The surface of the earth is naturally heterogeneous with respect to its roughness, temperature, moisture and other properties. When air moves along such a surface it is modified continuously by the horizontally varying properties.
The degree of this modification depends on the amplitude and areal extent of the surface inhomogeneities as well as the prevailing large scale flow pattern. This paper describes the effects of the sizes of localized heat sources (LHS) on flow and temperature environment when the wind passes from one surface to another with different temperature. The LHS is considered to be narrow in the x flow direction and infinite in the y flow direction, and the temperature of LHS is specified to be 10°C higher than that of the other surface areas.
The nonlinear two-dimensional steady-state equations in the planetary boundary layer are constructed and solved by Estoque and Bhumralkar's model (1970), which is based on the numerical solution of the steady-state nonlinear meteorological equations for three dimensional flow. The computed horizontal velocity shows that the prevailing flow decelerates on encountering the windward edge of LHS and accelerates on leaving the leeward edge. As a consequence of the horizontal velocity variation there is an upward motion over the LHS and a downward motion downwind. The potential temperature perturbation in the atmospheric boundary layer is spread horizontally and vertically by the advection and diffusion process, and the effect of the surface heat is more marked above the downwind edge of LHS as well as over its center.
The maximum convective height can be represented as
Z_max=ζ_max⋅R^-1/6⋅l,
where Z_max is the maximum convective height, ζ_max non-dimensional maximum convective height parameter, R non-dimensional parameter, l horizontal scale of the heat island, which were used in the theory of Kimura et al. (1975). The present results indicate the maximum height of the convective layer is approximately proportional to R^-1/6⋅l. The negative temperature perturbation, “cross-over”, appears as l is greater than 500m.
As mentioned above the results indicate a significant difference in the depth of the circulation and the perturbation of temperature changes with the scale of HS, The present model gives a quantitative indication about the size, shape and intensity of the circulation due to LHS under different conditions.

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The experiment was conducted to clarify the diurnal variations of leaf temperatures of rice (C₃ plant) and Japanese barnyard millet (C₄ plant). Both plants are hygrophyte and grow under similer conditions. The rice and Japanese barnyard millet were grown in pots under flooded condition. One month after transplanting, the leaf temperatures and transpiration rates were measured under natural conditions. Solar radiation, wind speed, air temperature and relative humidity were also measured. The period of the measurements were from July 25 to July 31, 1977. The results obtained are as follows:
1) Diurnal variation of leaf temperatures of rice and Japanese barnyard millet;
The leaf temperature of rice was almost equal to the air temperature at sunrise and sunset and 0.5 to 1.0°C higher at night. However, it came below the air temperature with increasing solar radiation. The leaf temperature of Japanese barnyard millet was nearly the same as the air temperature at night. However, it went up higher than the air temperature after sunrise, and became increasingly higher with solar radiation.
2) Diurnal variation of transpiration rates of rice and Japanese barnyard millet;
There was no difference in transpiration rate between rice and Japanese barnyard millet under weak solar radiation. In the midday of high solar radiation, the transpiration rate of rice was greater than that of Japanese barnyard millet.
3) Relationship between solar radiation and leaf temperatures of rice and Japanese barnyard millet;
The temperature difference between leaf of rice and air was correlated negatively with solar radiation. The temperature difference between leaf of Japanese barnyard millet and air was correlated positively with solar radiation.
4) Relationship between solar radiation and transpiration rates of rice and Japanese barnyard millet;
The transpiration rates of rice and Japanese barnyard millet were correlated positively with solar radiation. Transpiration rate of rice was approximately the same as that of Japanese barnyard millet under low solar radiation, whereas it was higher under high solar radiation.
5) Relationship between leaf temperatures and transpiration rates;
The difference of leaf temperature between Japanese barnyard millet and rice was correlatedpositively with difference of transpiration rates between rice and Japanese barnyard millet.
Rice and Japanese barnyard millet are known to have similar geographical distributions, although the optimum temperatures for photosynthesis and growth of rice are lower than those of Japanese barnyard millet. They also share the same growing season. These facts could be, we suppose, due to the lower plant temperature of rice under high air temperature and solar radiation.

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With the purpose to obtain necessary data for constructing a simulation model for photosynthesis and primary production of rice plant in relation to meteorological environments, measurements were made on rice leaves with a leaf chamber method, of the leaf boundary layer resistance (r_a) to water vapour transfer in dependence of wind speed and also of stomatal (r_s) and mesophyll (r_M) diffusive resistances as a function of radiation intensity.
r_a was found to be proportional to the square root of the effective leaf length along the wind direction, and inversely proportional to the square root of the wind velocity, so that Sherwood number (Sh) was presented in the form: Sh=ARe^1/2Sc^1/3 with Re and Sc being Reynolds and Schmidt numbers. The proportional constant A appeared to be 0.86-0.91.
r_M responded almost instantaneously to the suddenly changed radiation levels, while r_s took a certain time before it reached a steady-state value. The transitional response pattern in r_s to an increased radiation was found to be approximated by a response function of first order lag, while that to a decreased radiation by a function of logistic type. The time constant for the opening response of the stomata appeared to be about 5min. and that for the closing response about 6min.. The steady-state value of r_s in the dark was 30-40seccm^-1 and it decreased with increasing radiation intensity in a negative exponential fashion. At short-wave radiation intensity of 0.6calcm^-2 min^-1 (=0.26calcm^-2 min^-1 in PAR, 400-700nm), r_s reached a minimum value of about 1.2sec cm^-1·r_M also decreased with the increase in radiation up to about 0.8calcm^-2 min^-1. Under a normal range of the environments, the net photosynthetic rate (P_n) was likely to be restricted more by r_M than by r_s or r_a.
A linear relation was found between P_n and the total conductivity for CO₂ between outside air and the air in the intercellular spaces, giving a support to the hypothesis (Raschke, 1975) that the stomata stabilize the CO₂ concentration in the intercellular spaces at a constant level.

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