The amount of water inside a cloud is not different from the amount of water in the clear air around it.
However, while the clear air contains water vapor, inside the cloud the air is saturated with water vapor and it has condensed out to produce the cloud.
The difference between the two states is caused by temperature differences rather than the water content.
The color of a cloud doesn’t make much difference either.
In the higher part of a cloud, the water is in the form of ice crystals. Lower down it is a mixture of ice and liquid water. The color of the cloud depends mainly on this ice/water mixture and the size of the water droplets, and less on the total amount of water.
An estimate of a cloud’s water content can be obtained from the amount of rain the cloud can produce.
If the entire atmosphere were saturated with water and it all fell in a steady stream, this could produce some 1.4 inches of rain, while the thickest actual clouds produce about 0.8 inches.
Cloudbursts can produce 2 inches or more, but this requires additional moisture from the surrounding atmosphere, which means such events are localized.
The heaviest cloudbursts roughly follow the following equation: the rainfall in inches equals 162.5 multiplied by the square root of the time in minutes that it has been raining.
A more typical shower produces a fraction of an inch of rain, at a rate of perhaps 0.04 inches per minute. Normally 1 inch of rain corresponds to 900,000 cubic feet of water weighing 4,000 tons per cubic miles of cloud, though the thickest clouds can contain up to 20 times as much.
You can also estimate the amount of water from the volume of the cloud.
By volume, the fraction of the cloud filled with water is about 1 millionth, or 0.0001 percent. The cross-section area of a cloud can be measured from its shadow. A small cloud 1,000 feet by 1,000 feet and 500 feet high has a volume of 500 million cubic feet, of which roughly 500 cubic feet will be water, weighing 15 tons.
Even if you can’t calculate the precise amount of water in a cloud, these numbers may still impress your friends.
Sadly, just looking at a cloud does not give very precise information about how much water it contains.
The color of a cloud depends entirely on the relative position of the viewer and the physical structure of the cloud. Its apparent size is dependent on the altitude of the cloud, and this is generally very difficult to judge from a single observation point.
But knowing exactly how much water is contained in a cloud is important for producing accurate weather forecasts.
The choice of frequency for a Doppler radar beam is very important.
If the beam interacts too strongly with the water in a cloud, in terms of either reflecting or attenuating the signal, then the radar will have only a limited ability to penetrate cloud structure. If the interaction with water is too weak, then no useful information can be returned at all.
One facility in England can analyze and extract a huge variety of data and has a maximum range of around 100 miles. It is able to provide information on droplet density, size, speed, and whether the droplets are water or ice.
Using this tool, your reader could work out fairly accurately the total water content contained within a cloud and, from the structure of the cloud, how likely it is to start raining, this technique has proved very useful at the Wimbledon tennis championships in past years, which are, of course, notorious for being interrupted by downpours.
Such radars help to produce detailed information on weather, from tracking hurricanes to helping to produce your daily weather forecast and predicting areas of turbulence on aircraft flights.
And remember that kinetic energy rises with the square of the velocity.