Humidity and Clouds | Class 8 | Geography | Chapter 3| Maharashtra State Board
Explore the fascinating world of weather, humidity, and cloud formations in this comprehensive geography lesson. Understand the processes of evaporation, condensation, and precipitation, and learn how different cloud types influence weather patterns. Perfect for students looking to deepen their understanding of meteorological concepts.
Questions & Answers
1. Match the column and complete the chain:
A | B | C | |
(A) | Cirrus | (i) Vertical extend in the sky | (a) Roaring clouds |
(B) | Cumulonimbus | (ii) higher altitude | (b) Floating clouds |
(C) | Nimbostratus | (iii) Medium altitude | (c) continuous rainfall |
(D) | Alto-cumulus | (iv) Low altitude | (d) snow flake clouds |
Ans.
A | B | C | |
(A) | Cirrus | (ii) higher altitude | (d) snow flake clouds |
(B) | Cumulonimbus | (i) Vertical extend in the sky | (a) Roaring clouds |
(C) | Nimbostratus | (iv) Low altitude | (c) continuous rainfall |
(D) | Alto-cumulus | (iii) Medium altitude | (b) Floating clouds |
2. Choose the correct word from the brackets and complete the sentences:
(Cumulonimbus, relative humidity, absolute humidity, condensation, vapor-holding capacity)
a. The ………….. of the air is dependent on the temperature of the air.
Ans. The vapour-holding capacity of the air is dependent on the temperature of the air.
b. The amount of vapour in 1 cu.m, of air shows the ………….
Ans. The amount of vapour in 1 cu.m, of air shows the absolute humidity.
c. As …………. is less in the desert areas, the air is dry there.
Ans. As relative humidity is less in the desert areas, the air is dry there.
d. ……………. type of clouds are indicators of the storm.
Ans. Cumulonimbus type of clouds are indicators of the storm.
e. In a free environment, the ………….. of the vapour present in the atmosphere takes place around the dust particles.
Ans. In a free environment, the condensation of the vapour present in the atmosphere takes place around the dust particles.
3. Differentiate between:
a. Humidity and clouds
Ans.
Aspect | Humidity | Clouds |
Defination | Amount of water vapour in the air | Visible masses of condensed water vapour or ice |
Visibility | Invisible | Visible |
Role in weather | Affects temperature and precipitation | Formed when air becomes saturated; can lead to precipitation |
Measurement | Measured in grams per cubic meter or % (RH) | Observed and classified by type and altitude |
b. Relative humidity and Absolute humidity
Ans.
Aspect | Relative humidity | Absolute humidity |
Defination | Percentage of actual moisture relative to maximum it can hold at temperature | Actual amount of water vapour in air (g/m³) |
Expression | Expressed as a percentage | Measured in grams per cubic meter (g/m³) |
Dependence on Temperature | Varies with temperature | Does not depend on temperature |
Commonly Used in | Weather forecasting and comfort levels | Assessing actual water vapour content |
c. Cumulus clouds and Cumulonimbus clouds
Ans.
Aspect | Cumulums clouds | Cumulonimbus clouds |
Appearance | Fluffy, white and dome shaped | Dense, towering and dark |
Weather indicator | Generally fair weather | Stroms, heavy rain and lightning |
Altitude | Low to moderate (500-6000m) | Tall, often reaching high altitudes |
Rainfall | Rarely brings rain | Often brings heavy rain and sometimes hail |
4. Answer the following questions:
(a) Why is the air in a region dry?
Ans. The air in a region is dry if the relative humidity is low, often due to high temperatures and low moisture sources, as in desert areas.
(b) How is humidity measured?
Ans. Humidity is typically measured in grams per cubic meter (absolute humidity) or as a percentage (relative humidity).
(c) What are the prerequisites for condensation?
Ans. Low temperature and high relative humidity are required for condensation, where the air reaches its dew point and moisture condenses around dust particles.
(d) What is a cloud? Write its types.
Ans. A cloud is a visible mass of condensed water vapor or ice suspended in the atmosphere. Types include high clouds (cirrus, cirrostratus, cirrocumulus), medium clouds (altostratus, altocumulus), and low clouds (stratus, stratocumulus, nimbostratus).
(e) Which type of clouds give rain?
Ans. Nimbostratus and cumulonimbus clouds are primarily associated with rainfall.
(f) On what does the percentage of relative humidity depend?
Ans. It depends on the temperature and the amount of moisture in the air, decreasing as temperature rises and increasing when moisture levels rise or temperature drops.
5. Give geographical reasons:
(a) Clouds float in the sky:
Ans. Clouds float because the condensed water droplets and ice particles in them are very fine and nearly weightless, allowing them to stay suspended in the atmosphere with the help of vertical air currents.
(b) The proportion of relative humidity changes according to altitude:
Ans. As altitude increases, air temperature decreases, reducing its moisture-holding capacity, which in turn affects relative humidity.
(c) Air becomes saturated:
Ans. Air becomes saturated when it holds the maximum amount of water vapor possible at a given temperature, reaching 100% relative humidity.
