(i) The sudden ascent of warm moist air on the windward sides causes cooling of air, leading to condensation and precipitation.
On the contrary, on descending the leeward slope, a decrease in altitude increases both the pressure and the temperature, leading the air to get compressed and warm. Consequently, the relative humidity drops and there is evaporation and little or no precipitation in the rain shadow area. Hence, a rain shadow area is generally dry.
(ii) Frontal rain is common in mid-latitudes due to the meeting of the sub-tropical and polar air masses. It is caused by convergence of two different air masses with different temperatures and other physical properties. When warm and cold air masses confront each other, the warmer air generally climbs above the colder air. The rising air is cooled while undergoing a frontal lift. This causes precipitation. Such precipitation is called cyclonic rainfall.
(iii) Convectional rainfall is called 4 o'clock rainfall as this type of rainfall occurs in the afternoon at about 4 o'clock. This is because the heat from the sun builds up throughout the day, causing the air to rise and form clouds that eventually bring rain in late afternoon around 4 o'clock.