One of the important problems in local cliniatology concerning the air temperature distribution is a study of the diurnal change within a small area in which various land forms and covers are included. Actually, the results of the, observations show that the differences of the diurnal change are not shall as shown 1 and 2. (The situations of the observed points in this area are shown in Tab. 1) To discuss the detail of this dif-ference, it is considered that a statistical treatment must be helpful for us. So the author applies the conception of turbulence in a statistical theory as a method of comparison of the diurnal changes in a small area.
The definition of degree of turbulence in our study is not the same as that of the micro-meteorology, and is described as follows; A. B, …………, N are the observed points in a small area, i, (1+1), (i+2), …………, (n-1) n the observed times, and if the air temperature at A observed on the thermograph at time i is Ai, the average change in a small area from i to (i+1) will be expressed by
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And its standard deviation oi•(i+1) is calculated for the expression of variance of air tee iperature change from i to (i+1). If the values at each station change in parallel, “ai”(i+1) becomes O. We define δi•(i+1) as a degree of turbulence in a small area from the time i to (i+1), δ(i+l)•(i+2), δ(i+2)•(i+3), ……, δ(n-1)•n are also calculated in the same way. For instance, the remits of the above mentioned case are shown as Fig. 3. Time intervals i_??_(i+l), (i+1)_??_(i+2), ……… must be determined by the accuracy of the thermograph, the time necessary for a airmass passing through the whole, area and the movement from a point to the next on the moving observation if ti'e reduction values are required for the values taken by the observation, In the case of short time intervals, the following δi_??_j, δj_??_k, ………… are, : calculated
: _??_
These values are used not only for the general view of the diurnal variation. of a, but also for the calculation of “intensity of turbulence” in whole observed area. Tab. 2 and Fig. 4 (D) are the results of the calculation using the upper formula for the above mentioned area. Fig. 4 (A)_??_(C) are the results for another area in the same way of calculation and Tab. 3 is their conditions. Analysing them with special reference to the effects of Topography on each curve, the following conclusi-ons are obtained. Namely, the degree of turbulence in a small area in fine weather and with weaker winds are;
I) Greater in the daytime especially at noon. The values are 2_??_3 times as large as those at night.
II) Greater after sunrise, before sunset, or when a cold airmass flows down as down slope wind or mountai n wind. A. remarkable case occurs where the time of sunrise is greatly disturbed by the topography, e. g. Fig. 4(C) and (ID.).
III) Smaller with the greater wind velocity in a simple topography.
IV) More affected by the difference of the topographical condiction at each point than by the extent of the observed area.
