Question 1

Which condition is least favourable for the development of a tropical cyclone?

Accepted Answer

Very weak Coriolis force very close to the equator Tropical cyclones need warm ocean water, abundant moisture, rising air, and usually weak vertical wind shear. They also require enough Coriolis force to turn converging winds and maintain organised rotation. The Coriolis parameter is nearly zero at the equator, so air cannot acquire the necessary spin there; this is why tropical cyclones rarely form within about five degrees of the equator. Warm water, moisture, and low wind shear are favourable, making option A the least favourable condition.

Question 2

Why does a tropical cyclone weaken quickly after reaching land?

Accepted Answer

Its supply of moisture and heat from the ocean is cut off A tropical cyclone is powered mainly by evaporation from a warm ocean and the release of latent heat when moist air rises and condenses. After landfall, the storm is cut off from this warm, moist energy source. Rough land surfaces also increase friction, disrupt the circulation, and promote weakening; mountains may further break the vortex. The Coriolis force does not suddenly vanish, and land pressure is not zero. Therefore, option A gives the main reason.

Question 3

The movement of mid-latitude cyclones is generally influenced by which wind belt?

Accepted Answer

The westerly wind belt Mid-latitude cyclones usually develop and travel in the westerly wind belt, where the prevailing winds generally blow from west to east. The upper-level westerlies, including the jet stream, can steer and accelerate these systems, although their exact paths may curve and vary. Trade winds dominate the tropics, polar easterlies occur nearer the poles, and a land breeze is a local coastal circulation. Hence option A is correct.

Question 4

Which air mass is most likely to be associated with Indian monsoonal rainfall?

Accepted Answer

Maritime tropical humid air mass During the summer monsoon, winds reaching India travel over warm tropical seas and acquire large amounts of water vapour. They are therefore maritime tropical air masses: warm, moist, and capable of producing widespread convection and rainfall when lifted over the land and mountains. Continental polar or Arctic air is generally cold and dry and cannot explain the main moisture supply of the Indian monsoon. Thus option A is the best answer.

Question 5

Why is upper-air divergence useful in an intense cyclone?

Accepted Answer

It removes rising air and helps maintain low pressure In a developing or intense cyclone, air converges near the surface and rises. Divergence at upper levels removes this rising air from above the storm centre, preventing excessive mass accumulation in the column. This supports continued ascent and helps maintain or deepen the surface low pressure. Upper divergence does not stop surface convergence; rather, the two flows are dynamically connected and help sustain the cyclone’s circulation and cloud-producing uplift.

Question 6

Why can strong vertical wind shear weaken a tropical cyclone?

Accepted Answer

It displaces the warm core and convective clouds Vertical wind shear means that wind speed or direction changes substantially with height. A tropical cyclone depends on a vertically aligned warm core and organized thunderstorms around its circulation centre. Strong shear tilts the vortex, separates the low-level centre from upper-level convection, and exposes the circulation to drier or less favourable air. As a result, heat and moisture are transported away from the core, reducing the storm’s ability to intensify.

Question 7

What happens to the warm sector when an occluded front forms?

Accepted Answer

Warm air is lifted away from the surface An occluded front develops when a faster-moving cold front catches a warm front. The warm air between them, called the warm sector, is lifted above the colder air masses rather than remaining at the surface. This removes the warm sector from direct contact with the ground and changes the cyclone’s frontal structure. Occlusion may still produce clouds and precipitation, but the surface warm sector becomes narrowed or disappears as it is lifted aloft.

Question 8

Under which condition can frontal precipitation continue for a long duration?

Accepted Answer

In a stationary frontal zone Frontal precipitation can continue for a long time when the front remains stationary or moves very slowly. At a stationary front, warm and cold air masses stay in contact, and one air mass is gradually lifted over the other. The rising air cools, condenses, forms clouds, and produces prolonged rain or snow. A dry anticyclone and a uniform air mass generally suppress such uplift and precipitation.

Question 9

Where is the most intense weather found around the eye of a tropical cyclone?

Accepted Answer

In the eyewall The eyewall is the ring of towering thunderstorms immediately surrounding the eye of a tropical cyclone. It contains the strongest upward convection, heaviest rainfall, and usually the highest sustained winds because the pressure gradient is very steep there. In contrast, the eye is often comparatively calm and may even have breaks in the cloud cover.

Question 10

What role can jet streams play in a frontal zone with strong temperature contrast?

