| Budget Amount *help |
¥6,800,000 (Direct Cost: ¥6,800,000)
Fiscal Year 1990: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1989: ¥5,000,000 (Direct Cost: ¥5,000,000)
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| Research Abstract |
Locality in distribution of low temperatures which appear in complex topoqraphy such as basin and slope lands become conspicuous under the condition of radiative cooling and are featured by the inversion of air temperature. In those situation, there are dowm stream along the slope, but there are big difference in explanation of thermal characteristic of down stream. Those difference give great confusion to controling methods for frost damages. The authors framed a hypothesis for down stream. "The thermal action of down stream to thermal environment of lower part of slope changes with time, and lt acts as cold air drainage around sunset but acts as inhibitor for cooling of radiative cooling in the period from mid-night till dawn." In order to make clear the hypothesis and mechanism of radiative cooling, we conducted measurements of microclimate using infrared image analyzer and meteorological observation system in the sloped tea garden in Ube City, Yamaguchi Prefecture. From the experim
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ents, we found that our hypothesis was good, and down stream inhibited to cool in the most imoprtant period after midnight. Then, from the experiments and simulation analysis for cooling of land with mosaic like surface, we made clear that difference in the heat capacity and the thermal diffusivity of soil of surface substances effected grade of cooling for surface temperature and air temperature near ground surface. For example, the surface of semicylidrical tea plants became source of cooling by insulating heat flow from ground soil. In the comparison of air temperatures above ground between the bare road run vertically and the rows parallel to the slope at same level of the slope land, air temperature became higher in the road run vertically, where down wind speed was higher. We confirmed air temperature cool down more in the place where wind become weak.
We detected the phenomenon of role typed convection in the distribution of surface temperature over the slope land firstly in the world. The cause or mechanism of these phenomena, however, has yet to be sufficiently clarified. It largely depends on new measurement instruments and future multilateral studies. Less
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