discuss the factor affecting the non uniform distribution of temperature on the surface of the earth
Answers
The factors responsible for the uneven horizontal distribution of temperature are:
1. Latitude
In the previous article, we have studied that the angle of incidence of sun’s rays goes on decreasing from the equator towards the poles.
Higher the angle of incidence, higher is the temperature. Similarly, lower the angle of incidence, lower is the temperature.
This is why the temperature is higher near the tropical regions and decreases towards the poles.
2. Altitude
As we all know, the temperature in the troposphere goes on decreasing with increase in height.
Temperature decreases at an average rate of nearly 6 degree Celsius per 1000 m altitude, which is known as Normal Lapse Rate.
3. Land and Sea Contrast
Compared to land, the sea gets heated slowly and loses heat slowly. Land heats up and cools down quickly.
As a result, the temperature is relatively higher on land during day time and it is higher in water during the night.
Also, the places situated near the sea come under the moderating influence of the sea and land breezes which moderates the temperature.
There are also seasonal variations in the temperature of land and sea. During summer, the air above land has a higher temperature than the oceans. But the air above oceans gets higher temperature than landmass in winter.
Notwithstanding the great contrast between land and water surfaces, there are differences in the rate of heating of different land surfaces. A snow-covered land as in polar areas warms very slowly because of a large amount of reflection of solar energy. A vegetation covered land does not get excessively heated because a great amount of insolation is used in evaporating water from the plants.
4. Ocean Currents
Ocean Currents are of two types – warm and cold.
Warm currents make the coasts along which they flow warmer, while cold currents reduce the temperature of the coasts along which they flow.
The North-Western European Coasts do not freeze in winter due to the effect of North Atlantic Drift (a warm current), while the Quebec on the coast of Canada is frozen due to the Cold Labrador Current flowing along it, though the Quebec is situated in lower latitudes than the North-West European Coast.
5. Air Masses
Like the land and sea breezes, the passage of air masses also affects the temperature.
The places, which come under the influence of warm air masses experience higher temperature and the places that come under the influence of cold air masses experience low temperature.
6. Vegetation Cover
Soil devoid of vegetation cover receives heat more rapidly than the soil under vegetation cover. Because vegetation cover absorbs much of sun’s heat and then prevents quick radiation from the earth whereas the former radiates it more rapidly.
Hence the temperature variations in densely forested areas are lower than those in desert areas.
Note: Along with these, the other factors which are responsible for the uneven horizontal distribution of temperature are winds, nature of the soil, slope and aspect of the surface, relief features, etc.
The horizontal distribution of temperature over the globe can be studied easily from the isotherm maps of January and July months since the seasonal extremes of high and low temperature are most obvious in both northern and southern hemispheres during these months.