pouvoir évaporant de l'air

CONT: Le pouvoir évaporant de l'air ne dépend que des caractéristiques de l'air : déficit de saturation et vent. Il peut être exprimé par le terme Ea figurant dans l'équation de Penman et estimé à partir de l'évaporation mesurée sous l'abri météorologique.

CONT: Crops grow reasonably well with widely different amounts of water in the atmosphere but when the air immediately surrounding the leaves becomes too dry, growth will be checked. If there is an adequate amount of water in the soil, supplied either by rain or irrigation, the plants can ordinarily absorb and transpire enough water to maintain a moderately moist atmosphere around the leaves, but when soil moisture is deficient and the evaporating power of the air is high, water will be lost from the leaves faster than it can be obtained from the soil and the plant will wilt and be unable to grow efficiently. Thus, the dryness of the air as well as the dryness of the soil is likely to limit crop production.
CONT: The only factors affecting ET[subscript o] are climatic parameters. Consequently, ET[subscript o] is a climatic parameter and can be computed from weather data. ET[subscript o] expresses the evaporating power of the atmosphere at a specific location and time of the year and does not consider the crop characteristics and soil factors. The FAO Penman-Monteith method is recommended as the sole method for determining ET[subscript o].