Test: Water In The Atmosphere - 2 - UPSC MCQ

• Rainfall occurs when the temperature is above 0°C.
• Snowfall occurs when the temperature is below 0°C.
• Sleet occurs when rain falls through a freezing layer near the ground.
• Hailstones form when raindrops pass through very cold layers, freezing into ice pellets.

The weight of water vapor per unit weight of air is called Specific humidity. It is usually expressed as grams of vapor per kilogram of air. The rate of evaporation of water from any surface is directly proportional to the specific humidity, the difference between the surface and the adjoining air.

- The assertion is correct because absolute humidity is indeed the measure of the weight of water vapor in a given volume of air, typically expressed in grams per cubic meter.

- The reason is also correct since relative humidity is defined as the ratio of the current absolute humidity to the maximum possible humidity at that temperature, expressed as a percentage.

- The reason correctly explains the assertion as it elaborates on the concept of moisture in the air, which is integral to understanding absolute humidity.

• Cirrus: These are high-altitude clouds that are thin and wispy in appearance.


• Cumulus: These are puffy, white clouds that often have flat bottoms. They are usually associated with fair weather.


• Stratus: These are low-lying clouds that are uniform and gray in appearance. They often bring overcast skies and light precipitation.


• All of these: This option includes all three types of clouds mentioned above - cirrus, cumulus, and stratus. So, the correct answer is "all of these.

When the excess water vapour condenses directly into solid form it is known as sublimation.

• A. Nimbus clouds are black or dark gray, often dense and opaque.
• B. Dew Point is the temperature at which air becomes fully saturated.
• C. Sublimation is the process where water vapor changes directly into a solid.
• D. Absolute Humidity is the actual amount of water vapor present in the atmosphere.

The correct answer is b) i and iv.

Explanation:

• Statement i is correct: Fog is a type of cloud that forms near or at the ground level, reducing visibility.
• Statement ii is incorrect: Mist contains less moisture than fog, but it can form in various environments, not just over mountains when warm air rises. Mist typically forms when the air near the ground cools.
• Statement iii is incorrect: Nimbus clouds are not thin and white; they are thick, dark clouds associated with precipitation.
• Statement iv is correct: Cumulus clouds are fluffy and resemble cotton wool, typically forming at altitudes between 4,000 to 7,000 meters.

• The assertion is true. Dew does indeed form when moisture condenses on cooler surfaces under conditions of high relative humidity and clear skies.
• The reason is false. Dew can form when the temperature is above freezing, as it is not limited to only conditions at or below freezing.
• Since the assertion is true but the reason is false. Thus, the correct option is Option C.

- Statement i is correct because water is indeed present in the atmosphere in three forms: gaseous (water vapor), liquid (rain, fog), and solid (snow, ice).

- Statement ii is incorrect. Absolute humidity is the actual amount of water vapor present in the air, measured in grams per cubic meter, not a percentage of moisture capacity.

- Statement iii is correct. The dew point is the temperature at which air reaches saturation and can hold no more moisture.

- Statement iv is incorrect. Relative humidity is the percentage of moisture in the air compared to its maximum capacity at a given temperature, not the weight of water vapor per unit volume.

Thus, the correct statements are i and iii, leading to the final answer being A: i and iii.

• Statement i: Incorrect. Evaporation is caused by the absorption of heat, not the loss of heat.
• Statement ii: Correct. Condensation occurs when moist air is cooled to its dew point, leading to the transformation of water vapor into liquid.
• Statement iii: Incorrect. Sublimation is the process where a solid transitions directly to a gas, not the transformation of vapor into liquid.
• Statement iv: Correct. Hygroscopic condensation nuclei, such as dust and salt particles, are essential for condensation as they attract water vapor.

Thus, the correct statements are ii and iv, making Option C (i, ii, and iv) the right choice.

- The assertion is correct as clouds are indeed classified based on their altitude (high, middle, low) and appearance (shape and density).

- The reason is also correct because different types of clouds do signify various weather conditions, with cirrus clouds typically indicating fair weather and nimbus clouds often associated with rain.

- Since the reason explains why the classification exists in terms of weather prediction, it serves as the correct explanation of the assertion. Therefore, Option A is the correct choice.

Cumulus clouds: Cumulus clouds are puffy, white clouds often with flat bases. They are formed at medium to high altitudes, typically between 4000-7000 meters. Cumulus clouds are associated with fair weather, but can also grow into thunderstorms.

• Assertion (A) is correct. Evaporation occurs at a faster rate when the temperature increases, as warmer air can hold more water vapor.
• Reason (R) is also correct. Higher temperatures indeed allow air to retain more moisture, facilitating greater evaporation.
• The reason provided is the correct explanation of the assertion, as it directly supports why increased temperature leads to increased evaporation.
• Therefore, both the assertion and reason are true, and the reason is the correct explanation for the assertion.

• Statement I is false because condensation occurs when air cools and contracts, not when it heats up and expands.
• Statement II is true; condensation can indeed lead to the formation of clouds, dew, frost, or fog.

• Relative Humidity: Relative humidity is the % of moisture present in the atmosphere as compared to its full capacity at a specific temperature. It is expressed as a percentage.


• Relative humidity is calculated by dividing the actual water vapor content by the maximum possible water vapor content at a given temperature and multiplying by 100 to get a percentage.