All questions of Climatology for UPSC CSE Exam

All statements are correct; hence answer is (d). There are six major controls of the climate of any place. They are latitude, altitude, pressure and wind system, distance from the sea (continentality), ocean currents and relief features.

Nitrogen as a Major Constituent of the Atmosphere

Nitrogen is one of the major constituents of the Earth's atmosphere, comprising about 79% of the atmospheric gases. It plays a crucial role in various biological processes and is an essential element for the survival and growth of living organisms.

1. Nitrogen as an Essential Constituent of Organic Compounds

Nitrogen is an essential component of organic compounds such as amino acids and proteins. Amino acids are the building blocks of proteins, which are vital for the structure and functioning of cells, tissues, and organs in all living organisms. Proteins have various functions in the body, including enzyme catalysis, cell signaling, transportation of molecules, and structural support.

The presence of nitrogen in organic compounds allows for the formation of peptide bonds between amino acids, leading to the synthesis of proteins. Without nitrogen, the synthesis of these essential biomolecules would not be possible, and life as we know it would not exist.

2. Nitrogen as a Principal Source of Free Nitrogen

The principal source of free nitrogen in the environment is the action of soil microorganisms and associated plant roots on atmospheric nitrogen. Nitrogen gas (N2) is abundant in the atmosphere, but most organisms cannot directly use it in this form. They require nitrogen in a more accessible form, such as ammonia (NH3) or nitrate (NO3-).

Certain nitrogen-fixing bacteria present in the soil, such as Rhizobium and Azotobacter, have the ability to convert atmospheric nitrogen into a usable form. These bacteria form symbiotic relationships with certain plants, such as legumes, where they colonize the roots and convert nitrogen gas into ammonia through a process called nitrogen fixation.

The ammonia produced by nitrogen-fixing bacteria can be further converted into nitrate by other soil bacteria in a process called nitrification. This nitrate can then be taken up by plants through their roots and utilized in the synthesis of organic compounds, such as amino acids and proteins. Thus, the action of soil microorganisms and associated plant roots is crucial in making atmospheric nitrogen available to living organisms.

Conclusion

Both statements provided in the question are correct. Nitrogen is indeed an essential constituent of organic compounds such as amino acids and proteins. Additionally, the principal source of free nitrogen is the action of soil microorganisms and associated plant roots on atmospheric nitrogen. Understanding the role of nitrogen in biological processes and its availability in the environment is important for studying various ecological and agricultural systems.

The concept of albedo refers to the ability of a surface to reflect sunlight back into space. The higher the albedo of a surface, the more sunlight it reflects, resulting in less absorption and less warming of the atmosphere. Conversely, a lower albedo means that a surface absorbs more sunlight, leading to more warming.

Lowest albedo: Moist ploughed soil

Moist ploughed soil is likely to have the lowest albedo among the given options. This is because soil is generally dark in color, which means that it absorbs more sunlight. Additionally, moist soil tends to be more reflective than dry soil, but still absorbs more sunlight than other materials like snow and clouds.

Other options and their albedo

- Thick cloud: Clouds have a high albedo, as they reflect a significant amount of sunlight back into space. Therefore, thick cloud is unlikely to have the lowest albedo.
- Fresh snow in Antarctica: Snow has a high albedo, as it reflects sunlight very effectively. Therefore, fresh snow in Antarctica is also unlikely to have the lowest albedo.
- Mirror: Mirrors have a very high albedo, as they reflect almost all of the sunlight that falls on them. Therefore, a mirror is also unlikely to have the lowest albedo.

Conclusion

In conclusion, moist ploughed soil is likely to have the lowest albedo among the given options. This means that it absorbs more sunlight, leading to more warming of the atmosphere. It is important to understand the concept of albedo in order to better understand the impact of different surfaces and materials on the Earth's climate.

Temperature inversion is most common in Mountain valleys.

Explanation:

Temperature inversion refers to a reversal of the normal atmospheric temperature gradient, where the temperature increases with altitude. In other words, instead of the temperature decreasing as we go higher in the atmosphere, it actually increases. This phenomenon is caused by the trapping of cool air near the surface of the Earth by a layer of warm air above it.

Inversions can occur in various locations, but they are most common in mountain valleys. Here's why:

1. Geographic Features:
- Mountain valleys are characterized by their topography, with high mountains surrounding a narrow valley floor.
- This topography plays a crucial role in the formation of temperature inversions.
- During the day, the sun heats up the valley floor, causing the air near the surface to warm and rise.
- However, at night, the valley floor cools rapidly due to radiative cooling, causing the air near the surface to become colder than the air above it.

