The distribution of nocturnal cooling above snow was observed over a wide area on the plateaus with shallow valleys gently sloping from the Shikotsu Caldera to the Ishikari-Tomakomai Lowland in Hokkaido Island (Fig. 1), and the mechanisms of radiative cooling were induced in a shallow valley and on a plateau by comparing the temperature distribution with the cooling process at three stations.
The same extent and simultaneous cooling occurred everywhere in the valley bottom B as shown in Fig. 2. This fact proved that so-called cold air inflow played little role in nocturnal radiative cooling, though weak down valley winds were observed. The same conclusion (Tanaka et al., 1983) was induced because the cooling process went on simultaneously in a valley and on a flat plateau on clear and calm night.
Along the gently sloped plateau A on clear and calm night, the air temperature increased by 1°C with increasing altitude by 20m as shown in Fig. 3.
The potential temperatures at the lower part of the plateau A were close upon those at the bottom of the valley, which were estimated at those of extreme cooling in this area on clear and calm night.
The potential temperature at the higher points on the plateau A was close upon that at the top of inversion layer on the lowland as shown in Fig. 5. These temperature profiles suggest that because the depth of inversion layer decreased with increasing altitude of the plateau, the cooling rate of the surface layer decelerated.

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Effects of dew condensation on plastic film on the air temperature in the greenhouse or cultivation tunnel were examined by a simple heat insulating experimental box. The box is 50×50cm and the depth is 15cm. In the first experiment the upper part of the box is covered by Air-Cap which is widely used for packing. An arbitrary amount of water was injected to air bubbles of Air-Cap and the emissivity change due to water injected was evaluated. In the second experiment polyethelene film was used. Changes in emissivity of the film cover and temperature inside the box due to dew condensation were obtained by field observation in clear nights and by using heat balance equations at the polyethelene film cover and the bottom of box.
The experimental results showed that the emissivity of Air-Cap linearly increased with increasing in the watered area when the water film thickness was enough. The change in emissivity of wet polyethelene film cover due to dew condensation in the field was expressed as follows, using dry film emissivity (ε₀) and total dew amount (ΣWg/cm²).
ε=ε₀+(1-ε₀)exp{-(C₃/ΣW)²}
where C₃ is a constant and the value of 2.0×10^-3g/cm² was obtained. It is shown from the formula that the emissivity of film cover rapidly increases as the dew condensation exceeds about 3mg/cm².
Following results were obtained from the observation and heat balance analysis. As the emissivity increases, the temperature of film decreases, while the temperature of the bottom of box increases because a wet film obstructs the radiation loss to the atmosphere. Then both temperatures gradually approach to the same value with the increase of the dew amount. When the emissivity of film cover becomes unity, the film and the bottom have the same temperature.

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Because in summer the outside air temperature in many Asian countries is too high to grow certain flowers and vegetables, these crops are often grown in a greenhouse which is cooled by cooling equipment. For example, the development and growth-rate of carnation, roses and melons can be improved by using both daytime and nighttime cooling.
In this paper cooling load of a single span greenhouse in summer nighttime is investigated. The experiments were made under the following three different thermal screen conditions:
1) two thermal screens open
2) one thermal screen closed
3) two thermal screens closed.
The greenhouse was cooled by a heat pump that was in operation continuously during the night, and no crop was present in the greenhouse. The results can be summarized as follows.
(1) Under the condition of a constant inside air temperature the cooling load of the greenhouse is due to
1) air infiltration Q_v 42%
2) soil heat flux Q_s 38%
3) overall heat transmission Q_t 20%.
(2) An empirical relation for estimating air infiltration rate of the cooled greenhouse V_g was proposed. In the relation, V_g is a function of the outside wind speed and the air temperature difference between inside and outside the greenhouse. With wind speed being 1m/s and the temperature difference ranging from 3 to 15K, the value of V_g ranged from 1.5 to 3.0m³/(m²hr).
(3) From measurements it appeared that 70% of the whole heat transfer due to air infiltration Q_v was caused by the transfer of latent heat. Because of this result Q_v was proposed to be described as being proportional to the enthalpy difference between inside and outside air instead of temperature difference. Q_v decreased to 63% with one thermal screen closed and 58% with two thermal screens closed.
(4) The effects of thermal screen on the heat transmission h_t [kcal/(m²hr K)] were:
1) thermal screen open: h_t=1.62
2) upper thermal screen closed: h_t=1.20
3) lower thermal screen closed: h_t=0.51
4) two thermal screens closed: h_t=0.50
The upper thermal screen was an aluminium powder mixed polyester film with a thickness of 0.05mm. The lower thermal screen was a polyethylene film of 0.05mm thick.
(5) The process of greenhouse cooling is considered to be a first order process of which the time-constant is estimated by parameters of the greenhouse and the cooling system.
Based on this assumption it is proposed that two definitions of the maximum cooling load of a greenhouse are possible, the one is static and the other is dynamic. The static conception is used in the case the heat pump or any cooling equipment needs continuous operation for keeping a setpoint air temperature. In this case the cooling load of greenhouse is equal to the capacity of the cooling equipment. The dynamic definition is used in the case the capacity of the cooling equipment is so high that no continuous operation is needed to maintain a setpoint air temperature.

