(a) Explain four reasons for which temperature decreases with height within the troposphere.
(b) With the aid of a diagram, describe the mode of formation of orographic rainfall.
(a) Reasons for which Temperature Decreases with Height Within the Troposphere: -Air is not heated directly by the sun's rays -Rays strike the earth's surface and heat it first -Air receives its heat from the heat absorbed by the earth's surface -Through the processes of conduction and convection-Since the earth surface is heated first, places closer to the earth experience high temperature -Temperature decreases with height -The rate of decrease is known as environmental lapse rate -Which is 6.5°C for every 1000m of ascent -When unsaturated air mass ascends vertically, it expands and cools adiabatically -Air receives heat from CO,, S0, and aerosols which are more concentrated near the surface - Air density is more at the base and as such holds more heat than the scanty air molecules at higher altitude.
(b)
Description of the Mode of Formation of Orographic Rainfall:--Also called relief rainfall -Air absorbs water as it flows over land and water bodies -Relief rainfall develops in highland areas -Air comes into contact with a barrier such as mountain-Air is forced to rise or ascend -As it rises, it is Cooled by expansion in the higher altitudes due to decrease in atmospheric pressure -Further ascent cools the air until it is saturated at dew point-Condensation takes place-Clouds are formed -Further cooling of the 'clouds leads to rain formation-Rain falls on the windward slope as relief rainfall -Dry descending wind at the leeward slope brings little or no rainfall.
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