2. Cold Air Drainage:
- In mountain valleys, cold air tends to drain down the slopes and accumulate in the valley bottom.
- This cold air becomes trapped beneath a layer of warmer air, leading to the formation of a temperature inversion.
- The surrounding mountains act as barriers, preventing the cold air from mixing with the warmer air above.

3. Stable Atmospheric Conditions:
- Temperature inversions are more likely to occur when the atmosphere is stable.
- In stable atmospheric conditions, there is little vertical mixing of air masses, allowing the inversion layer to persist.
- Mountain valleys often experience stable atmospheric conditions, especially during calm and clear nights when radiative cooling is most effective.

4. Local Climate:
- Mountain valleys tend to have specific climatic conditions that favor the formation of temperature inversions.
- The cool air trapped in the valley can lead to the accumulation of pollutants, such as smoke or fog, which further enhance the inversion layer.
- This can result in poor air quality and reduced visibility in these areas.

In conclusion, temperature inversions are most common in mountain valleys due to the geographic features, cold air drainage, stable atmospheric conditions, and local climate characteristics associated with these regions.

Explanation:

1. These are low-pressure regions:
Anticyclones are actually high-pressure systems, not low-pressure systems. In an anticyclone, the air is sinking and spreading outwards from a central region, creating higher pressure at the surface. This high-pressure system is characterized by clear skies, light winds, and dry weather conditions. So, statement 1 is incorrect.

2. Their extent is always small:
Anticyclones are typically smaller in size compared to other weather systems such as cyclones. They usually span a few hundred kilometers in diameter. Due to their smaller size, they have a more localized impact on weather patterns. So, statement 2 is correct.

3. Cloudy and precipitation conditions exist along with the cyclone:
This statement is incorrect. Anticyclones are associated with clear skies and dry weather conditions. The sinking air in an anticyclone inhibits the formation of clouds and precipitation. Instead, they are characterized by stable atmospheric conditions, which result in fair weather with minimal cloud cover and low chances of rainfall.

Conclusion:
Based on the explanations above, statement 1 is incorrect, statement 2 is correct, and statement 3 is incorrect. Therefore, the correct answer is option 'C' - only statement 2 is true.

Coriolis force is absent at the equator. Due to this, winds blowing from high-pressure sub-tropics to low-pressure tropics do not form a circulatory pattern around a low-pressure zone.

Zero Coriolis force at the equator:
- The Coriolis force is responsible for the deflection of winds in the Northern and Southern Hemispheres.
- At the equator, the Coriolis force is nearly zero due to the minimal effect of the Earth's rotation on the winds.

Presence of roaring forties:
- The roaring forties are strong westerly winds found in the Southern Hemisphere, generally between 40 and 50 degrees latitude.
- These winds are located much farther from the equator and do not directly impact the deflection of winds at the equator.

A large number of land breaks and bays:
- Landmasses and bodies of water, such as bays, can influence the direction and speed of winds.
- At the equator, there are a large number of land breaks and bays that can disrupt the flow of winds, leading to less deflection.

In conclusion, the winds are not deflected with great force at the equator primarily due to the zero Coriolis force at the equator. The presence of the roaring forties and a large number of land breaks and bays also play a role, but they are not as significant as the absence of the Coriolis force at the equator.

Explanation:

Absolute Humidity:
Absolute humidity refers to the actual amount of moisture present in the air, regardless of temperature. It is a measure of the total water vapor content in a given volume of air and is usually expressed in grams per cubic meter (g/m3) or grams per kilogram (g/kg).

Relative Humidity:
Relative humidity is the ratio of the actual amount of moisture present in the air to the maximum amount of moisture the air can hold at a particular temperature. It is expressed as a percentage and provides a measure of how close the air is to saturation. Relative humidity is dependent on both the temperature and the absolute humidity.

Specific Humidity:
Specific humidity is a measure of the actual amount of moisture present in the air on a mass basis. It is the ratio of the mass of water vapor to the total mass of the air parcel. Specific humidity is expressed in grams per kilogram (g/kg) and is not dependent on temperature.

Analysis of the Statements:
1. Absolute humidity is the water content of the air.
This statement is correct. Absolute humidity refers to the actual amount of moisture present in the air.

2. Relative humidity, expressed as a per cent, measures the current absolute humidity relative to the maximum for that temperature.
This statement is correct. Relative humidity is a measure of the current absolute humidity relative to the maximum amount of moisture the air can hold at a particular temperature.

3. Specific humidity is a ratio of the water vapor content of the mixture to the total air content on a mass basis.
This statement is incorrect. Specific humidity is a ratio of the water vapor content of the mixture to the total mass of the air parcel, not the total air content. It is not dependent on temperature.

