During three seasons (1965, '66 and '67) of corn plants, as part of a wide-ranging study of problems on energy and mass transfer within plant communities, comprehensive measurements of CO₂ environment within a corn canopy were made with an infrared gas analyzer (Toshiba-Beckman IR-215) at Kitamoto experiment station near Tokyo. Ten-minute observation was carried out at an interval of about 1-hr over the period from 0600 to 1900. The gas analyzer was alternetely supplied with air from nine heights within or above the canopy. In this paper, the data obtained in 1966 are mainly presented.
The absolute concentration of CO₂ in the air immediately above the canopy has a clear diurnal cycle (daytime depression). The depression of CO₂ -concentration increased with the leaf area index and finally reached about 100PPM at the time of LAI=4.2. Namely the absolute concentration decreased drastically from 370PPM at early morning (0600) to 270PPM at the time of southing (1135). It was also found that the depression is strongly affected by wind and radiation intensity above the canopy.
By making reasonable assumptions, the following expression was obtained as to the daytime CO₂ -cycle.
C_c(t)=C_a+P_s/D_a-P_N0/D_asinωt,
where C_a and C_c are the CO₂-concentration at a reference height at which no CO₂-cycle is observed and the mean CO₂-concentration in the canopy, respectively, P_s the soil respiration intensity, P_N0 the net assimilation intensity of the community at the time of southing, D_a the integral exchange coefficient in the air above the canopy, ω=π/T the time angle for the cycle, and T the period of the cycle. Model computation shows that the depression decreases with the integral exchange coefficient, agreeing well with those presented in Fig. 1.
The smooth curves of Fig. 4 were drawn to show the diurnal change in CO₂ -profile shape. The change in absolute conentration was largest in a lower part of the canopy. CO₂ decreased with height from the soil surface upward showing that the soil was behaving as a source. From 0700 to 1700, concentration decreased with the depth of the canopy, suggesting the downward flux CO₂. CO₂-profile displacement to the right after dark reflects accumulation of CO₂ in the lower part of the canopy due to the release of CO₂ from leaves and soil. The height of minimum concentration shows the diurnal cycle clearly. Although the height was near the top of canopy at early morning and evening, it decreases with radiation intensity.
CO₂-profile was approximately calculated from the following relation:
C(z)=C_H-∫^H_z{P_H-∫^H_zdF/dz(p∝I/a+bI-r_p)dz/K(z)}dz,
where C_H and P_H are respectively the concentration and the flux at the top of canopy, K(z) the profile of turbulent diffusivity in the canopy, p∝, a and b the parameters in light-photosynthesis curve, I the radiation intensity, and r_p the leaf respiration. Model computation was made to show the influence of canopy structure, radiation intensity and soil respiration on CO₂-profile shape (Figs. 6, 7 and 8). CO₂ profiles computed for the canopy with F_t=4 and k=0.5 were found to be in relatively good agreement with those in the corn canopy. Particulary, the diurnal cycle of the height of minimum concentration coincides well with that observed in the canopy. The height (z_m) was found to gradually decrease with displacement of the maximum level of leaf area density downward.

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The equation of heat-transfer on the spherical thermometer bulb can be expresed in a dimentionless form:
Nu=β+KReⁿ. ……(1)
where, β=(2Hr/k+2), H is the radiative heat-transfer coefficient, k the molecular heat conductivity of the air, r the radius of the thermometer bulb. The Nusselt number is usually written as
Nu=KReⁿ. ……(2)
The time constants of two types of mercury thermometer were measured in a wind tunel, and the Nusselt number for each thermometer is computed from Eqs. (1) and (2), respectively. The values obtained from Eq. (2) have slightly a different tendency from those obtained from Eq. (1) as shown in Fig. (3).
This difference arises from the effect of radiative heat-transfer. The measured lag of the thermometer is also affected by radiative heat transfer. So as we express the Nusselt number with the lag as
Nu=2r/k(1/αMC/S-H), ……(3)
where α is the time constant of the thermometer; M, C, and S are mass, specific heat, and surface of the thermometer bulb, respetively.
Substitutiug Eq. (3) into Eq. (2), it becomes equal to Eq. (1) in the expression. From the measurements the values of constants for the spherical thermometer are: K=0.40, n=0.5.
Empirical formulae of the Kata-thermometer are examined with equation, and the result agrees well with the values shown in Table 1, which suggests applicability of Eq. (1).

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This paper is prepared for giving climatological information on hail occurrence in Japan. It is pointed out that there are two kinds of maxima in the distribution of the number of hail days in Japan. The maxima along the coast of the Sea of Japan are attributed to hailstorms mostly occurring in the cold season, (October-March), Whereas inland maxima are mostly due to hail in the warm season (April-September). Observational records of 4 selected weatherstations, 2 in one of the west coast maxima and 2 in one of the inland maxima, are examined in detail. It is found that cold season hail occurrence shows practically no diurnal variation, but warm season hailstorms occur mostly in the afternoon through the evening hours. Warm season hailstorms are almost always associated with thunderstorms, but there are many cases of hailstorms without thunderstorm in the cold season. Some other features of interest on hail in Japan are also described.

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This paper presents the results obtained from the statistical analysis of summer climate conditions in relation to the growth and the yield of rice crops. The climatic data used here were the yearly series (1889-1965) of mean air temperature for its vegetative period (July to August) at fourty stations. From these yearly series of the temperature were determined the coefficients of variation, return period, autocorrelation coefficient and spectrum distribution, respectively.
The obtained results may be summarized as follows:
1) Deviations of the July-August mean air temperature from the normal were fairly large in the estern part of Hokkaido, that is, the value-of coefficient of variation (C. V.) reached about 9% in this part, while the values of C. V. in south-western part of Japan were less than 3%. These results seem to indicate that there is difference in the stability of summer climate between both regions.
2) Return period (R. P.) of the July-August mean air temperature was determined by an empirical way. The mean air temperature for a most recent year with the cool summer damage of rice crops was adopted as a climatologically critical temperature for the occurrence of the cool summer damage at districts concerned. In Tohoku region the critical temperature has been reduced by 1-2°C on accont of the marked improvement on the cultivating technique since 1955. However, the critical temperature in Hokkaido district has hardly been lowered, although improved agricultural technique has widely been adopted to reduce the direct influence of weather conditions upon rice crops. It was found that the probability of being damaged by cool summer is still so high as its return period is 2.5 years.
3) Correlograms of yearly series of the July-August mean air temperature showed the high stability of the climate in the southern part of Kyusyu and Shikoku, while in the eastern part of Hokkaido the values of R(t) decreased rapidly with lag time, which show the large variability of temperature in summer. The shapes of correlograms in the other districts except for Hokkaido were too diversiform to interpret the variation of temperature.
4) Spectral analysis of both the yearly series of summer temperature and of the rice yield in Hokkaido and Aomori Prefec. was done with an electric computer (TOSBAC-3400). The peak of the spectral densities in both the series did not satisfactorily agree with each other. Periodicity of the air temperature was not so clear as found by Ozawa et al. (1952), mainly because the yearly series of the air temperature was not enough in the length to find statistically the pronounced periodicity.

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The influence of shape and volume of the small tunnel-like covering on the inside temperature was studied. Results obtained are summarized as follows.
(1) Temperatures of air, soil surface and soil in the covering go down with the increase of the height of covering under conditions that covered areas are the same.
(2) Air temperature in the covering with a small β(=surface area of the covering/volume of the covering) was higher than that in the covering with larger value of β.
(3) Soil temperature, in the covering with a larger covered area was higher than that in the covering of a small covered area.

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