Give a geographical reason for each of the following:

(i) The total volume of water in the oceans and seas remains constant.

(ii) In Equatorial regions the sky often remains overcast with clouds.

(iii) When relative humidity is 100% the temperature reading on both wet and dry thermometers is the same.

(i) The total volume of water in the oceans and seas remains constant because all the water that evaporates from the earth's water bodies is eventually returned to it directly by the process of condensation and precipitation, and indirectly by stream and overflow from land surfaces.

(ii) In Equatorial regions the sky often remains overcast with clouds due to excessive heat. The high temperature leads to the rapid heating of air. Such heated air rises in convectional currents, leading to development of clouds at about 10 km height.

(iii) This is because when relative humidity is 100%, the air is fully saturated with moisture and it will not hold any more vapour at that temperature. Since saturated air will not allow evaporation, the temperature reading on both the dry and wet thermometers will be the same.