Accepted Answer

They can create upper-level divergence and support cyclonic development Jet streams can influence the development of frontal cyclones through their pattern of winds aloft. In a favourable region, upper-level divergence removes air from above a surface low-pressure centre. This encourages air to rise, lowers surface pressure, and strengthens the cyclone. The effect depends on the jet configuration; it does not automatically turn every front into a tropical cyclone.

Question 11

A dry line may be considered an example of what type of boundary?

Accepted Answer

Boundary between air masses with similar temperature but different humidity A dry line is a sharp boundary separating a warm, moist air mass from a warmer or relatively dry air mass. Its defining contrast is moisture rather than a major temperature difference. Convergence along the line can force moist air upward and may trigger thunderstorms when instability is present. Therefore, it is an air-mass boundary based chiefly on humidity contrast.

Question 12

Supercooled droplets and freezing rain are more likely under which frontal condition?

Accepted Answer

At a warm front when cold air is trapped near the surface At a warm front, relatively warm air rises gradually over a shallow, colder surface air mass. Precipitation may melt while falling through a warm layer aloft and then encounter sub-freezing air near the ground. Raindrops can remain liquid below 0°C as supercooled drops and freeze on contact with surfaces, producing freezing rain. This layered structure makes option A correct.

Question 13

How can the Bergeron process enhance precipitation in frontal clouds?

Accepted Answer

Ice crystals grow faster than liquid water droplets The Bergeron process operates in clouds containing both ice crystals and supercooled liquid droplets. Because the saturation vapour pressure is lower over ice than over liquid water, water vapour moves toward the ice crystals. The crystals grow, become snowflakes or ice particles, and may melt while falling through warmer air to produce precipitation. Thus ice crystals grow more efficiently than liquid droplets.

Question 14

How does upper-atmospheric divergence help strengthen a surface cyclone?

Accepted Answer

It removes air aloft and can deepen the surface low-pressure centre A surface cyclone is associated with rising air and low pressure. If air diverges at high altitude, mass is removed from the atmospheric column above the surface low. Surface pressure can then fall further, encouraging additional low-level convergence and upward motion. This positive feedback may intensify the cyclone, especially when upper-air divergence is dynamically well placed. Hence option A is correct.

Question 15

Why is the rainfall belt in temperate cyclones often long and curved?

Accepted Answer

Because the front forms a long, curved boundary between air masses Temperate or mid-latitude cyclones develop along fronts, where contrasting warm and cold air masses meet. These frontal boundaries commonly extend over a considerable distance and curve around the cyclone’s low-pressure centre. Air is lifted along the fronts, producing cloud and precipitation in elongated bands rather than in a compact circular area. Thus the long, curved frontal boundary explains the rainfall belt, making option B correct.

Question 16

Why does contact between warm air and the surface decrease in an occluded front?

Accepted Answer

Because warm air is lifted above colder air masses An occluded front forms when a faster-moving cold front catches a warm front. The warm air in the cyclone’s warm sector is then forced upward, either over colder air ahead or over the colder air behind it. As a result, warm air is removed from direct contact with the ground, while clouds and precipitation may continue along the lifted air. Therefore, option A is correct.

Question 17

What can the formation of an eye in a tropical cyclone indicate?

Accepted Answer

An organized and intense cyclonic circulation The eye is the relatively calm central region of a mature tropical cyclone, surrounded by the eyewall where winds, convection, and rainfall are often strongest. A well-defined eye usually reflects a highly organized circulation and substantial intensity, although eye appearance can change during strengthening or weakening. It does not mean that the whole storm has weak clouds or that friction has disappeared. Hence option B is correct.

Question 18

Why may weather be prolonged but not very intense along a stationary front?

Accepted Answer

Because the front moves slowly, while uplift may be weak or persistent A stationary front separates contrasting air masses but has little net movement. Since the boundary remains near one region for a long time, clouds, drizzle, or intermittent rain may persist. However, the lifting may be gradual and stable rather than explosive, so the weather is not necessarily severe. Duration and intensity are different characteristics. Therefore, option B correctly explains the situation.

Question 19

Which step is central to fog formation when maritime tropical air moves over a cold surface?

Accepted Answer

Cooling of moist air until it approaches saturation When warm, moist maritime tropical air passes over a colder surface, it loses heat from below. The lower air cools toward its dew point, relative humidity rises, and condensation begins when saturation is reached. Tiny water droplets suspended near the ground then produce advection fog. Drying, pressure-gradient loss, and increased Coriolis force are not the essential steps. Thus option A is correct.

