Be 
ome ce ee igh 20S 31 ae ae 
Se tt 1d 8 i 4 8, rT eT 8 8 ee ee 
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xi 
(} 2 ewer vier tar /Gtt ath 4, 5) Ms eae 1 1 
i < ae teat 21 ed 2° Ree nes 
xIV re Mes Wer Sh eR A oa i Beier ay wh 
Xv 4 4 ioe ae ta GA el ay a CTC het ee 
XVI es ae ae ey he ee ee ap eT 

Wotaleigsii = 5 9 -8 8 4 10 
8 16 37 45 52 63 53 44 33 24 13 13 7 8 1 8 

Table 59. Frequency distribution of the 
unperiodic diurnal amplitude of relative 
humidity, Carnegie, 1928-29 
Range in No. |P af ee Cumulative 
per cent days eis percentage 
< 5.0 7 2.3 2.3 100.0 
5.0 - 10.0 106 34.7 37.0 97.7 
10.0 - 15.0 120 39.2 76.2 63.0 
15.0 - 20.0 53 17.3 93.5 23.8 
> 20.0 20 6.5 100.0 6.5 
Total 306 MED edokcno — “enodaina 
what higher value for relative humidity at this hour. 
Otherwise we should expect the hour of maximum rela- 
tive humidity to coincide with the hour of minimum air 
temperature (05h). 
Variation of the Diurnal Amplitude of 
Relative Humidity with Latitude 
Data concerning the variation of the diurnal ampli- 
tude of relative humidity by ranges of latitude are shown 
in table 60. It is an interesting fact that the variability 
of relative humidity between mean latitudes 10° and 40° 
north is a constant (12 per cert). Such a result may be 
partially explained on the basis of the fact that the 
curves of variability of air temperature (fig. 18) and va- 
por pressure, according to ranges of latitude, are com- 
pletely out of phase between these ranges, whereas they 
tend to approximate the same phases in the Southern 
Hemisphere. 
Effect of Wind on the Diurnal Amplitude 
of Relative Humidity 
As has been done in the cases of air temperature 
Table 60. Mean unperiodic diurnal amplitude of relative 
humidity for ranges in latitude, Carnegie, 1928-29 
Range in | Mean in| No. Range in} Mean in| No. 
latitude | per cent|days latitude | per cent |days 
>45 N 8 27 5N- 5S 11 34 
45 N-35 N 12 26 9S-158 12 37 
35 N-25 N 12 40 15 S-25 S 12 31 
25 N-15 N 12 32 25 S-35 S 14 24 
15N- 5N 12 46 35 S-45 S 11 9 
Mean and total _............. 12 306 
and vapor pressure, the mean unperiodic amplitude of 
relative humidity has been computed for fifty-two days 
in tropical regions between latitudes 20° north and 20° 
south; with a wind force equal to or greater than 4, 
Beaufort scale, and for fifty-two days with a wind force 
less than 4. The results give a diurnal amplitude of 9.96 
per cent for days with wind force equal to or greater 
than 4, and one of 12.85 per cent for days with a wind 
force less than this value. This result compares favor- 
ably with the results of similar treatment of air-tem- 
perature and vapor-pressure data, that is, higher wind 
velocities tend to reduce the diurnal amplitudes of all 
three elements. 
Harmonic Analysis 
of Relative-Humidity Data 
As shown in table 61, the amplitudes and phase an- 
gles of the 24-hour, 12-hour, and 8-hour terms are ex- 
tremely irregular between the various groups of Carne- 
giedata,as was also found to be the case with vapor pres- 
sure. The time of minimum air temperature and vapor 
pressure, however, and the time of maximum relative 
humidity, appear to occur with considerable regularity, 
the maximum relative humidity occurring between mid- 
