Distribution of Temperature (Factors)

Factors Controlling the Distribution of Temperature

(i) Latitudes-

         The temperature of the atmos- phere of a particular place near the ground surface depends on the amount of insolation received at that place and the amount of insolation decreases from low latitudes towards high latitudes because the sun's rays become more and more oblique poleward and hence air temperature also decreases poleward.

(ii) Altitude-

      The temperature decreases with the increase in height from the earth's surface at an average rate of 6-5°C per kilometre due to follow radiation. ing two reasons:

(a) The major source of atmospheric heat is the earth's surface from where heat is transferred to the atmosphere through the processes of con- duction, radiation and convection. Thus the lower portion gets more heated than the above lying ones.

(b) The layers of air are denser near the earth's surface and become lighter with increasing altitudes. The lower layer of air contains more water vapour and dust particles than the layers above and hence it absorbs larger amount of heat radiated from the earth's surface than the upper air layers,

(iii) Distance from the Coast-

        The marine environment moderates the weather conditions to the coastal areas due to daily rhythems of land and sea breezes. Thus daily range of temperature near the coastal environment is minimum but it increases as the distance from the sea coast increases.

(iv) Nature of Land and Water-

           Land becomes warm and cold more quickly than the water body. So if equal amount of insolation is received the temperature of land becomes more than the temperature of the water body. It is due to the fact that Sun's rays penetrate more in the water than in the land which is opaque. But in case of water since it is transparent if has to warm more

Also a large amount of heat is lost in evaporation in case of seas and ocean. But in case of land very less amount of heat is lost in the name of evaporation. Also the specific heat (i.e., the amount of heat needed to raise the temperature of one gram of a substance by 1°C) of water is much greater than the land because the relative density of water is much lower than the land surface. Reflection from sea surface is also more than the land surface and thus water receives less insolation than the land.

(v) Nature of Ground Surface-

          The snow covered surfaces receive very low amount of inso lation because they reflect 70-90% of incoming short wave solar radiations and thus polar and arctic areas are characterised by extremely low temperature throughout the year. On the other hand sandy surfaces record high temperature during the day time in tropical and subtropical areas because they absorb most of the solar radiations and reflect only 20-30% of Solar

(vi) Nature of Ground Slope-

         The ground slope facing the Sun receives more insolation because the Sun's rays reach the surface more or less straight and hence sun facing ground surfaces record higher temperature than the leeward slopes where sun's rays reach more obliquely. In the northern hemisphere the southward facing slopes of east-west stretching mountains receive greater amount of insolation than the northward facing slopes because of their exposure to the sun for longer duration

(vii) Prevailing Wind-

              The winds blowing from the low latitudes to the high latitudes raise the temperature of the regions where they blow while winds blowing from high latitudes to low latitudes lower the temperature. Also the wind blowing from oceans to coastal areas bring in marine effects and lower the daily range of temperature. The winds coming from higher parts of the mountains lower the temperature in the valleys.

(viii) Ocean Currents-

              The warm ocean currents flowing from tropical areas to temperate and cold zones raise the average temperature in the affected areas. For example : Gulf stream raises the average temperature of the coastal areas of north western Europe.