Climate Question Answers: NCERT Class 9 Social Science - Contemporary India

(i) (c) Mawsynram

(ii) (c) Loo

(iii) (b) Western disturbances

(v) (b) Early June

(v) (c) Cool days and cold nights

1. The elements which are affecting the climate are: temperature, atmospheric pressure, wind, humidity and precipitation.

2. India comes in the inter tropical convergence zone (ITCZ) also with several other factors like the EI nino, jet stream and coriolois force are the main reasons for monsoon type of climate in India.

3. Northwestern part of india experiences the highest diurnal temperature range. This happens because of the presence of thar desert and also because this region doesn't contain the moderating influence of the ocean.

4. Malabar coast gets rains from depressions and cyclones.

5. Jet streams are high velocity westerly winds that are blowing through a narrow zone in the upper troposphere layer. The westerly flows are responsible for the western disturbances that is experienced in the north western parts of the country. The easterly jet streams cause the tropical depressions during the monsoon as well as October-november months.

6. Monsoon refers to the seasonal wind direction reversal. Monsoon break refers to the happening of wet and dry spells during the rainy season. The monsoon rains take place only for a few days at a particular time.

7. Although there are wide variations in weather patterns across India, the monsoon bring some unifying influence on India. The Indian landscape, its flora and fauna etc. are highly influenced by the monsoon. Most of the festivals in India are related to agricultural cycle.

The Bay of Bengal is the branch of monsoon winds that moves towards northeast and return westwards covering the northern plain region. While they move towards west, their moisture contains tends to reduce with subsequent rains. Hence, the rainfall decreases in amount from east to west in northern India.

(i) Seasonal wind direction reversal over the Indian subcontinent takes place due to the pressure differential. El Nino has major role to play in the seasonal wind direction reversal over the Indian subcontinent.

(ii) The monsoon begins from the June's first week and advances quite rapidly to cover almost the whole country by mid-July. Hence, the bulk of rainfall in India is concentrated over the months; mainly June to August.

(iii) The Tamil Nadu coast receives winter rainfall because of movement of low-pressure conditions to the Bay of Bengal.

(iv) The Bay of Bengal is the centre of several pressure changes and hence there is always a chance of development of cyclone. Due to this, the delta region of the eastern coast is frequently struck by cyclones.

(v) The parts fall in the rain shadow area of the Aravalli. Hence, they are drought prone areas.

Indian Peninsular region shows wide variations in the climatic conditions across several regions. For example; during the winter season, temperature goes into negative in the Himalayan region. In the northwestern India, temperatures can range between 0º to 15°C during the winters. During the same season, the temperature in Chennai remains 25°C. The same variation can be seen in summers as well, while the temperature in Rajasthan can be around 47°C, it is a comfortable 30°C in Chennai.

Following are the factors responsible for the mechanism of monsoon:

(i) Sun causes the differential heating and cooling of land and water. This creates low pressure on India's landmass and high pressure over the oceanic surface. 

(ii) The inter tropical convergence zone (ITCZ) is normally positioned approx 5 N of the equator. It shifts over the ganga plains during the summers which is also called as the monsoon trough during the season of monsoon.

(iii) The high pressure area, east of Madagascar is about 20 S over the indian ocean which affects the Indian monsoon.

(iv) The Tibetan plateau gets intensely heated during the summers which results in strong vertical air currents and formation of high pressure over the plateau. This high pressure zone is approx. 9 km above the sea level . The westerly jet stream moves to the north of the himalayas and the tropical easterly jet stream moves over the Indian peninsula during the summers.

The temperature ranges between 10°-15°C in the northern plains region. The weather is most marked by seeing the clear sky, low temperatures, low humidity and weak variable winds. The inflow of the cyclonic confusion from the west and the northwest is a deterministic feature of the cold weather over the northern plain regions. These low-pressure systems originate over the Mediterranean Sea and Western Asia and then move into India. They cause winter rains over the plains and snowfall in the mountaineous region.

Characteristics of the monsoon rainfall in India: the duration of the monsoon varies from approximately 100 to 120 days from early june to mid September. The monsoon arrives at the southern tip of the Indian peninsular region generally by the june's first week. They are distinguished from the pre-monsoon showers because of their increase in amount of rainfall and regularity.

Effects of the monsoon rainfall in india: Agriculture in India largely depends on monsoons for water. Late, low or excessive rains have negative impact upon the crops. Due to the uneven distribution of rainfall across the country there are few places that are drought prone affected and few are flood affected. The monsoon provides India with a diverse climatic pattern. Hence, in spite of the presence of great regional variations, it has a unflying influence upon the country and people of this region.