Water at the surface of the ocean, rivers, and lakes may evaporate and migrate into the atmosphere with a little help from the sun, a process known as evaporation. Evapotranspiration can move large amounts of water vapor from the oceans to the continents. It also plays a role in regulating Earth's temperature by preventing heat-absorbing liquid water from being lost to space.
Evaporation occurs when water molecules lose their bonds with other molecules or particles so they are free to rise into the air. The two main types of evaporation are atmospheric evaporation and plant transpiration. Atmospheric evaporation happens when moisture in the air is in contact with hot objects such as roadways during the day. This movement of moisture into the air is what makes clouds. At night time, when roads are cold, atmospheric evaporation slows down. Plant transpiration is the evaporation of water from plants. Some plants, like trees, have very large leaves that cover a lot of area. These plants can transpire a large amount of water vapor into the atmosphere. Smaller plants need more water to survive so they transpire less water than larger plants.
The water source for evaporation isn't limited to terrestrial surfaces. Water from the ocean may evaporate directly into the atmosphere or flow inland before doing so.
Water evaporates off the surface of lakes and seas due to solar heat. This converts the liquid water in the atmosphere to water vapor. Plants, too, help water enter the atmosphere via a process known as transpiration. Snow and ice may also release water into the sky. The water vapor then condenses with other particles in the air causing clouds to form.
Lakes are often referred to as "lungs of the earth" because they absorb carbon dioxide from the atmosphere and slowly release it back into it when they flow over submerged rocks. The oceans have absorbed about half of all the CO2 that has been added to the atmosphere by humans. That means that if there were no more water in the oceans, it would be much hotter than it is today for its altitude.
The Earth's water cycle is one of the most important processes in nature. It controls the amount of moisture in the planet's atmosphere and determines where we get our rain and snow. Water is responsible for many interesting things we can't even imagine right now (like the creation of silicon-based life). And it's essential for human survival. Without water, there would be no way for us to live.
Some scientists believe that some lakes are able to sink down deep enough so that water flows under ground between them and the sea. These are called subterranean lakes or aquifers.
Instead of melting, some frozen water converts to water vapor gas and escapes into the atmosphere in a process known as sublimation. Water vapor can travel great distances before it condenses again.
The movement of water vapor from one place to another depends on how hot it is where it originates and how cold it is where it ends up. If it's hot, it will rise; if it's cold, it will fall.
For example, if water vapor rises from the ocean to become clouds, it will then release its energy by radiation when it reaches the cooler atmosphere above the ocean. The temperature reduction caused by moving from the warmer ocean to the colder atmosphere causes the rising water vapor to change back into a liquid phase. When this newly formed cloud droplets freeze out at the top of the cloud, ice crystals form that fall as snow or rain back to the Earth's surface.
Water vapor can be transported long distances by winds. A wind with a strong direction and speed can act like a pump, transporting vapor away from places where it is coming from and bringing it closer in proximity to regions where it can condense.
Also, currents can transport vapor between oceans and continents.