Conclusion:
Based on the analysis, statement 3 is incorrect, while statements 1 and 2 are correct. Therefore, the correct answer is option 'D' - None of the above.

The correct answer is option 'C' - 1 and 2 only.

Explanation:
The Roaring Forties are strong westerly winds found in the Southern Hemisphere. These winds are primarily caused by two factors:

1. Air being displaced from the Equator towards the South Pole:
The Earth's rotation and the difference in temperature between the equator and the poles create a pressure gradient, causing air to flow from the equator towards the poles. This flow of air is known as the Ferrel cell. In the Southern Hemisphere, the air is deflected to the left due to the Coriolis effect, resulting in the westerly winds known as the Roaring Forties.

2. Earth's rotation:
The rotation of the Earth also plays a significant role in the formation of the Roaring Forties. The Coriolis effect, which is caused by the rotation of the Earth, causes the moving air to be deflected to the left in the Southern Hemisphere. This deflection is what creates the westerly winds.

However, the other options mentioned in the question are not directly responsible for the formation of the Roaring Forties:

3. Equatorial counter-currents:
Equatorial counter-currents refer to the eastward flowing currents found near the equator. While these currents do influence the ocean currents and atmospheric circulation patterns, they are not the main cause of the Roaring Forties.

4. Thermal dipole created in the Pacific Ocean:
A thermal dipole refers to the contrast in sea surface temperatures between two regions. While temperature differences can affect atmospheric circulation, a thermal dipole in the Pacific Ocean does not directly cause the Roaring Forties.

In conclusion, the Roaring Forties are primarily caused by the displacement of air from the Equator towards the South Pole and the Earth's rotation. Other factors such as equatorial counter-currents and thermal dipoles may influence the atmospheric circulation patterns but are not the primary causes of the Roaring Forties.

The general distribution of winds throughout the lower atmosphere is known as planetary winds. Confined within some latitudinal belts, these winds blow rather regularly throughout the year and are basically controlled by the latitudinal pressure belts.

The main planetary winds are (i) the North-east and the South-east Trade winds, (ii) the Temperate Westerlies and (iii) the Polar Easterlies, which blow from the polar high-pressure area to the temperate low-. Pressure area.

All of them are affected by Coriolis force (Earth's rotation on its axis), and migration of pressure belts apart from how heat patterns vary across the Earth (creating pressure difference).

Explanation:
The thermal equator is an imaginary circle around the Earth that connects the points where the highest mean annual temperature is recorded at each longitude. The following points explain why the thermal equator is slightly north of the geographical equator:

- Solar insolation is comparatively much higher in the Northern Hemisphere than in the Southern Hemisphere. This is due to the fact that the Earth's orbit is not circular but slightly elliptical. As a result, the Earth is closer to the Sun during the Northern Hemisphere summer than during the Southern Hemisphere summer. This means that there is more solar radiation falling on the Northern Hemisphere, leading to higher temperatures.

- The Northern Hemisphere is dominated by land, which heats up faster than water. Land has a lower heat capacity than water, which means that it takes less energy to raise its temperature. This is why temperatures in the interior of continents can be much higher than temperatures on the coasts. In contrast, the Southern Hemisphere is dominated by ocean waters, which have a higher heat capacity and take longer to warm up. This leads to lower temperatures in the Southern Hemisphere.

Therefore, both factors contribute to the fact that the thermal equator is slightly north of the geographical equator. Option B is the correct answer.

Rotation of earth on its axis gives rise to Coriolis force.

Introduction:
Sand and dust storms are natural phenomena that occur across the world. They have significant impacts on human health and the environment. This question focuses on three important aspects related to sand and dust storms.

Explanation:
1. They can travel thousands of kilometres across continents and oceans:
- Sand and dust storms are powerful atmospheric events that can transport vast amounts of sand and dust particles over long distances.
- These storms are often caused by strong winds that lift and carry particles from arid and desert regions.
- The particles can be carried over thousands of kilometers, crossing continents and even oceans.
- This phenomenon has been observed in various parts of the world, such as the Sahara desert dust reaching North America and the Asian dust storms reaching the Pacific Ocean.

2. Chronic exposure to fine dust contributes to premature deaths from respiratory and cardiovascular diseases:
- Fine dust particles, known as particulate matter (PM), are one of the major components of sand and dust storms.
- These particles are small enough to be inhaled deep into the respiratory system.
- Chronic exposure to PM can lead to various health problems, including respiratory and cardiovascular diseases.
- The fine particles can cause inflammation in the lungs, aggravate existing respiratory conditions, and increase the risk of heart attacks and strokes.
- Studies have shown a strong association between exposure to PM and premature deaths.

