INFLUENCE OF THE REGIONAL CLIMATE ON THE CLIMATE IN THE GREENHOUSE, WITH PARTICULAR REFERENCE TO THE MEDITERRANEAN REGIONS
A greenhouse is composed of an external covering (of various materials-glass or plastic) together with its system of heating, humidification and ventilation. The energy balance of a crop in the greenhouse may be expressed by reference to the energy balance of the same crop in the open. Except for water, which is practically never a limiting factor in greenhouses where irrigation close to the potential evapotranspiration requirements is used, the important modifications are:
- on the balance of radiation exchange in the solar spectrum and the infra-red region (greenhouse effect). Regarding this effect, the differences observed are functions of the regional climate, of the structure of the greenhouse and the differences netween the interior and exterior temperatures.
- on the turbulence near the crop. By the use of any of the conditioning systems employed (thermosiphon or forced ventilation, for example) this turbulence is reduced compared with that in the open.
The Mediterranean climate, having high insolation throughout the year and occasional violent winds, serves to demonstrate the strong dependence of the climate in the greenhouse on the external conditions.
The choice and eventual development of protective structures and acclimatization techniques must therefore take into account this dependende of the microclimate of the