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In order to develop a continuous measuring method to detect both soil moisture and electric conductivity, experiments were conducted to increase the accuracy of soil moisture measurements by the thermal method.
It is the most important factor for this method that soil water movement induced by temperature gradient around the heat source should be neglected. Also, heating capacity and time in the heat source should be determined at designed certain values. Suitable heating capacity and time were 0.8 Watts and 15 minutes, respectively, in volcanic ash soil, sandy soil, and 0.2mm glass beads.
In the case of decreasing contact surface of heat source body with soil, especially sandy soil, the heat transfer coefficient tended to lower. Therefore, it was necessary to increase contacting surface of the heat source body and to improve its form.
Concentration of electrolytes: less than 0.01M KCl solution, in soil water did not affect to detect soil moisture and rising temperature in the center part of cylindrical heat source body.
As the rising temperature of the heat source decreased with rising soil temperature, we revealed that soil temperature compensation value (alpha) in the equation (θ₀=θ/1-α(Θ-Θ₀)) is 0.0051/°C in the volcanic ash soil.
The correlation coefficient between pF values and rising temperature of the heat source was 0.89 for non-compensation values; an application of this equation to the same data gave it 0.97.

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This report describes the assessment of the total net primary production (TNP) in Japan. TNP for the respective prefectures and for the whole country was estimated from
TNP_i=Σ⁴_j=1A_ij⋅E_j⋅NPP_i
TNP₀=Σ⁴⁷_i=1TNP_i
where TNP_i and TNP₀ denote, respectively, TNP for the i-th prefecture in Japan and the whole country, A_ij is the area of the j-th land class in the i-th prefecture, E_j is the production efficiency of the j-th land class, NPP_i denotes the average of net primary productivity of natural vegetation of the i-th prefecture.
The geographical distribution map of NPP presented in a previous paper (Uchijima and Seino, 1985) was used to obtain the values of NPP_i. The following values proposed by Matsuda et al. (1982) were used as E_j:
j=1 forest lands E₁=1.0
j=2 fruit tree lands E₂=0.80
j=3 cultivated lands E₃=0.81
j=4 grass lands E₄=0.625
The land area A_ij of the j-th land class in the i-th prefecture was evaluated using the statistical data of land utilization in Japan (1980).
Table 1 summarizes the assessment of TNP_i and TNP₀. NPP_i increased from about 10t DW/(ha yr) in Hokkaido to about 20t DW/(ha yr) in Okinawa prefecture. This is mainly because climatic resources for primary production are more plentiful in Okinawa prefecture than in Hokkaido. Table 1 also shows the prefectural variation in energy efficiency (ε) of TNP_i on the basis of annual global solar radiation (S_t) and photosynthetically active radiation (S_par), and on the basis of the respective radiations (S_{t, 10} and S_{par, 10}) for the plant growing period (T_a≥10°C). Although ε of TNP_i on the annaul amount basis in Okinawa prefecture is about twice as large as that in Hokkaido, ε of TNP_i in Hokkaido on the basis of radiation amount for the plant growing period is larger than that in Okinawa prefecture.
Fig. 1 shows the comparison of TNP_i obtained in this report with the results estimated by Iwaki (1984) using a plant ecological method. The points are well distributed around 1:1 line, indicating that there is a good agreement between them.
Table 2 shows the comparison of TNP₀ for the whole country of Japan presented by several researchers. TNP₀ in Japan was assessed to be 380Mt DW/yr by Chikugo model, agreeing well with the results of Iwaki (1981, 1984), Murata (1981) and Matsuda et al. (1982) by plant ecological method.
Fig. 1 and Tables 1 and 2 give a strong support to the validity and applicability of the Chikugo model based on theoretical considerations of fluxes of water vapor and carbon dioxide due to transpiration and photosynthesis.

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