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Volume 57, Issue 4
Displaying 1-4 of 4 articles from this issue
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Ahmed M. ABDEL-GHANY, Toyoki KOZAI, Nabil Y. ABDEL-SHAFI, Ibrahem S. T ...2001 Volume 57 Issue 4 Pages 169-182
Published: December 10, 2001
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSA dynamic simulation model for heat and water vapor transfer in a fluid-roof greenhouse was developed to study the effects of the fluid-roof and plant density on the temperatures of the greenhouse components. The greenhouse components, consisting of hollow-channeled polycarbonate roof with 1.5% CuSO4-water solution as a liquid radiation filter, plant canopy, moist soil and the inside air, were described by a system of non-linear differential equations considering the possible modes of energy exchanges among these components. The Predictor Corrector technique was applied to solve the system of equations simultaneously to predict the temperatures of these components and the relative humidity of the greenhouse air. The simulated results show that the fluid-roof greenhouse can be used without ventilation during the hot summer daytime and that acceptable plant temperature can only be achieved at low plant density. However, the greenhouse with high plant density must be ventilated during the hot summer daytime to keep the relative humidity at a normal level and to keep the plant temperature lower than the outside temperature.View full abstractDownload PDF (1702K) -
Hitoshi YOKOYAMA, Masaaki KISO2001 Volume 57 Issue 4 Pages 183-191
Published: December 10, 2001
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSLeather fern is a major horticultural plant in Hachijo Island, Tokyo and has been grown in protected cultivation. The visual damage of leather fern leaves called “Mottled Yellowing Syndrome (MYS)” has occurred on the leaves cultivated in greenhouses since 1990's. Appearance of MYS on the leaves reduces their market value.
In order to elucidate the cause of the occurrence of MYS, we investigated the environments of leather fern greenhouse by field survey and interviews with greenhouse owners. Furthermore, we measured the micrometeorology of both a greenhouse with MYS (MYS house) and a greenhouse without MYS (non-MYS house) in August 1997.
From field investigation and measurements, the following results were revealed.
(1) MYS occurred in greenhouses with low shading material and low ventilation area, which were enclosed by thick windbreaks or surrounding hill slopes.
(2) MYS occurred in poorly irrigated greenhouses with inadequate water supply and longer drought period.
(3) There were obvious micrometeorological differences between the MYS house and the non-MYS house. Light transmittances of MYS and non-MYS houses were 44% and 17%, and the ventilation-coefficient of the MYS house was 1.9 times higher than that of the non-MYS house. Air temperature and relative humidity inside the MYS house were 3.3°C and 9% higher than outside, while those in the non-MYS house were 1.2°C higher and 3% lower than outside. Soil water potentials of MYS and non-MYS houses were 0.003 and 0.023MPa, respectively.
(4) MYS of leather fern occurred in greenhouses under conditions of high air- soil- temperature, high evaporation, and low soil water contents.
(5) The low humidity around the plants could bring about water stress on the plant; thus not only the high temperature stress but also water stress or both could cause MYS.View full abstractDownload PDF (1169K) -
Reiji KIMURA2001 Volume 57 Issue 4 Pages 193-200
Published: December 10, 2001
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThis paper demonstrates the characteristics of climate in Okinawa islands and examines the factors that affect the climate and regional temperatures. The difference between the urban annual average temperature and background rural annual average temperature (ΔTyu-r) decreased with increasing wind speed and appears to be approximately proportional to the population, traffic quantity, and especially the ratio of artificial surface coverage. A strong relationship was found among the ratio of artificial surface coverage, surface temperature, and the days of rainfall from July to August.
The contribution of the artificial factor (the ratio of artificial surface coverage) to the estimated mesh temperature was examined. The calculated results of mesh temperatures, using a multiple-regression analysis with topography, latitude, and the ratio of artificial surface coverage, indicated that the artificial factor greatly affects the estimated mesh temperature over the Okinawa islands. The annual average sensible heat flux was calculated using the value of ΔTyu-r. The results of the calculation agree well with estimated values using a heat balance model.View full abstractDownload PDF (1065K) -
Nas-Urt TUGJSUREN, Tamio TAKAMURA2001 Volume 57 Issue 4 Pages 201-207
Published: December 10, 2001
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThis article discusses common features of photosynthetically active radiation (PAR) in the Mongolian grain farm region during the period of 1986 to 1996. The quantitative characteristics of solar radiation, such as direct, diffuse and global radiation are evaluated in the study through the long term trend.
The mean pattern of seasonal variation of PAR shows that the yearly minimum global (direct+diffuse) PAR is 68.9±7.6MJ/(m2 month) in December while the maximum is 307.5±10.3MJ/(m2 month) in May. The yearly summation is 2.22±0.07GJ/(m2yr) and is very stable compared with monthly variations.View full abstractDownload PDF (796K)
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