Without water, life as we know it would be impossible. More than 97% of the Earth’s water is salt water in the oceans. As a matter of fact, only a tiny portion of our total water “budget” is in our atmosphere at any given moment.
For an analogy of Earth’s total water budget, let’s say one liter of water represents of Earth’s water. The ocean would account for slightly greater than 97% of that liter. To be exact, 972 milliliters (one milliliter equals one thousandth of a liter). All of Earth’s fresh water equals the remaining 28 milliliters. If we break up the remaining 28 milliliters into smaller slices, we find water locked up as ice equaling 23 milliliters, underground fresh water 4 milliliters, surface fresh water about 2 big drops (as water in lakes and rivers), and lastly one very small drop as water in the soil and the air. As you can see, what makes up our atmosphere and surface water tables is literally a drop(s) in the bucket when it comes to the total water budget. However, as we know, that very small amount has a very large impact.
Earth’s “balancing” act with respect to the water cycle works like this: About 4,200 billion gallons of water fall on land as precipitation on any given day. Think of this as 4.2 gallons of precipitation from a 40-gallon bathtub. An average of 2,800 billion gallons evaporate from land into the air each day. This is like putting 2.8 gallons back into the bathtub. This leaves about 1,400 billion gallons to soak into the ground or to run down rivers back to the oceans. If nothing else happened, the atmosphere would be missing this 1,400 billion gallons at the end of each day. Our 40-gallon bathtub would be low. The tub (our atmosphere) never runs dry because water evaporating from the oceans and carried by winds over the land makes up the difference.
The ongoing process of evaporation and condensation is what the precipitation process is all about. In the process of going from one stage to another (vapor to liquid, or vice versa, for example), tremendous energy is either used or stored in the atmosphere. Water vapor acts like a reservoir of potential energy. The energy is “stored” in the vapor, only to be released during the condensation process. The acts of going from invisible vapor to visible liquid, i.e., condensation, releases the stored energy in the form of heat. As a matter of fact, this heat release is a major driver of thunderstorm and hurricane development.