Atmosphere

Statement I: Correct Subtropical and temperate regions have more dust due to dry conditions, sparse vegetation, and strong winds.

Statement II: Incorrect Subtropical and temperate regions have more dry winds, not less, which help lift dust.

Correct Answer: Only Statement I is correct.

Statement I is correct: During the Northern Hemisphere winter (January), isotherms (lines of equal temperature) do not run parallel to latitudes. Instead, they deviate significantly: they bend toward the equator over land and toward the poles over water.

Statement II is correct: Land has a lower specific heat than water, meaning it loses heat much faster. Consequently, in January, the large landmasses of North America and Eurasia are significantly colder than the Atlantic and Pacific Oceans at the same latitude.

The Relationship: Statement II explains Statement I: Because the land is colder than the ocean, a line of constant temperature (isotherm) leaving the warm ocean must "dip" south toward the warmer tropical latitudes to find the same temperature once it hits the cold land. When that same line leaves the cold land and enters the warm ocean, it must "climb" north toward the colder polar latitudes to maintain that same temperature value. Thus, the temperature difference is the direct cause of the bending pattern.

Statement I is correct: Without the atmosphere to trap heat, the Earth's surface temperature would drop to well below freezing, making it too cold to support life as we know it. In statement 1 though it's an extreme statement but from UPSC CSE point of view it's generally considered true.

Statement II is correct: The atmosphere absorbs and retains heat (a natural greenhouse effect), which helps maintain the Earth's average temperature within a habitable range.

Statement III is correct: Gases such as carbon dioxide, methane, and water vapor are particularly effective at absorbing and trapping infrared radiation, helping to warm the planet.

The climate described by these characteristics is most likely a Marine West Coast Climate (Cfb) according to the Köppen climate classification system.

Annual and daily range of temperatures is low: Marine west coast climates are known for their mild temperatures year-round. The influence of the nearby ocean moderates both summer highs and winter lows, resulting in a smaller range of temperatures compared to continental climates at similar latitudes.


Precipitation occurs throughout the year: These regions experience frequent precipitation due to prevailing westerly winds carrying moist air from the ocean. The cyclones associated with these winds bring rain or snowfall throughout the year.

Precipitation varies between 50 cm and 250 cm: The amount of precipitation in marine west coast climates can vary depending on factors like latitude, topography, and proximity to the ocean. The range of 50 cm to 250 cm falls within the typical range observed in these regions.

* Statement-I: Correct - The troposphere is thicker at the equator than at the poles. This is because the equator receives more direct sunlight, leading to warmer temperatures and greater air expansion. This expanded air results in a greater height of the troposphere.

* Statement-II: Correct - Convection is a significant mode of heat transfer in the atmosphere. At the equator, intense solar heating causes air to rise rapidly in strong convectional currents. This rising air carries heat to higher altitudes, contributing to the vertical distribution of heat in the troposphere.

* Statement II directly explains Statement I. The strong convectional currents mentioned in Statement II are the primary reason for the greater thickness of the troposphere at the equator, as explained in Statement I. The rising air due to convection leads to the expansion and increased height of the troposphere in equatorial regions.

Statement 1 is Correct: The Coriolis force is directly proportional to the velocity of the moving object. Therefore, as wind velocity increases, the magnitude of the Coriolis force acting on it also increases, leading to a greater deflection.

Statement 2 is Correct: The Coriolis force is proportional to the sine of the latitude. At the equator (0° latitude), the sine of 0° is zero, so the Coriolis force is absent. At the poles (90° latitude), the sine of 90° is 1 (maximum), making the Coriolis force strongest at these points. It is important to note that while the linear velocity of Earth's rotation is highest at the equator and zero at the poles, the Coriolis effect depends on the rotation of the coordinate system itself, which is most pronounced at the poles.

* Statement 1: Correct - Water vapour is indeed a gas, and its concentration generally decreases with altitude. This is because the air gets colder as we go higher, and colder air has a lower capacity to hold moisture.

* Statement 2: Incorrect - The percentage of water vapour in the atmosphere is highest near the equator and decreases as we move towards the poles. This is because the tropics receive the maximum solar radiation, leading to higher temperatures and more evaporation, which in turn increases the amount of water vapour in the air.

* While it is true that the equator receives more direct sunlight compared to the poles, the actual difference in insolation is not as large as ten times. The difference in insolation between the equator and poles is primarily due to the curvature of the Earth and the tilt of its axis, resulting in varying angles at which sunlight reaches different latitudes.

* Insolation includes various wavelengths, such as visible light, ultraviolet rays, and infrared rays, but infrared rays do not constitute two-thirds of it.

* Water vapour is a greenhouse gas that absorbs infrared radiation emitted by the Earth's surface. This absorption contributes to the greenhouse effect and helps regulate the Earth's temperature. Hence, this is the correct statement.

* Infrared waves are not part of the visible spectrum; they have longer wavelengths than visible light.

Statement 1 is correct. The trade winds in the tropical zone blow from east to west, causing the western sections of the oceans to be warmer than the eastern sections. This is because these winds push the warm surface waters towards the west.

Statement 2 is correct. On the other hand, in the temperate zone, the westerlies blow from west to east. These winds push the warm waters towards the eastern sections of the oceans, making them warmer than the western sections.

Therefore, both statements are correct.


Dewdrops are formed when the temperature drops to the dew point and the air becomes saturated with water vapour.

On a clear night, the Earth's surface loses heat through radiation and can reach a temperature low enough to form dewdrops.

However, on a cloudy night, the clouds act like a blanket, reflecting back the Earth's radiation. This keeps the temperature of the air near the ground warmer, preventing it from reaching the dew point and thus, dewdrops are not formed.

Statement 1 is incorrect. High clouds are often thin and do not reflect very much. They let lots of the Sun's warmth in. They primarily transmit incoming solar radiation. At the same time, they trap some of the outgoing infrared radiation emitted by the Earth and radiate it back downward, thereby warming the surface of the Earth.

Statement 2 is incorrect. Low clouds are often quite thick and reflect lots of sunlight back to space. Low clouds are excellent reflectors. But, they don't stop the longwave energy from escaping to space. Therefore, low clouds help to cool the Earth.


The correct answer is 1 only (Thermal difference between land and water).

Statement 1 is correct: Land heats up and cools down much faster than water. This is because water has a higher specific heat capacity, meaning it takes more energy to heat it up and more energy to cool it down. Coastal areas, being influenced by large water bodies, experience a moderating effect on temperature fluctuations. The temperature changes are more gradual throughout the year.

Statement 2 is incorrect: While altitude can affect temperature (higher altitude generally means cooler temperatures), this is not the primary reason for the difference between continental interiors and coasts. Both continents and oceans have variations in altitude.

Statement 3 is incorrect: Winds can play a role in influencing local temperatures, but their presence wouldn't explain the consistent pattern of higher annual ranges seen in continental interiors.

Statement 4 is incorrect: Rainfall patterns can affect temperature to some extent, but coastal areas often receive more rainfall compared to continental interiors. This wouldn't explain the higher annual range observed inland.

Statement 1 is Incorrect: The westerlies blow between 30° and 60° latitudes in both hemispheres, not between 30° N and 60° S. So, the latitudinal extent mentioned is wrong; it should be 30°–60° N and 30°–60° S.

Statement 2 is Correct: The western disturbances that bring winter rainfall to north-western India originate over the Mediterranean region and are carried by the westerlies. Hence, these moist air masses are indeed part of the westerly wind system.