3. Deforestation, unsustainable agricultural practices, excessive water extraction, and modification of water bodies for irrigation and other purposes:
- These human activities have a direct impact on the occurrence and intensity of sand and dust storms.
- Deforestation reduces vegetation cover, which can lead to soil erosion and the formation of dust sources.
- Unsustainable agricultural practices, such as overgrazing and improper land management, can also contribute to soil erosion and the release of dust particles.
- Excessive water extraction from rivers and groundwater can lower the water table, leading to the exposure of dry and dusty soil.
- The modification of water bodies, such as the construction of dams and reservoirs, can alter natural water flow patterns, potentially drying up rivers and exposing the sediment.
- All these activities increase the vulnerability to sand and dust storms and exacerbate their impacts on human health and the environment.

Conclusion:
Sand and dust storms have far-reaching effects, both in terms of their geographical spread and their impact on human health. It is crucial to address the underlying causes, such as deforestation, unsustainable agricultural practices, and excessive water extraction, to mitigate the risks associated with sand and dust storms. By recognizing the interconnectedness of these issues, we can work towards sustainable solutions that protect both human health and the environment.

In January, Earth is closer to Sun (perihelion) while in July, it experiences aphelion. But due to uneven distribution of land and sea in both hemispheres and air circulation, differences are evened out.

Effects of Temperature Inversion:
Temperature inversion is a weather phenomenon where the normal atmospheric temperature profile is inverted, with a layer of warmer air above cooler air. This can have several significant effects on the environment.

Trapping of Smog:
- One of the major effects of temperature inversion is the trapping of pollutants, such as smog, close to the ground.
- This can lead to poor air quality and health issues for people living in the affected areas.

Cloud Formations:
- Temperature inversion can also lead to the formation of clouds, as the warm air above cools and condenses into water droplets.
- This can result in fog or low-lying clouds that can reduce visibility and affect transportation.

Thunderstorm Prevention:
- Temperature inversion can inhibit the vertical movement of air, which is necessary for the formation of thunderstorms.
- Thunderstorms are less likely to occur in areas experiencing temperature inversion.
Therefore, the correct effects of temperature inversion are cloud formations, thunderstorm prevention, and trapping of smog. Good air quality is not typically associated with temperature inversion as it often leads to poor air quality due to the trapping of pollutants.

Assertion (A): The eastern coasts of continents within the tropics have much heavier rainfall than the interiors of the west coasts.
Reason (R): All western coasts fall in the rain shadow zone.

The correct answer is option 'C', which states that Assertion (A) is correct, but Reason (R) is incorrect.

Explanation:

Eastern Coasts of Continents within the Tropics have Heavier Rainfall:
- The eastern coasts of continents within the tropics, such as the eastern coast of India or the eastern coast of Africa, receive heavier rainfall compared to the interiors of the west coasts.
- This is due to the prevailing wind patterns in the tropics, specifically the trade winds.
- The trade winds blow from east to west in the tropics, carrying moist air from the oceans towards the western coasts of continents.
- As the moist air encounters the landmass, it is forced to rise, leading to the formation of clouds and subsequent rainfall along the western coasts.
- This phenomenon is known as orographic rainfall, where the moist air is lifted over a mountain or elevated terrain, resulting in enhanced precipitation.
- As a result, the western coasts of continents within the tropics receive significant rainfall.

Rain Shadow Zone:
- The rain shadow zone refers to the area that lies on the leeward side of a mountain range or elevated terrain.
- When moist air is lifted over a mountain range, it cools and condenses, leading to rainfall on the windward side of the mountain.
- However, as the air descends on the leeward side, it warms and dries up, resulting in reduced rainfall and arid conditions.
- This creates a rain shadow zone, which is characterized by low precipitation and dry climate.
- The rain shadow effect is prominent on the leeward side of mountain ranges, where the prevailing winds are blocked by the mountains, preventing the moist air from reaching the area.

Reason (R) is Incorrect:
- While it is true that western coasts often experience the rain shadow effect, it is not true that all western coasts fall in the rain shadow zone.
- There are several factors that determine the occurrence of the rain shadow effect, including the direction of prevailing winds, the height and orientation of the mountain range, and the distance from the coast.
- In some cases, the western coasts may not be affected by the rain shadow effect and may receive significant rainfall due to other atmospheric factors or geographical features.

Conclusion:
- The assertion that the eastern coasts of continents within the tropics have heavier rainfall than the interiors of the west coasts is correct.
- However, the reason that all western coasts fall in the rain shadow zone is incorrect, as it does not consider the various factors that determine the occurrence of the rain shadow effect.

Why do rain clouds appear black in colour despite having the Sun above them?

