# IAS Prelims Exam: Physical Geography NCERT Questions: ATMOSPHERIC CIRCULATION AND WEATHER SYSTEMS

Jagran Josh

For the Civil Services IAS Exam Geography has vast and it covers most sections of the General Studies for the IAS Prelims Exam. The geography is scientific in its orientation and hence the IAS Aspirants having Arts background find it very difficult to prepare the geography for the IAS Prelims Exam.

Q1. Consider the following statements
1. Wind moves from low pressure areas to high pressure areas.
2. Due to gravity the air at the surface is denser and hence has higher pressure.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Answer: b

Explanation:
Due to gravity the air at the surface is denser and hence has higher pressure. The pressure decreases with height. Wind always moves from high pressure areas to low pressure areas.

Q2. Consider the following statements regarding pressure gradient force
1. It produced by differences in atmospheric pressure
2.    Pressure gradient is strong where the isobars are apart.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Answer: a

Explanation:
The differences in atmospheric pressure produce a force. The rate of change of pressure with respect to distance is the pressure gradient. The pressure gradient is strong where the isobars are close to each other and is weak where the isobars are apart.

Q3. Consider the following statements regarding frictional force acting on wind
1. It is greatest in high altitudes.
2. Over the sea frictional force is minimum.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Answer: b

Explanation:
Frictional force affects the speed of the wind. It is greatest at the surface and its influence generally extends up to an elevation of 1 - 3 km. Over the sea surface the friction is minimal.

Q4. With reference to Coriolis force, which of the following is/are true?
1. In southern hemisphere it deflects the wind to the left.
2. Coriolis force is directly proportional to the velocity of wind.
3. The Coriolis force acts perpendicular to the pressure gradient force

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Answer: d

Explanation:
It deflects the wind to the right direction in the northern hemisphere and to the left in the southern hemisphere. The deflection is more when the wind velocity is high. The pressure gradient force is perpendicular to an isobar. The higher the pressure gradient force, the more is the velocity of the wind and the larger is the deflection in the direction of wind.

Q5. Consider the following statements
1. The wind circulation around a high is called cyclonic circulation.
2. Over high pressure area the air will subside from above and diverge at the surface.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Answer:

Explanation:
The wind circulation around a low is called cyclonic circulation. Around a high it is called anti cyclonic circulation. Generally, over low pressure area the air will converge and rise. Over high pressure area the air will subside from above and diverge at the surface.

Q6. Pattern of planetary winds depends on which of the following?
1. Distribution of continents and oceans
2. The rotation of earth
3. Migration of pressure belts following apparent path of the sun

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Answer: d

Explanation:
The pattern of planetary winds largely depends on (i) latitudinal variation of atmospheric heating(ii) emergence of pressure belts (iii) the migration of belts following apparent path of the sun(iv) the distribution of continents and oceans (v) the rotation of earth.

Q7. Consider the following statements
1. Oceanic water circulation is set in motion by general circulation of atmosphere.
2. Pattern of movement of planetary winds and local winds is called general circulation of atmosphere.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Answer: a

Explanation:
The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. The general circulation of the atmosphere also sets in motion the ocean water circulation which influences the earth’s climate.

Q8. With reference to Inter Tropical Convergence Zone (ITCZ), which of the following is/are true?
1. It is low pressure zone where winds from tropics converge.
2. It raises upto 14km in troposphere and reaches land surfaces near equator as Easterlies.
3.  It is zone of convergence of easterlies from either side of the equator.

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Answer: d

Explanation:
The air at the Inter Tropical Convergence Zone (ITCZ) rises because of convection caused by high insolation and a low pressure is created. The winds from the tropics converge at this low pressure zone. It reaches the top of the troposphere up to an altitude of 14 km. and moves towards the poles. This causes accumulation of air at about 30o N and S. Part of the accumulated air sinks to the ground and forms a subtropical high. Another reason for sinking is the cooling of air when it reaches 30o N and S latitudes. Down below near the land surface the air flows towards the equator as the easterlies. The easterlies from either side of the equator converge in the Inter Tropical Convergence Zone (ITCZ).

Q9. Katabatic wind is
a.    Cool air of high plateaus and ice fields
b.    Warm air of tropical desert
c.    Dry air on the leeward side of slope
d.    Cool air in the windward side of slope

Answer: a

Explanation:
During the night the slopes get cooled and the dense air descends into the valley as the mountain wind. The cool air, of the high plateaus and ice fields draining into the valley is called katabatic wind.

Q10. Consider the following statements
1. If the warm air mass moves towards the cold air mass, the contact zone is a cold front.
2. Occluded front is air mass fully lifted above land surface.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Answer: b

Explanation:
When the cold air moves towards the warm air mass, its contact zone is called the cold front, whereas if the warm air mass moves towards the cold air mass, the contact zone is a warm front. If an air mass is fully lifted above the land surface, it is called the occluded front.

Q11. Which of the following is/are about “Fronts”?
1. Fronts occur at equatorial regions.
2. They are characterised by steep gradient in temperature and pressure.
3.  They bring abrupt changes in temperature.

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Answer: c

Explanation:
When two different air masses meet, the boundary zone between them is called a front. The process of formation of the fronts is known as frontogenesis. The fronts occur in middle latitudes and are characterised by steep gradient in temperature and pressure. They bring abrupt changes in temperature and cause the air to rise to form clouds and cause precipitation.

Q12. Which of the following is/are true about tropical cyclones?
1. Clear frontal system is visible in tropical cyclones.
2.  Tropical cyclones originate over land and sea.
3.  Tropical cyclones is more destructive than extra tropical cyclones.

Select the correct answer from the following codes
a.    Only 3
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Answer: a

Explanation:
The tropical cyclones do not have a clear frontal system. The tropical cyclones
originate only over the seas and on reaching the land they dissipate. The wind velocity in a tropical cyclone is much higher and it is more destructive. Tropical cyclones, move from east to west.

Q13. Which of the following is/are true about Extra tropical cyclones?
1. They move from west to east.
2. Extra tropical cyclones affect large area compared to tropical cyclones.
3.  Extra tropical cyclones originate over land only.

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Answer: b

Explanation:
The extra tropical cyclones have a clear frontal system. They cover a larger area and can originate over the land and sea. The extra tropical cyclone affects a much larger area as compared to the tropical cyclone. The extra tropical cyclones move from west to east but tropical cyclones, move from east to west.

Q14. Which of the following is/are favourable conditions for the formation of tropical cyclones?
1.  Absence of the Coriolis force
2. Large sea surface with temperature higher than 27° C
3. Pre-existing weak low- pressure area

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Answer: c

Explanation:
Tropical cyclones originate and intensify over warm tropical oceans. The conditions favourable for the formation and intensification f tropical storms are (i) Large sea surface with temperature higher than 27° C (ii) Presence of the Coriolis force (iii) Small variations in the vertical wind speed (iv) A pre-existing weak low- pressure area or low-level-cyclonic circulation (v) Upper divergence above the sea level system.

Q15. Which of the following is/are true about thunder storms?
1. Thunderstorms are of short duration.
2. Thunderstorms occur over short area and are violent.
3. A thunderstorm is a well-grown cumulonimbus cloud producing thunder and lightning.

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Answer: d

Explanation:
Other severe local storms are thunderstorms and tornadoes. They are of short duration, occurring over a small area but are violent. Thunderstorms are caused by intense convection on moist hot days. A thunderstorm is a well-grown cumulonimbus cloud producing thunder and lightning.

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