Co-Authors:
Cohen, Y., Division of Agricultural Meteorology, Institute of Soils and Water, ARO, Bet Dagan, 50 250, Israel
Stanhill, G., Division of Agricultural Meteorology, Institute of Soils and Water, ARO, Bet Dagan, 50 250, Israel
Fuchs, M., Division of Agricultural Meteorology, Institute of Soils and Water, ARO, Bet Dagan, 50 250, Israel
Abstract:
The results of an experimental study are presented, in which the reduction of air and surface temperatures within a glasshouse induced by evaporative cooling of the outer roof was compared with that brought about by wetting the top of the canopy and soil surfaces. The experiments were carried out in a naturally wind-ventilated multispan Venlo glasshouse in the high-radiation environment of southern Israel. The difference between the air temperature inside and outside an uncropped glasshouse was found to be linearly related to the global solar radiation flux incident on the glasshouse roof, so that the temperature differential increased by 0.015°CW-1 m-2. Wetting the upper surface of the roof, or the soil surface, reduced the solar air heating to 0.0067 or 0.0016°CW-1 m-2, respectively. The combination of wetting the roof and the soil surfaces reversed the relationship to - 0.016°CW-1 m-2. In a glasshouse with a growing tomato crop, temperature differences between the air inside and outside of the glasshouse were affected similarly by the wetting treatments, although to a lesser degree. With growing plants, or wet soil surfaces, evaporative cooling of the roof surface appeared to have a minor effect on glasshouse air and foliage temperatures. These temperatures, however, were strongly affected by evaporative cooling of soil and foliage surfaces. Direct evaporation of a water droplet suspended in a spray mist in the air appeared to be the most effective site for evaporative cooling of the glasshouse. © 1983.
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