Evaporation is the process by which water is transformed from liquid to gaseous form. Factors affecting the rate of evaporation are as under:
(i) Accessibility of water bodies: The rate of evaporation is higher over the oceans than on the continents.
(ii) Temperature: When the temperature of an air is high it is capable of holding more moisture in its body than a low temperature. It is because of this that the rate of evaporation is more in summers than in winters.
(iii) Air moisture: If the relative humidity of a sample of air is high it is capable of holding less moisture. On the other hand if the relative humidity is less, it can take more moisture. Hence, the rate of evaporation will be high. Aridity of the air also increases the rate of evaporation.
(iv) Wind: Wind also affects the rate of evaporation. If there is no wind the air which overlies a water surface will get saturated through evaporation. If there is wind it will blow that saturated or nearly saturated air away from the evaporating surface and replace it with air of lower humidity. This allows evaporation to continue as long as the wind keeps blowing saturated air away and brings drier air.
(v) Cloud cover: The cloud cover prevents solar radiation and thus influences the air temperature at a place. This way, it indirectly controls the process of evaporation.