A typical cumulus cloud having a volume of 1 km3 can weigh approximately 3.3 million pounds (1525 tons). The weight of the clouds depends on the cloud liquid water content value and other factors such as temperature and pressure. Clouds at higher altitudes such as cirrus clouds have a lower mass than that of cumulonimbus clouds.
How heavy are clouds?
Have you ever imagined the weight of a typical fluffy cloud suspended in the sky? The average weight of a typical cloud can be more than 1 million pounds (500 tons). However, note that the mass calculation of the cloud is not that straightforward because we can’t simply use a weighing machine to calculate it. In order to estimate the mass of clouds, we need to understand the composition of the clouds and other factors affecting it.
Read: 🌧️ How Do Clouds Form?
How do you weigh a cloud?
Cloud is a fluffy mass that is composed of water droplets and air. Therefore, to weigh the cloud, we need to determine the density of water droplets in the cloud. There are several techniques to measure the water droplets density or liquid water content of clouds.
Cloud liquid water content (LWC) is the measure of liquid water present in a cloud and can be expressed in g/m3. Note that it does not include solid water such as ice crystals. LWC varies from cloud to cloud depending upon their type and location. Some clouds such as cirrus clouds have low density while cumulonimbus clouds have high LWC.
Read: 🌦️ Why Are Clouds White?
One of the techniques uses an electrically heated wire to measure the LWC. This wire is kept outside of the airplane. As the airplane moves through the cloud, the electrically heated wire comes in contact with the water droplets of the clouds. These water droplets start to evaporate due to heat dissipation from the wire. Electrical power is measured in order to maintain the constant temperature of the wire. This power reading is converted LWC value.
Another technique involves the phenomenon of light scattering. An instrument is used to measure the scattering light from water droplets. Then, this value is converted to the LWC value.
Here is typical value of LWC for various clouds
| Cloud Type | LWC (g/m3) | Altitude (feet) |
| cirrus | .03 | 16,500-45,000 |
| fog | .05 | below 6,500 feet |
| stratus | .25-.30 | below 6,500 feet |
| cumulus | .25-.30 | below 6,500 feet |
| stratocumulus | .45 | below 6,500 feet |
| cumulonimbus | 1.0-3.0 | below 6,500 feet |
To estimate the weight of a cloud, we need to calculate the sum of the weight of water droplets and the weight of air. The weight of water droplets can be calculated using LWC values. However, note that the weight of water droplets and air can vary with different temperatures and pressure. We can calculate the approximate weight of a cloud with the following assumptions
- Assuming the weight of air as 1.225 kg/m³
- LWC values for different clouds based on the above table
- Assuming the volume occupied by water droplets is negligible.
The weight of a cloud equals the multiplication of cloud volume (m3) with the sum of the weight of water droplets and the weight of the air inside the cloud.
Read: 🌨️ How Do Clouds Float?
How much does a cumulus cloud weigh?
Cumulus is the cotton-like clouds that are found in the altitude range of 1,000–6,500 ft. These clouds have a cloud liquid content value of about 0.25-.3 g/m3. Cumulus clouds can be stretched over long distances (over 300 miles or 480 km) and height can be in the altitude range of 1600 ft to 7900 ft.
To know how heavy cumulus cloud are, let’s take a cumulus cloud with 1 cubic kilometer (km3) volume.
Weight of cumulus cloud = 1*1000,000,000 m3 * (0.3 + 1.225) g/m3
= 1,525,000,000 g
Therefore, a 1 km3 cumulus cloud can weigh about 1.5 million kilograms (3.3 million pounds or 1525 tons)
How much does a rain cloud weigh?
The mature cumulonimbus clouds are responsible for causing rainfall. These rain clouds are also known as thunderheads. These cumulonimbus clouds have LWC in the range of 1-3 g/m3.
Let’s calculate the weight of 1 km3 rain cloud (cumulonimbus cloud).
Weight of Cumulonimbus cloud = 1*1000,000,000 m3 * (3 + 1.225) g/m3
= 3,225,000,000 g
Therefore, a 1 km3 Cumulonimbus cloud can weigh about 3.2 million kilograms (7 million pounds or 3175 tons)
How much does a cirrus cloud weigh?
Cirrus clouds are found at higher altitudes (16,500-45,000) and also have a low liquid water content density of about 0.03 g/m3.
Let’s take 1 km3 volume of cirrus cloud to calculate its mass.
Weight of cirrus cloud = 1*1000,000,000 m3 * (0.03 + 1.225) g/m3
= 1,235,000,000 g
Therefore, a 1 km3 cirrus cloud can weigh about 1.2 million kilograms (2.64 million pounds or 1200 tons).
References
Thompson, Anne (2007). “Simulating the Adiabatic Ascent of Atmospheric Air Parcels using the Cloud Chamber”. Department of Meteorology, Penn State.
Wallace, John M.; Hobbs, Peter V. (2006). Atmospheric Science: An Introductory Survey (2nd ed.). U.K. Elsevier Inc. ISBN 012732951X
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