A. Fill in the blanks with appropriate words.
- The equatorial low pressure belt is also called the doldrums.
- Planetary winds are also known as permanent winds.
- Land breeze is a local wind.
- The Loo is the local wind that blows in Rajasthan.
- The Chinook wind is also known as the ‘snow eater.’
B. Match the rows.
| Column 1 | Column 2 |
| 1. Land breeze | (a) Local wind |
| 2. Loo | (b) Equatorial Low-pressure belt |
| 3. Doldrums | (c) Trade Winds |
| 4. High temperature | (d) Periodic wind |
| 5. Drying planetary winds | (e) Low-pressure |
| Column 1 | Column 2 |
| 1. Land breeze | (d) Periodic wind |
| 2. Loo | (a) Local wind |
| 3. Doldrums | (b) Equatorial Low-pressure belt |
| 4. High temperature | (e) Low-pressure |
| 5. Drying planetary winds | (c) Trade Winds |
C. Write true or false. Correct the false sentences.
- Temperature does not affect the atmospheric pressure at a place. — False
Correction: Temperature affects the atmospheric pressure at a place. - The unit for measuring atmospheric pressure is millibar. — True
- The area nicknamed ‘doldrums’ is the polar high-pressure belt. — False
Correction: The area nicknamed ‘doldrums’ is the equatorial low-pressure belt. - The direction from which the Westerlies blow in the northern hemisphere is north-west. — False
Correction: The Westerlies blow from the south-west in the northern hemisphere. - The loo blows in summers. — True
D. Choose the correct answer.
- The instrument used to measure air pressure is called the
(a) barometer (b) thermometer (c) hygrometer (d) wind vane
Answer: (a) barometer - The equatorial low-pressure belt is located
(a) between 5°N and 5°S latitudes
(b) around 30°N and S latitudes
(c) around 45°N and S latitudes
(d) around 60° latitudes
Answer: (a) between 5°N and 5°S latitudes - South Westerlies blow in the
(a) northern hemisphere
(b) southern hemisphere
(c) frigid zone of southern hemisphere
(d) frigid zone of northern hemisphere
Answer: (b) southern hemisphere - Chinook is a local wind that blows down the slopes of the
(a) Andes (b) Alps (c) Rockies (d) Urals
Answer: (c) Rockies - Assertion: The planetary winds are also called seasonal winds.
Reason: The unequal heating and cooling of land and water is the main cause of these winds.
(a) A is true, but (B) is false.
(b) (A) and (B) are both false.
(c) (A) is false, but (B) is true.
(d) (A) and (B) are both true.
Answer: (c) (A) is false, but (B) is true.
E. Answer the following questions in one or two sentences (60–70 words each).
- Define atmospheric pressure.
Atmospheric pressure is the weight or force that the air exerts on the Earth’s surface. It is measured using an instrument called a barometer and expressed in millibars. The pressure is highest at sea level and decreases with height because the density of air becomes lower as we move upward in the atmosphere.
- Name the factors that determine atmospheric pressure on earth.
The main factors that determine atmospheric pressure are temperature, altitude, and the amount of water vapour in the air. Warm air expands and creates low pressure, while cold air contracts and creates high pressure. Pressure also decreases with height, and humid air (air with water vapour) is lighter than dry air, affecting pressure levels.
- What is a wind?
Wind is the movement of air from areas of high pressure to areas of low pressure. The uneven heating of the Earth’s surface by the Sun creates pressure differences that cause air to move. Winds can be permanent, periodic, or local, depending on how regularly they occur and the regions in which they blow.
- What is the direction in which polar winds blow on the surface of the earth?
Polar winds blow from the high-pressure areas around the poles toward the low-pressure areas in the subpolar regions. In both hemispheres, they blow from the east, so they are also called easterlies. These winds are cold and dry because they come from the icy polar regions of the Earth.
F. Give reasons for the following (60–70 words each).
- Why does air create high pressure?
Air creates high pressure when it becomes cool and dense. Cold air molecules come closer together, making the air heavier. This heavy air sinks toward the surface of the Earth, exerting more force on it. As a result, the area experiences high atmospheric pressure. High-pressure regions usually have clear skies and dry weather.
- Why have tropical hot deserts come into existence?
Tropical hot deserts exist mainly because they lie under high-pressure belts near the Tropics of Cancer and Capricorn. In these regions, dry air descends from the upper atmosphere, preventing cloud formation and rainfall. This sinking dry air and constant sunlight make the regions extremely hot and arid, leading to the formation of deserts like the Sahara and Thar.
- Why do land and sea breezes occur?
Land and sea breezes occur due to the difference in heating and cooling rates of land and water. During the day, land heats up faster, creating low pressure, so cooler air from the sea moves toward the land (sea breeze). At night, the land cools faster, creating high pressure, so air moves from land to sea (land breeze).
G. Answer the following questions (60–70 words each).
- What is the equatorial low-pressure belt?
The equatorial low-pressure belt is a zone located roughly between 5°N and 5°S latitudes. It is also known as the doldrums. In this region, the Sun’s rays are most direct, making the air hot and light. The warm air rises continuously, creating a low-pressure area. This zone is usually calm with little or no wind movement.
- Differentiate between Trade Winds and Westerlies.
| S.NO | Trade Winds | Westerlies |
| 1. Direction of Flow | Trade Winds blow from east to west. | Westerlies blow from west to east. |
| 2. Location | They blow between 30° North and 30° South latitudes. | They blow between 30° and 60° latitudes in both hemispheres. |
| 3. Origin | They originate from the subtropical high-pressure belts and move toward the equatorial low-pressure belt. | They originate from the subtropical high-pressure belts and move toward the subpolar low-pressure belt. |
| 4. Nature | Trade Winds are steady, regular, and constant throughout the year. | Westerlies are less steady and stronger, often bringing rain. |
| 5. Effect | They help ships sail easily near the equator and influence tropical climates. | They bring rain to coastal areas and affect the weather of temperate regions. |
- Explain periodic winds with examples.
Periodic winds change their direction regularly due to temperature differences between land and water. They include monsoon winds, land breezes, and sea breezes. For example, in India, monsoon winds bring rain in summer and dry air in winter. These winds follow a definite pattern depending on the season or time of day.
- How are periodic winds different from permanent winds?
Periodic winds change their direction with time or season, while permanent winds blow in the same direction throughout the year. Permanent winds, like Trade Winds and Westerlies, are caused by the Earth’s rotation and pressure belts. Periodic winds, like monsoons and sea breezes, are caused by temperature differences between land and sea.
- What is a local wind? Write the characteristics of any one local wind.
Local winds blow only in a small region and for a short duration. They are caused by local temperature and pressure differences. For example, Loo is a hot and dry local wind that blows over northern India during summer. It raises temperatures sharply and often causes heat strokes due to its dryness and high speed.