Explanation:
Rain clouds appear black in colour despite having the Sun above them primarily because clouds scatter the light they receive. Let's understand each option given in the question to arrive at the correct answer:

1. Clouds accumulate electrostatic charge:
This option is incorrect as the accumulation of electrostatic charge in clouds does not cause them to appear black in colour.

2. Rain-bearing clouds absorb most of the solar insolation falling on them:
This option is incorrect as rain-bearing clouds do not absorb most of the solar insolation falling on them. Instead, they reflect and scatter a significant portion of the sunlight they receive.

3. Clouds scatter light received by them:
This option is correct. Clouds are made up of tiny water droplets or ice crystals, which act as scattering centers for the incoming sunlight. When sunlight passes through a cloud, the individual water droplets scatter the light in all directions. This scattering of light causes the cloud to appear white or gray to the observer on the ground. However, when rain clouds become thicker and denser, they scatter more light and absorb less, resulting in a darker appearance. The thicker the cloud, the more light it scatters, making it appear darker or even black.

Therefore, the correct answer is option 'D' - 3 only, which states that rain clouds appear black in colour because clouds scatter the light received by them.

In conclusion, rain clouds appear black in colour despite having the Sun above them because of the scattering of light by the water droplets or ice crystals present in the clouds. The thicker and denser the clouds, the more light they scatter, resulting in a darker appearance.

Explanation:
Rainfall patterns are influenced by various factors, including solar insolation, atmospheric circulation, and temperature gradients. When moving from the equator to the poles, there is a general trend of reducing rainfall. This can be explained by the change in solar insolation.

Change in solar insolation:
Solar insolation refers to the amount of solar radiation or sunlight received at a particular location. The intensity of solar radiation decreases as one moves away from the equator towards the poles. This is mainly due to the curvature of the Earth and the angle at which sunlight reaches the surface.

- At the equator, the Sun's rays are more direct, resulting in higher solar insolation. This leads to warmer temperatures and increased evaporation, which in turn contributes to higher rainfall.
- As one moves towards the poles, the angle at which sunlight reaches the surface becomes more oblique. This reduces the amount of solar radiation received, resulting in lower temperatures and decreased evaporation. Consequently, the amount of moisture available for condensation and rainfall decreases.

Other factors:
While solar insolation is the primary factor influencing rainfall patterns from the equator to the poles, other factors can also play a role:

- Atmospheric circulation: The movement of air masses and prevailing winds can affect rainfall patterns. However, in the context of the given options, it is not the main factor responsible for the reducing rainfall pattern.
- Formation of wavy isotherms at the equator: Isotherms are lines on a map connecting points with equal temperature. The formation of wavy isotherms at the equator can result in localized convective rainfall, but it does not explain the general trend of reducing rainfall when moving polewards.
- Movement of the jet stream along the way: The jet stream is a high-speed wind current in the upper troposphere. It can influence weather patterns, but its movement alone does not explain the reducing rainfall pattern.

In conclusion, the primary reason for the reducing rainfall pattern when moving from the equator to the poles is the change in solar insolation. As the angle of sunlight decreases and the amount of solar radiation received reduces, there is less evaporation and moisture available for rainfall.

During the day, this happens.

• So, if you are facing the sea, the wind will strike your face and continue to land.
• During the night, this happens. So, if you are facing the sea, the wind will strike your back and continue to the sea.

Atmospheric pressure is caused by the weight of the atmosphere pushing down on itself and the surface below it. Atmospheric pressure decreases with height above the surface of a planet because there is the less total mass in the atmosphere above a reference point as the height of the reference point increases. This is explained by the heaviness of air closer to the Earth. Air is heaviest at sea level because the air molecules are pressed together due to gravity.

Tyndall effect can be observed when sunlight passes through the canopy of a dense forest. In the forest, mist contains tiny droplets of water, which act as particles of colloid dispersed in the air.

Extratropical Cyclones:
Extratropical cyclones, also known as mid-latitude or frontal cyclones, are large-scale low-pressure systems that occur in the middle and high latitudes outside the tropics. These cyclones are responsible for most of the weather patterns experienced in the middle latitudes, including strong winds, rain, and snow.

Important Features of Extratropical Cyclones:
1. They originate only over the seas or oceans: This statement is incorrect. While many extratropical cyclones do form over the seas or oceans, they can also form over land. Cyclones that form over land are known as continental cyclones. Therefore, this statement is not an important feature of extratropical cyclones.

2. They require a frontal system to get activated: This statement is correct. Extratropical cyclones are typically associated with the interaction of warm and cold air masses, resulting in the formation of a frontal system. The presence of a frontal system is necessary for the development and intensification of extratropical cyclones. Fronts are boundaries between air masses with different temperatures and densities, and the interaction between these air masses leads to the formation of the cyclone.

