Latitudinal Variations

The latitudinal variation of temperature over the earth is the result of two main variables

• incoming solar radiation and
• the distribution of land and water masses

What do you think could be the other factors influencing temperature?

The movement of wind and water, and the direction of slopes of hills and mountains also modify the temperature.

We know that the length of the day varies at higher latitudes. That means the incoming solar radiation varies. However, if we compute the average, every point on the earth gets the same total hours of daylight each year, an average of 12 hours per day, but not the same amount of heat. The latter depends upbn the amount of radiant energy delivered/unit area/hr and this depends upon the angle of landing sunlight. You have learnt in the previous section that vertical beams afe more intense than the oblique beams that land on the higher latitudes. Hence we find a gradual decrease in the amount of incident radiant energytunit area along the increasing latitudes, horizontally.

On the basis of temperature variation three distinct heat zones can be distinguished in each hemisphere (Figure shown below). The hot torrid zones are near the equator. moderate or temperate zones are in the middle, the cold zones are at the poles. Each zone is characterised by typical plants and animal populations found in the area.