Abstract
In order to analyse the relationship of air temperature to the growth of crops, the classificatory constitution of air temperature during the growth stages of crops should be clarified. But the assumption of such classification from the recording paper is troublesome and collection of recording papers from various places is difficult. From these reasons, the writer tried to obtain the classificatory constitution by calculation through the typification of diurnal variations of air temperature.Assuming that θmin shows minimum air temperature and that R represents diurnal range of air temperature, θt showing air temperature at the time of t becomes as follows:θt=θmin+atR (1)where at is the coefficient of diurnal range of air temperature. Through the same procedure, θ0 showing mean daily air temperature follows asθ0=θmin+aDR (2)where aD shows the average of at.The average air temperature θm otained from the daily maximum and the minimum is as follows:θm=θmin+0.50R (3)From formulas (2) and (3) aD is obtained:aD=0.50-Δθ/R (4)where Δθ=θm-θ0.The monthly average values of aD calculated from (4) by use of the data from the main stations in Japan are shown in Fig. 1.The distribution of annual variation of aD classified as A1, A2, B and C types is shown in Fig. 3. The average aD ranging from May to August becomes 0.45 in Japan (Fig. 3). By drawing both diurnal variation curves of air temperatures having various aD values (Fig. 4) and the curve (C-curve) put the case that the emergence times of the maximum and the minimum points on a sine-curve are distorted as 5a.m. and 2p.m., Δt showing the difference of emergible time more than constant at obtaind from both diurnal variation curve of air temperature having certain aD value and C-curve was obtained (Fig. 5). Δt was ascertained to be -1.3 hours in the case of aD=0.45 and at=0.1-0.9. As the emergible time of C-curve at the case of more thanconstant at value is equal to the case of sine-curve, it is probable to obtain the emergible time by the calculation and the curve for aD=0.45 can be obtained by adjusting Δt, -1.3 hours (Fig. 7, S-curve). An example for the diurnal variation S-curve of air temperature was shown in Fig. 4 (full line). Such S-curve will be taken as a typical diurnal variation curve of air temperature during summer season in Japan. By using S-curve, the emergible times of classificatory air temperatures will be easily obtained from Fig. 6, when the air temperature is substituted by at in a formula (1).
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