3. Since they can move only vertically above, they must be carried laterally by jet streams to be effective: This statement is incorrect. Extratropical cyclones are not limited to moving only vertically above. They are characterized by their cyclonic circulation, which involves both vertical and horizontal movement of air. While jet streams can influence the movement and intensity of extratropical cyclones, they are not required for their effectiveness.

Conclusion:
Out of the given statements, only statement 2 is an important feature of extratropical cyclones. These cyclones require a frontal system to get activated and are associated with the interaction of warm and cold air masses. They can form over both land and seas/oceans, and their movement is not limited to vertical displacement above. Therefore, the correct answer is option 'A' (2 only).

Ocean waves do not induce movement of water in the ocean from one place to another. Movement of water is done by ocean currents. If water is not moved from one place to the other, there is no circulation of temperature, nutrients, water density or salinity. So, ocean waves affect the temperature distribution the least. Ocean 'currents’ do. Ocean currents, warm or cold, carry heat/ coolness from one sea region to the other and affect the temperature distribution.

Thunderstorms are formed because of intense convection on moist hot days. Convection refers to the transfer of heat through the movement of fluids, such as air or water. Thunderstorms are a type of weather phenomenon that involves the rapid upward movement of warm, moist air, which eventually leads to the formation of towering cumulonimbus clouds.

Here is a detailed explanation of why thunderstorms form due to intense convection on moist hot days:

1. Introduction to Thunderstorms:
- Thunderstorms are characterized by the presence of cumulonimbus clouds, which are large, dense, and vertically towering.
- These clouds are formed due to the rapid upward movement of warm, moist air.

2. Intense Convection:
- Thunderstorms are primarily formed due to intense convection, which occurs when there is a significant temperature difference between the surface and the upper atmosphere.
- On a hot and moist day, the surface temperature rises, leading to the heating of the lower layers of the atmosphere.
- This heating causes the air near the surface to become warmer and less dense, making it rise rapidly.

3. Updrafts and Downdrafts:
- As the warm air rises, it forms updrafts, which are powerful currents of air moving upward.
- These updrafts carry moisture and heat energy with them as they ascend.
- As the air rises higher into the atmosphere, it cools and condenses, forming cumulonimbus clouds.
- Within these clouds, the rising air cools further, and water droplets and ice crystals start to form, leading to the development of precipitation.

4. Thunderstorm Characteristics:
- Thunderstorms are often associated with heavy rainfall, lightning, strong winds, and sometimes hail.
- The rapid movement of air within the storm system creates strong updrafts and downdrafts, contributing to the formation of severe weather conditions.

5. Moisture Source:
- Moisture is a crucial ingredient for thunderstorm formation.
- On hot days, there is often an abundant supply of moisture available in the lower layers of the atmosphere, which can be provided by sources such as bodies of water, evaporation, or advection from other regions.

In conclusion, thunderstorms are formed due to intense convection on hot and moist days. The rapid upward movement of warm, moist air creates powerful updrafts within cumulonimbus clouds, leading to the formation of thunderstorms. These storms are characterized by heavy rainfall, lightning, and strong winds.

Explanation:

Statement 1: The air pressure is highest at sea level and decreases with height.

This statement is correct. The air pressure at sea level is the weight of the air above a unit area at sea level. As we move up in the atmosphere, the weight of the air decreases, and hence, the air pressure also decreases. Thus, air pressure is highest at sea level and decreases with height.

Statement 2: Low air pressure is generally associated with cloudy skies and wet weather.

This statement is also correct. Low air pressure is associated with unstable weather conditions and the formation of clouds. When the air pressure is low, the air rises, cools, and condenses to form clouds. The condensation of water vapor in the air leads to the formation of precipitation, which can result in wet weather.

Conclusion:

Both statements 1 and 2 are correct. The air pressure is highest at sea level and decreases with height. Low air pressure is associated with unstable weather conditions and the formation of clouds, which can lead to wet weather.

Explanation:

The correct answer is option B: The Earth, in turn, radiates back solar insolation received from the Sun.

Reasoning:

The Earth receives solar insolation from the Sun in the form of electromagnetic radiation. This energy is absorbed by the Earth's atmosphere, land, and oceans. However, the Earth as a whole neither accumulates heat nor loses it due to solar insolation because it radiates back an equal amount of energy into space. This process is known as radiative balance or radiative equilibrium.