(d) Cumulus clouds change into cumulonimbus clouds:
Ans. When warm air continues to rise, the cumulus clouds expand vertically due to updrafts, accumulating moisture, and eventually forming cumulonimbus clouds associated with thunderstorms.
6. Solve the following:
(a) When the temperature of the air is 30° C, its vapour-holding capacity is 30.37 gms/ cu.m. If absolute humidity is 18 gms / cu.m. then what would be the relative humidity?
Ans.
Relative Humidity =
(Absolute Humidity ÷ Vapour-holding capacity) ×100
Given, Absolute Humidity = 18 gms/cu.m., Vapour-holding capacity = 30.37 gms/cu.m.
Relative Humidity = (18 ÷ 30.37) ×100 ≈ 59.3%
(b) What would be the absolute humidity of air if 1 cu.m. air contains 4.08 gms of vapour at 0°C temperature?
Ans.
Given that 1 cu.m. of air contains 4.08 gms of vapor at 0°C, the absolute humidity is 4.08 gms/cu.m.
E X T R A
1. Examine the following statements and correct the incorrect ones:
a. Cumulonimbus clouds are the indicators of the pleasant atmosphere.
Ans.
Incorrect.
Corrected: Cumulonimbus clouds are indicators of thunderstorms and stormy weather.
b. The relative humidity is found to be high in desert region.
Ans.
Incorrect.
Corrected: The relative humidity is found to be low in desert regions.
c. The high temperature of the air leads to rapid evaporation.
Ans.
Correct - The high temperature of the air leads to rapid evaporation.
d. When the humidity in the air is 0 gm/cu.m. at any temperature, the air is said to be humid.
Ans.
Incorrect.
Corrected: When the humidity in the air is 0 gm/cu.m. at any temperature, the air is said to be dry.
e. Cirrostratus appears like a bed sheet with wrinkles.
Ans.
Correct - Cirrostratus clouds appear like a bed sheet with wrinkles.
2. Answer the following questions in brief:
a. Write in brief about the features of high clouds.
Ans.
Features of High Clouds
Altitude: Formed at very high altitudes, usually between 7,000 to 14,000 meters.
Types: Include Cirrus, Cirrostratus, and Cirrocumulus clouds.
Appearance: Generally thin and wispy, often ice-crystal-based due to cold temperatures at high altitudes.
Weather Indication:
High clouds typically indicate fair weather but can signal a change in the weather, especially when Cirrostratus clouds appear before a warm front.
b. Write in brief about the features of medium clouds.
Ans.
Features of Medium Clouds
Altitude: Found at moderate altitudes, typically between 2,000 to 7,000 meters.
Types: Include Altostratus and Altocumulus clouds.
Appearance: Altostratus clouds often form uniform grey or bluish layers that cover the sky, while Altocumulus appear as white or grey patches in layers or groups.
Weather Indication: These clouds can indicate changing weather and sometimes bring light precipitation if they thicken.
c. Write in brief about the features of Strato-Cumulus, Stratus and Nimbostratus.
Ans.
Features of Strato-Cumulus, Stratus, and Nimbostratus
Strato-Cumulus: Low-altitude clouds with layers or clusters that appear white to grey; often have rounded patches and rarely produce rain.
Stratus: Feature a uniform, greyish layer that covers the sky like a blanket, often resulting in overcast conditions. These clouds may produce light drizzle or mist.
Nimbostratus: Thick, dark, and continuous clouds at low levels, usually bringing steady, prolonged rain or snowfall.
d. Write about the features of Cumulus and Cumulonimbus.
Ans.
Features of Cumulus and Cumulonimbus
Cumulus: Large, fluffy, dome-shaped clouds with a white, bright appearance; indicate fair weather and form at low to mid-altitudes (500-6000 meters). They are typically associated with good weather.
Cumulonimbus: Towering, dense, and dark clouds that form from cumulus clouds with vertical development; indicate severe weather, including thunderstorms, lightning, and heavy rainfall. They are often accompanied by hail and can reach great altitudes, sometimes extending through the entire troposphere.
3. Give geographical reasons for the following:
a. The absolute humidity of air in coastal regions is higher than the humidity of air in inland areas.
Ans.
Coastal regions are close to large bodies of water, like oceans and seas, which provide a constant source of moisture through evaporation. This increases the absolute humidity in the coastal air. Inland areas lack this large water source, leading to lower absolute humidity levels.
b. The absolute humidity of air in equatorial regions is higher than the humidity of air in polar regions.
Ans.
The equatorial region experiences high temperatures and receives direct sunlight throughout the year, which promotes rapid evaporation from water bodies. This leads to higher moisture levels and, consequently, higher absolute humidity. In contrast, polar regions are cold with limited evaporation, resulting in lower absolute humidity.
c. Damp air is found in the coastal regions.
Ans.
Coastal regions have abundant moisture due to the proximity of seas and oceans. Warm temperatures in these regions also increase evaporation rates, leading to high moisture content in the air, which makes the coastal air feel damp.
d. Dry air is found in the inland regions.
Ans.
Inland areas are far from large water bodies, so there is limited moisture available for evaporation. Additionally, in hot inland regions, any moisture in the air is quickly absorbed by the warm, dry ground, leading to low humidity levels and dry air.
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