Question 20

Before a cyclonic wave forms on the polar front, which condition is considered necessary?

Accepted Answer

A distinct boundary between contrasting air masses The polar front is a zone where cold polar air meets warmer subtropical or tropical air. This strong contrast in temperature and density creates a baroclinic boundary that can become wavy under suitable upper-air and wind conditions. A developing wave may then deepen into a mid-latitude cyclone. Without contrasting air masses and a boundary between them, the basic polar-front mechanism would be absent. Hence option A is correct.

Question 21

What does increasing spacing between temperature lines mean in frontolysis?

Accepted Answer

The temperature gradient is weakening Frontolysis is the weakening or dissipation of a front. A front is strongest where contrasting air masses are separated by a sharp horizontal temperature gradient. If isotherms or temperature lines become more widely spaced, the temperature changes less over distance, so the thermal contrast and frontal intensity decrease. Hence option A correctly identifies the process.

Question 22

The nature of rainfall at a front mainly depends on what?

Accepted Answer

Frontal slope and rate of air uplift Rainfall along a front is produced when one air mass is forced to rise over another. The slope of the front controls how rapidly and over what horizontal distance the uplift occurs. A steep front usually produces stronger, narrower uplift and heavier showers, whereas a gently sloping front gives slower, broader uplift and more prolonged, lighter precipitation. Therefore, option A is correct.

Question 23

Which factor can accelerate the change of a small wave on the polar front into a deep low pressure?

Accepted Answer

Favourable combination of upper divergence and surface convergence Cyclogenesis occurs when a disturbance on the polar front intensifies into a low-pressure system. Divergence in the upper troposphere removes air from above the developing centre, reducing the mass of the air column and lowering surface pressure. Surface convergence supplies rising air into the system, while frontal temperature contrast supports development. Their favourable combination therefore accelerates deepening, making option A correct.

Question 24

Why is cyclonic rotation in the Southern Hemisphere different from that in the Northern Hemisphere?

Accepted Answer

The direction of Coriolis deflection reverses Cyclonic winds are curved by the Coriolis effect, which results from Earth’s rotation. The direction of this deflection is opposite in the two hemispheres: air is deflected to the left in the Southern Hemisphere and to the right in the Northern Hemisphere. Therefore, cyclone rotation differs between them.

Question 25

The presence of fronts in temperate cyclones is evidence of what?

Accepted Answer

A temperature and moisture contrast between different air masses A front is a boundary where two air masses with contrasting properties meet. In temperate cyclones, the contrasting air masses are commonly cold polar air and warmer tropical air, often with differences in humidity as well. Thus, fronts are evidence of strong air-mass contrast, not of a single uniform air mass.

Air masses, fronts, and cyclones

Practice questions

01 Which condition is least favourable for the development of a tropical cyclone?

02 Why does a tropical cyclone weaken quickly after reaching land?

03 The movement of mid-latitude cyclones is generally influenced by which wind belt?

04 Which air mass is most likely to be associated with Indian monsoonal rainfall?

05 Why is upper-air divergence useful in an intense cyclone?

06 Why can strong vertical wind shear weaken a tropical cyclone?

07 What happens to the warm sector when an occluded front forms?

08 Under which condition can frontal precipitation continue for a long duration?

09 Where is the most intense weather found around the eye of a tropical cyclone?

10 What role can jet streams play in a frontal zone with strong temperature contrast?

11 A dry line may be considered an example of what type of boundary?

12 Supercooled droplets and freezing rain are more likely under which frontal condition?

13 How can the Bergeron process enhance precipitation in frontal clouds?

14 How does upper-atmospheric divergence help strengthen a surface cyclone?

15 Why is the rainfall belt in temperate cyclones often long and curved?

16 Why does contact between warm air and the surface decrease in an occluded front?

17 What can the formation of an eye in a tropical cyclone indicate?

18 Why may weather be prolonged but not very intense along a stationary front?

19 Which step is central to fog formation when maritime tropical air moves over a cold surface?

20 Before a cyclonic wave forms on the polar front, which condition is considered necessary?

21 What does increasing spacing between temperature lines mean in frontolysis?

22 The nature of rainfall at a front mainly depends on what?

23 Which factor can accelerate the change of a small wave on the polar front into a deep low pressure?

24 Why is cyclonic rotation in the Southern Hemisphere different from that in the Northern Hemisphere?

25 The presence of fronts in temperate cyclones is evidence of what?

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