Key Points:
- Solar insolation refers to the amount of solar radiation received per unit area on the Earth's surface.
- The Earth's atmosphere plays a crucial role in regulating the amount of solar energy that reaches the Earth's surface. It absorbs some of the incoming solar radiation and reflects or scatters the rest.
- The absorbed solar energy heats up the Earth's atmosphere, land, and oceans. However, this heat is not accumulated indefinitely.
- The Earth radiates energy back into space in the form of longwave infrared radiation. This radiation is emitted by the Earth's surface, the atmosphere, and clouds.
- The rate of energy radiated by the Earth is equal to the rate of energy received from the Sun. This balance between incoming and outgoing radiation is necessary to maintain a stable temperature on Earth.
- If the Earth were to accumulate more energy than it radiates, the temperature would continually increase, leading to a runaway greenhouse effect. Conversely, if the Earth were to lose more energy than it receives, the temperature would continually decrease, resulting in a global cooling effect.
- The maintenance of radiative balance is crucial for the Earth's climate system. It ensures that the Earth's temperature remains relatively stable over long periods.

Therefore, the correct answer is option B: The Earth, in turn, radiates back solar insolation received from the Sun.

Movement of Inter-tropical convergence zone:
The movement of the Inter-tropical convergence zone (ITCZ) is one of the factors that affect the generation and flow of Equatorial Westerlies.

The ITCZ is a low-pressure belt that encircles the Earth near the equator. It is characterized by the convergence of trade winds from the Northern Hemisphere and Southern Hemisphere. The zone moves northward during summer in the Northern Hemisphere and southward during summer in the Southern Hemisphere.

1. During the summer in the Northern Hemisphere, the ITCZ moves northward, resulting in the convergence of trade winds from the Northern Hemisphere and the Equatorial Westerlies. This convergence leads to the generation of Equatorial Westerlies.

2. Similarly, during the summer in the Southern Hemisphere, the ITCZ moves southward, resulting in the convergence of trade winds from the Southern Hemisphere and the Equatorial Westerlies. This convergence also leads to the generation of Equatorial Westerlies.

Coriolis force caused due to the rotation of Earth:
The Coriolis force, which is caused due to the rotation of the Earth, is another factor that affects the generation and flow of Equatorial Westerlies.

The Coriolis force is an apparent force that deflects the motion of objects, including air masses, on the rotating Earth. In the Northern Hemisphere, the deflection is to the right, while in the Southern Hemisphere, it is to the left.

1. The Coriolis force deflects the trade winds from the Northern Hemisphere towards the right, resulting in the formation of Equatorial Westerlies.

2. In the Southern Hemisphere, the Coriolis force deflects the trade winds towards the left, also resulting in the formation of Equatorial Westerlies.

Both 1 and 2:
Therefore, both the movement of the Inter-tropical convergence zone and the Coriolis force caused due to the rotation of the Earth play a role in the generation and flow of Equatorial Westerlies. The movement of the ITCZ leads to the convergence of trade winds, while the Coriolis force deflects these winds to form the Equatorial Westerlies. Hence, option C, "Both 1 and 2," is the correct answer.

Not Related to Formation or Modification of Present Atmosphere

Differentiation is not related to the formation or modification of the present atmosphere.

Explanation:

Formation and modification of the present atmosphere involve various processes that have occurred over millions of years. Some of the significant processes that have led to the formation or modification of the atmosphere are:

1. Solar winds: Solar winds are streams of charged particles that originate from the sun. These solar winds have contributed to the formation of the atmosphere by stripping away the outer layer of the early atmosphere.

2. Degassing: Degassing refers to the release of gases from the Earth's interior. Volcanic eruptions and other tectonic activities have contributed to the release of gases such as carbon dioxide, nitrogen, and water vapor.

3. Photosynthesis: Photosynthesis is the process by which plants convert carbon dioxide and water into oxygen and organic compounds. This process has led to the increase in the concentration of oxygen in the atmosphere.

However, differentiation is not related to the formation or modification of the present atmosphere. Differentiation refers to the process by which the Earth's interior became separated into distinct layers, with the heaviest materials sinking to the core and the lighter materials rising to the surface. This process occurred early in the Earth's history, and it did not have a significant impact on the formation or modification of the atmosphere.

Polar Vortex

The polar vortex is a persistent, large-scale cyclone that circles either of the planet's geographical poles. Here is a detailed explanation of what the polar vortex is:

Definition
The polar vortex is a low-pressure system that is located in the upper atmosphere, typically in the stratosphere, and is centered on the Earth's poles. It is strongest in the winter months and weakens or breaks down in the summer.

Nature
The polar vortex is a natural phenomenon that has always existed, but it has gained more attention in recent years due to its impact on weather patterns and extreme cold outbreaks in certain regions.

