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PACIFIC SCIENCE, Vol. XVII, October 1963 
Fig. 7. Annual mean daily temperature range (°F) in Hawaii. 
fate as catalyst. The photochemical method is 
accurate enough for general agricultural pur- 
poses (Chang, 1961). Apart from the direct 
effect on local climate and plant growth, the 
radiation data could be used for assessing yield 
potential, estimating irrigation water needs, 
directing fertilizer practices, etc. (Borden, 1940). 
Figure 8 shows the distribution of mean daily 
radiation in Hawaiian sugar plantations. Maui 
has the highest radiation. Pukalani, in central 
Maui, receives 607 langleys/day or over 220,000 
langleys/year. This is exceeded only by a very 
few desert areas in the world (Budyko, 1958). 
The average radiation for the cane-growing 
areas in Hawaii is in the neighborhood of 510 
langleys/day, well above Houghton’s (1954) 
estimate of 415 langleys/day for the land areas 
in the latitudinal zone 0°-20° N. 
In Hawaii the minimum radiation is recorded 
in December, while the maximum is usually in 
June or July. The maximum monthly radiation 
is about 15% higher, and the minimum some 
2 5 % lower, than the annual mean. Radiation in 
December is about two-thirds that of June or 
July- 
SECULAR CLIMATIC CHANGES 
Since the cause for climatic variation in Ha- 
waii is rather uniform, and since the leeward 
stations in particular are sensitive to circulation 
regimes (Landsberg, 1951), the climatic change 
at Makiki, in Honolulu, can be considered to 1 
illustrate that of the islands in general. 
The average daily radiation at Makiki in- 
creased some 10% from 491 langleys/day in 
the 1930’s to 544 langleys/day in the 1950 s 
(Fig. 9). The rising trend probably started in 
1936, but records before 1932 are not available. 
