February 26, 2014

AP 10th Social New Text Book - Climate and Weather

Factors influencing climate and weather: It is observed for some places (e.g. Chennai) that there is not much difference in the temperature across months. Some places (e.g. Delhi) have wide differences in temperature across the months.

India experiences wide variations in temperature. The northern portion is bounded by the Himalayas whereas southern peninsula is surrounded by seas. Some places are far from the coasts; they are inland. Some places are at high altitude, whereas others are on the plain. The factors that affect climate are called climatic controls. These include:
1. Latitude
2. Land-water relationship
3. Relief
4. Upper air circulation

1. Latitude or distance from the equator

The average temperatures for the year drop the further an area is away from the equator. For this reason, we divide the regions on Earth as:
Tropical, those close to the Equator;
Polar, as those close to the poles;
Temperate, as those in between these two extremes.

If we compare the climate of, say, Indonesia and Japan, we can understand the differences. The reason for these differences is the differential heating of Earth that you have read in earlier classes. Intensity of temperature depends on the latitude. The temperature of the atmosphere at a particular place near the earth’s surface depends upon the insolation (heat from sun rays) received at that location. This is more intense in the low than in the high latitudes. As we move away from the equator towards the poles, the average annual temperature shows lower values.

Q. Using a globe recall and discuss what you may have read earlier. How does the angle of sun vary at different latitudes? What impact does this have?

In India the southern part lies in the tropical belt close to the equator. Owing to this, the region has higher average temperature than the northern part. This is one reason for the climate of Kanyakumari being entirely different from Bhopal or Delhi. India is situated roughly between 8o and 37o N latitudes and the country is divided in almost two equal parts by the Tropic of Cancer. The part south of the Tropic of Cancer lies in the tropical zone. The part north of the Tropic of Cancer lies in the temperate zone.

2. Land water relationship:

Look at map of India showing land cover and water bodies, and you will see another important factor which has an influence on climate: the land and water relationship . The amount of sunlight that is first absorbed and then radiated back or directly reflected depends on the nature of the surface. Darker areas, such as heavily vegetated regions, tend to be good absorbers; lighter areas, such as snow and ice - covered regions, tend to be good reflectors. The ocean absorbs and loses heat more slowly than land. This affects climate in many ways. One of this is the formation of land and sea breeze. From the illustration below explain how this happens.

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