How It Forms
The polar vortex forms and is maintained by the temperature difference between the polar regions and the mid-latitudes. This temperature difference creates a strong wind pattern that circles the poles.

Impact on Weather
When the polar vortex weakens or shifts, it can lead to disruptions in the jet stream and result in extreme weather events such as cold outbreaks, heavy snowfall, and even heatwaves in some regions.

Conclusion
In conclusion, the polar vortex is a persistent, large-scale cyclone that plays a crucial role in shaping weather patterns around the world, particularly during the winter months. Understanding the polar vortex is essential for predicting and preparing for extreme weather events.

Explanation:

The correct answer is option 'B' - 2 only.

The doldrums, also known as the Inter-Tropical Convergence Zone (ITCZ), is a region of calm winds and low pressure that is located near the equator. Here is a detailed explanation of each option:

1. Exist at the edge of the tropics:
The doldrums do not exist at the edge of the tropics. They are located near the equator, which is not considered the edge of the tropics. Therefore, option 1 is incorrect.

2. Also known as the Inter-Tropical Convergence Zone (ITCZ):
This statement is correct. The doldrums are also known as the Inter-Tropical Convergence Zone (ITCZ). The ITCZ is a belt of low pressure that encircles the Earth near the equator, where the trade winds from the Northern and Southern Hemispheres converge. The convergence of these winds causes the air to rise, creating a region of low pressure and calm winds. Sailors often refer to this area as the doldrums because the lack of wind makes it difficult to navigate. Therefore, option 2 is correct.

3. Popular for high wind speeds throughout the year:
This statement is incorrect. The doldrums are known for their calm winds, not high wind speeds. Sailors often encounter light, variable, or even stagnant winds in this region, making it difficult to sail through. Therefore, option 3 is incorrect.

In conclusion, the doldrums are known as the Inter-Tropical Convergence Zone (ITCZ) and are characterized by calm winds and low pressure near the equator. Therefore, the correct answer is option 'B' - 2 only.

Explanation:
The westerlies are prevailing winds that blow from west to east in the mid-latitudes. They originate from the subtropical high-pressure belts known as the horse latitudes and move towards the poles. In the Northern Hemisphere, the westerlies are strong due to the presence of large land masses, while in the Southern Hemisphere, they are weaker due to the dominance of oceans.

Therefore, the correct statements are:

1. Westerlies originate in the horse latitudes and move towards the poles.
2. Westerlies move from west to east.

Hence, the correct answer is option A (1 and 2 only).

Introduction:
Coastal places like Kolkata and Mumbai experience humid and moderate weather due to the flowing of sea and land breezes. This phenomenon is influenced by various factors such as proximity to the coast, sea surface temperatures, and prevailing wind patterns.

Sea and Land Breezes:
Sea and land breezes are the primary factors responsible for the humid and moderate weather in coastal places like Kolkata and Mumbai. These breezes occur due to the differential heating and cooling of land and water surfaces.

- Sea Breeze: During the day, the land heats up faster than the sea, causing the air above the land to rise. This creates a low-pressure zone over land. Simultaneously, the sea remains relatively cooler, leading to the formation of a high-pressure zone. As a result, cooler air from the sea moves towards the land, creating a sea breeze. This sea breeze brings moisture from the sea, leading to humid conditions.

- Land Breeze: At night, the situation reverses. The land cools down faster than the sea, causing the air above the sea to rise. This creates a low-pressure zone over the sea and a high-pressure zone over land. Consequently, cooler air from the land moves towards the sea, forming a land breeze. This land breeze carries the moisture from the land, resulting in moderate weather conditions.

Other Factors:
While sea and land breezes play a crucial role in shaping the weather patterns of coastal places like Kolkata and Mumbai, other factors also contribute to their humid and moderate weather.

- Proximity to the Coast: Being located near the coast, Kolkata and Mumbai are influenced by the maritime climate. The presence of large water bodies helps in maintaining moderate temperatures and moisture content in the atmosphere.

- Sea Surface Temperatures: The temperature of the sea surface affects the air temperature and moisture content in coastal areas. Higher sea surface temperatures contribute to the evaporation of water, leading to increased humidity.

- Prevailing Wind Patterns: The direction and strength of the prevailing winds also influence the weather conditions in coastal areas. The interaction between the sea and land breezes and the prevailing winds further enhances the humid and moderate weather experienced in places like Kolkata and Mumbai.

Conclusion:
In conclusion, the flowing of sea and land breezes is the primary reason why coastal places like Kolkata and Mumbai experience humid and moderate weather. The differential heating and cooling of land and water surfaces, along with other factors like proximity to the coast, sea surface temperatures, and prevailing wind patterns, contribute to the overall weather patterns observed in these regions.