The Sun and the Water Cycle

Science Center Objects

Who's the boss? The real boss of the water cycle doesn't even live here on Earth. The sun is what makes the water cycle work. The sun provides what almost everything on Earth needs to go—energy, or heat.

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Water cycle components  »  Atmosphere  ·  Condensation  ·  Evaporation  ·  Evapotranspiration  ·  Freshwater lakes and rivers  ·  Groundwater flow  ·  Groundwater storage  ·  Ice and snow  ·  Infiltration  ·  Oceans  ·  Precipitation  ·  Snowmelt  ·  Springs  ·  Streamflow  ·  Sublimation  ·  Surface runoff

The sun is so big that even at over 90 million miles you can feel its heat. The sun's energy affects water at its smallest level - the molecular level. Liquid water contains water molecules stuck together. The energy from the sun can break apart these tightly-held molecules into much smaller sets of water molecules, which results in tiny water vapor particles, an invisible gas. This process allows liquid water to evaporate into water vapor, which in the main way water gets from the land surface and oceans back into the sky.

The sun and the water cycle

Credit: NASA

Even in a dry desert environment, the water cycle is taking place. If you look at a picture of a real desert–no, the Sahara Desert will do, but Antarctica at the bottom of the world is even more of a desert. This place actually gets less precipitation than the Sahara does! The inner regions of Antarctica gets only about 2 inches of precipitation per year. The winds here blow up snow from the land and put it into the atmosphere, which is part of the water cycle. And the sun helps out, too, causing sublimation to occur, which causes snow to evaporate directly into water vapor gas.

The sun also participates in moving water around the Earth. Different parts of the world (and even your neighborhood) are heated to different levels by the sun, and unequal heating and cooling of parts of the landscape causes air to move around from here to there—the winds. You know that the winds move clouds and the weather all over the place; all of this mixing up and moving is an important part of the water cycle.