Abstract
As a preliminary to the study of microclimatic conditions in a glass or vinyl house, comprehensive measurements were made in a closed glasshouse of Natl. Inst. of Agric. Sci. during a relatively long period from Nov. 1966 to April 1967. Ten ventilated nickel resistance dry and wet bulb thermometers were used to measure temperature and humidity in the glasshouse. The data used in this paper were extracted from the charts by visually determining 30-min, means. The results obtained may be summarized as follows:
(1) The diurnal change of temperature inside the glasshouse was in phase that of the air temperature measured at the height of 130cm in the enclosure. This was mainly due to the small heat capacity of the glasshouse.
The difference in the maximum air temperatures between inside and outside the glasshouse increased proportionally with increasing solar-radiation. This relationship may be used in predicting the maximum air temperature inside the glasshoue from the climatic data of air temperature and of solar radiation
(2) The minimum temperatures inside the glasshouse were almost always about 1-2°C higher than those measured at the enclosure. The difference of the minimum air temperatures between inside and outside the glasshouse reported by YABUKI (1961) was slightly larger than that presented in this paper. On comparison, the results from a simple conventionl way (iTmax+iTmin)/2 turned out to be larger by about 10 percent than those calculated from thirty minutes averages.
(3) The fall of air temperature inside the glasshouse during the night was found to be closely related to two factors of the night fall of the outside air temperature and of long-wave net radiation. The temperature of inside surface of the glass was estimated by a radiation balance equation in the glasshouse. From the results it followed that on a clear night the temperature at inside surface of the glass wall was lower by about 6-7°C than that of the floor surface in the glasshouse, implying that the temperature at the inside surface was equal to the air temperature outside the glasshouse.
(4) An equation relating air temperature conditions in a glasshouse to outside meteorological conditions and to the glasshouse structure was obtained by considering heat balance of the glasshouse. The daily mean and daily amplitude of the air temperature inside the glasshouse were compared respectively with empirical relationships obtained in this report.
