[Geography] Factors responsible for the Change in Weather and Climate

The condition of the atmosphere at a particular time and place is called weather. the weather conditions are almost similar over a period of a few months, we call it a season. The weather conditions prevalent in different seasons during the course of a year are called the climate of that place. The climate varies from place to place.

The change in climate is due to the following factors :

1. Distance from the equator :

The amount of heat received from the sun at a place on the surface of the Earth depends upon its latitude or its distance from the Equator. There is a gradual fall in temperature as we move away from the Equator towards the poles. See- the following figure, We can notice that the rays of the sun are falling directly or vertically on the Equator. Thus they spread over a small area. Near the Poles, the rays of the sun are slanting and spread over a large area. This makes the area near the Equator hot and the area near the Poles cold. On the basis of heat received, we can divide the Earth into three zones. 23'/2°S

1. The area lying between the Tropic of Cancer and the Tropic of Capricorn on both sides of the Equator receives the direct rays of the sun and thus is very hot. This is called the Torrid Zone.

2. The area lying between the Arctic Circle and the North Pole and between the Antarctic Circle and the South Pole is far away from the Equator. It receives very slanting rays of the sun and is therefore very cold. This is called the Frigid Zone.

3. The area lying between the Torrid Zone and the Frigid Zone is neither very hot nor very cold. This is called the Temperate Zone. Thus we can say that places located near the Equator have hot climate, and those located far away have cooler climate. Thus the latitude or the distance of a place from the Equator affects its climate.

2. Height above the seal level :

The temperature decreases with increase in height above the sea level. Some places like Ooty in South India are cooler than others though they are at the same distance from the Equator. This is due to height above sea level. For example, the temperature at Shimla, both in winter and summer is much lower than at Ludhiana in Punjab, though they are almost at the same distance from the Equator. This is due to the location of Shimla at about 2150 metres above sea level, whereas Ludhiana is only 250 metres above sea level.

3. Distance from the sea :

Places near the sea coast have less difference between the temperature of summer and winter seasons in comparison to the temperature of those places which are located far away from the sea. For example, Mumbai is cooler than Delhi in summer and warmer in winter. We can experience the same difference between Kolkata and Lucknow. The air over the land surface is influenced by that over the sea. The amount of influence depends upon the distance from the sea. The places near the big water bodies have neither hot summer nor cold winter and thus have a moderate climate, while those which are far away from the sea generally have extremes of climate, that is hot summers and cold winters.

During the day, land gets heated faster than water. The warm air from the land flows towards the sea and cool air from the sea replaces the land. At night, the sea becomes warm and the land becomes cool. The warm air from the sea replaces the cool air of the land.

4. Direction of the winds :

The winds coming from hot areas bring high temperature, while those conning from cold areas bring low temperature. The winds coming from sea or oceans bring clouds and cause rains.

5. Humidity and rains :

The amount of moisture present in the air also affects the climate of a place. It is called humidity. Humidity in the air at a place depends upon its location and winds. The places near the sea are more humid than those in the interior and far away from the sea. The winds blowing from sea to land bring a lot of moisture with them and cool the air on the land. The amount of rainfall from these winds and its distribution have a great influence on climate. The dry places have either very hot or very cold climate while rainfall has a moderating effect on the climate of that place.

6. Ocean currents :

There are warm and cold currents in the seas and oceans. They mostly affect the climate in the coastal areas. When Western Europe is experiencing freezing temperatures, warm waters of the Gulf Stream bring a lot of relief to the people. The cool currents reduce the temperature in the Torrid Zone.

Remember :

1. The condition of air at a particular time and place is weather.

2. Climate varies from place to place.

3. The climate of a place depends upon—distance from the Equator, height above the sea level, distance from the sea, direction of winds, humidity in the air and ocean currents