Solutions-Class 8-Geography-Chapter-3-Humidity and Cloud-Maharashtra Board

(1) Cirrus - Higher altitude - Snowflake clouds.

(2) Cumulonimbus - Vertical extent in the sky - Roaring clouds

(3) Nimbostratus — Low altitude — Continuous rainfall.

(4) Alto-cumulus - Medium altitude - Floating clouds.

The Vapour-holding capacity of air is dependent on the temperature of air.

The amount of vapour in 1 cu.m. of air shows the Absolute humidity

As relative humidity is less in desert areas, the air is dry there.

Cumulonimbus type of clouds are indicators of storm

In a free environment, the condensation of the vapour present in the atmosphere takes place around dust particles.

The air in a region is dry due to the low amount of moisture in the air.

Absolute humidity : The amount of water vapour in 1 cu.m. of air is called the absolute humidity. It is measured with the help of the following formula :

Absolute humidity = \(\frac{\text{mass of water vapour}}{\text{volume of air}}\)

Relative humidity : The amount of water vapour present in air expressed as a percentage of the amount needed for saturation at the same temperature is called relative humidity. It is measured with the help of the following formula :

Relative humidity (%) = \(\frac{absolute\,\,humidity}{vapor\,holding\,capacity}× 100\) 

High relative humidity and dew point temperature of the air are the prerequisites for condensation.

Cloud : A visible mass of fine particles of ice and water accumulated around the dust particles in the air at high altitude is called a cloud.

Types of clouds :

• High clouds : Clouds at an altitude of 7000 m to 14000 m are considered as high clouds. Cirrus, Cirro-Stratus and Cirro-Cumulus are high clouds.
• Medium clouds : Clouds at an altitude of 2000 m to 7000 m are considered as medium clouds. Alto-Stratus and Alto-Cumulus are medium clouds.
• Low clouds : Clouds at an altitude of less than 2000m are considered as low clouds. Strato-Cumulus, Stratus, Nimbostratus, Cumulus and Cumulonimbus are low clouds.

Nimbostratus and cumulonimbus type of clouds give rain.

The relative humidity percentage depends on the absolute humidity and vapour-holding capacity of the air at a given temperature.

The condensed water or fine particles of snow accumulate around dust particles at high altitude leading to formation of clouds. The condensed water or fine particles in the clouds are almost weightless. Therefore, clouds float in the sky.

• At sea level, the temperature is determined to be rather high. The moisture-holding capacity of air around sea level is found to be considerable due to high temperatures. As a result, the humidity of the air at sea level is rather high.
• Temperatures have been observed to be relatively low at high altitude places. The moisture-holding capacity of air at high altitude is determined to be limited due to the low temperature. As a result, the humidity of the air at high altitude is relatively low.

As a result, the proportion of relative humidity varies with height.

At a particular temperature, the moisture-holding capacity of air is exhausted and equals the proportion of moisture contained in it. The air can no longer absorb any additional moisture at this point. As a result, the air gets saturated.

• Cumulus clouds are found between 500 m to 6000 m altitude. They are mostly formed due to the vertical flow of the air.
• Sometimes, the vertical expanse of the cumulus clouds increases and it leads to formation of huge mountain-like cumulonimbus clouds. Thus, cumulus clouds change into cumulonimbus clouds.

Relative humidity (%) = \(\frac{absolute\,\,humidity}{vapor\,holding\,capacity}× 100\) 

                                 =  \(\frac{18}{30.37}× 100\)

                                 = 59.26%

Absolute humidity = \(\frac{\text{mass of water vapour}}{\text{volume of air}}=\frac{4.08}{1}\) = 4.08 gm/m³