1. Why are Polar easterlies called so?
The polar winds are the cold winds that blow from the high pressure areas towards the sub polar low pressure belts. These winds blow from the east in both the hemispheres due to the Coriolis force. Hence these are known as Polar easterlies.
2. When temperature increases atmospheric pressure decreases, when temperature decreases atmospheric pressure increases. Why?
Like any other matter, air also expands when it gets heated. The expanded air is less dense and hence it ascends. This leads to the lowering of atmospheric pressure. The ascending air spreads to the sides and cools. On cooling, it becomes dense and descends. As a result the atmospheric pressure increases.
3. Which are the major local winds that are blown in India.
$ Loo
$ Mangoshowers
$ Kalbaisakhi
4. Monsoon doesn’t occur in the Northern European region. Why?
The formation of the Monsoon winds happens only when the sun’s rays fall vertically from equator to Tropic of Cancer and to Tropic of Capricorn. Another important factor is the unproportional heating and cooling of the land and the sea. The North European zone locates near the Arctic zone. Therefore the availability of sun’s heat is very low. Because of this, monsoon does not occur in this area.
5. Why did monsoon winds cause trouble to Gama on his return to Malindi?
The south west monsoon gave a great help to Vasco da Gama in his arrival to India. His voyage was mainly depended on the favourable direction of the monsoon winds. But Gama tried to utilise the same wind for his return voyage to Portugal. But the direction of the south west monsoon was quite against his route. So his voyage to Malindi became too difficult.
6. How do friction affect the speed of wind?
The speed of wind will be high over ocean surfaces and level lands as the friction is less. On the other hand, as the friction being more along difficult terrains and places with dense forest cover, the speed of wind will be less in those places.
7. Given below are some of the chara- cteristics of Global winds. Identify each of them are related to which Global winds.
The polar winds are the cold winds that blow from the high pressure areas towards the sub polar low pressure belts. These winds blow from the east in both the hemispheres due to the Coriolis force. Hence these are known as Polar easterlies.
2. When temperature increases atmospheric pressure decreases, when temperature decreases atmospheric pressure increases. Why?
Like any other matter, air also expands when it gets heated. The expanded air is less dense and hence it ascends. This leads to the lowering of atmospheric pressure. The ascending air spreads to the sides and cools. On cooling, it becomes dense and descends. As a result the atmospheric pressure increases.
3. Which are the major local winds that are blown in India.
$ Loo
$ Mangoshowers
$ Kalbaisakhi
4. Monsoon doesn’t occur in the Northern European region. Why?
The formation of the Monsoon winds happens only when the sun’s rays fall vertically from equator to Tropic of Cancer and to Tropic of Capricorn. Another important factor is the unproportional heating and cooling of the land and the sea. The North European zone locates near the Arctic zone. Therefore the availability of sun’s heat is very low. Because of this, monsoon does not occur in this area.
5. Why did monsoon winds cause trouble to Gama on his return to Malindi?
The south west monsoon gave a great help to Vasco da Gama in his arrival to India. His voyage was mainly depended on the favourable direction of the monsoon winds. But Gama tried to utilise the same wind for his return voyage to Portugal. But the direction of the south west monsoon was quite against his route. So his voyage to Malindi became too difficult.
6. How do friction affect the speed of wind?
The speed of wind will be high over ocean surfaces and level lands as the friction is less. On the other hand, as the friction being more along difficult terrains and places with dense forest cover, the speed of wind will be less in those places.
7. Given below are some of the chara- cteristics of Global winds. Identify each of them are related to which Global winds.
Answer: a. Westerlies
b. Polar winds c. Trade winds
8. How does the altitude, temperature and humidity influences atmospheric pressure?
Altitude : The atmospheric pressure decreases with altitude. The pressure decreases at the rate of 1 millibar (mb) per an altitude of 10 meters. The ratification of air with altitude is the reason for this decrease in atmospheric pressure. The ratification of air with altitude is the reason for this decrease in atmospheric pressure. The atmospheric pressure and the altitude are inversely proportional.
Temperature : Air expands when it gets heated. The expanded air is less dense and hence it ascends. This leads to the lowering of atmospheric pressure. The ascending air spreads to the sides and cools. On cooling, it becomes dense and descends. As a result the atmospheric pressure increases.
Humidity : Humidity refers to the quantity of water present in the atmosphere. Water vapour is lighter than air and hence it ascends. If the quantity of water vapour is more in a unit volume of air, then naturally the atmospheric pressure will be less. Humidity and atmospheric pressure are inversely proportional.
9. Which local wind is known as ‘Snow-eater’. Why is it called so?
Chinook is a local wind that blows down the eastern slope of the Rockie mountains in North America. As a result of these winds, the snow along the eastern slopes of the Rockies melts, away. The term Chinook means ‘snow eater’ a term that suits to its peculiarity.
10. The speed of wind will be high over ocean surfaces and level lands. Why?
The speed of wind will be high over ocean surfaces and level lands as the friction is less. On the other hand, the friction being more along difficult terrains, the speed of wind will be less.
11. Arrange the items in B and C columns suitable to column A.
12. Which wind is known as Roaring Forties from the following.
(a. Polar Easterlies. b. Westerlies.
C. Monsoon winds. d. Trade winds)
Ans: Westerlies
13. (i) Name the smooth lines in the diagram.
(ii) Among the places A and B, identify the place experiencing high pressure and the place experiencing low pressure.
(iii) The sun is in which hemisphere during the period?
Answer: i. Isobars
ii. A- Low pressure, B- High pressure.
iii. Sun is in Northern hemisphere.
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