why is relative humidity high in the equatorial regions and minimum in the tropical deserts
Answers
Because of the height of the sun above the horizon (the solar elevation angle is always very roughly close to 90 degrees, give or take roughly around 23 degrees or so if you are close to the equator), the sun’s rays do not have to shine through a lot of air to get to the ground. Also the energy falling on 1 square metre of horizontal surface is high, because solar elevation angles are large. Its like shining a torch directly at a surface rather than shining so that there is a small angle between ground and direction of torch beam. As to the humidity, most of the rain in the tropics is convectional rain and with rain falling you have a lot of evaporation after rains. Actually it is not all that humid in some parts of the tropics, but if you are close to the sea the air will hold a lot of moisture. Where there is a lot of rain in the tropics a lot of solar energy is used up in evaporation and temperatures are usually not higher than 35 deg C or so. For heat, deserts near the equator can have temperatures well over 40 deg C. The relative humidity in Antarctica is often over 80%, so relative humidity there is often higher than relative humidity in the equatorial regions, but the air is so cold it holds far less water vapour per cubic metre than hot dry deserts do.
Answer:
subtropical areas tend to have less cloud cover than equatorial areas