Concept of Temperature in Atmosphere
•It is the measurement of available heat energy in a system.
•The atmosphere is not heated directly by insolation or the Sun’s rays; rather it is heated from below by the warmed surface of the earth, i.e. from terrestrial radiation.
•The lower levels of the atmosphere are heated by conduction.
•The earth’s surface is heated during day time after receiving solar radiation.
•The upper levels of the earth get heated by convection.
•The air coming in contact with the warmer surface of the earth gets heated and expands in volume.
•The warmer air rose up and forms vertical circulation of air.
•This mechanism transports heat from the ground surface to the atmosphere, thus helps in heating up of the atmosphere.
Determinants of Temperature:
•The average temperature of the earth is about 15’C.
•The spatial distribution of temperature is determined by the following factors-
•In general, average temperature decreases form the equator towards the poles because the sun rays become more and more oblique poleward.
•Consequently, the lower latitudes record high temperature as compared to the higher latitudes.
•The temperature decreases with increasing height from the earth’s surface at an average rate of 6.5 °C per 1000 m.
•The lower layer of air contains more vapour hence it absorbs more heat radiated from the earth’s surface than the upper air layers.
•There is a direct effect of cloud cover on the amount of insolation.
•Clouds have the effect of reducing the amount both of insolation, which reaches the surface of the earth and of outgoing radiation from the earth’s surface.
•As a result, tropical rain forests with dense cloud cover have very little range of temperature, where as, the hot deserts, which havecomparatively less cloud cover, have both high diurnal and annual temperature ranges.
Distance from the Sea/Ocean:
•The location of a place in relation to sea and or oceans also affects the distribution of temperature.
•In general, the sea has a moderating effect on the temperatures of the coastal areas throughout the year.
•On the other hand, regions deep within the interior of land masses experience extreme temperatures. This phenomenon is known as continentality.
•The winds help in the redistribution of temperature and in carrying moderating effects of the oceans to the adjacent coastal areas.
•For example, the wind blowing from low latitudes to high latitudes raise the temperature of the region, while winds blowing from high latitudes to low latitudes lower the temperature.
Topography and slope:
•The ground slope facing the Sun receives more insolation(temperature) than the leeward slopes.
•For example, the sothern slopes of Himalayas record more temperature than that of the northern slopes.
•The ocean currents also affect the distribution of temperature on the land and oceans.
•The warm ocean currents flowing from the lower latitudes to the higher latitudes carry warm water towards the polar areas,while the cold water currents bring the cold water towards the equatorial regions.
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