In what weather conditions do your clothes dry faster? A hot, dry, windy day, or a cool, cloudy, rainy day? Why do you use a blow drier to dry your hair? Water evaporates faster if the temperature is higher, the air is dry, and if there's wind. The same is true outside in the natural environment.

Evaporation rates are generally higher in hot, dry and windy climates. The rate at which water evaporates from any surface, whether from a lake's surface or through the stomata on a plant's leaf, is influenced by climatic and weather conditions, which include the solar radiation, temperature, relative humidity and wind and other meteorological factors. Evaporation rates are higher at higher temperatures because as temperature increases, the amount of energy necessary for evaporation decreases.

In sunny, warm weather the loss of water by evaporation is greater than in cloudy and cool weather. Humidity, or water vapor content of the air, also has an effect on evaporation.

The lower the relative humidity, the drier the air, and the higher the evaporation rate. The more humid the air, the closer the air is to saturation, and less evaporation can occur. Also, warm air can "hold" a higher concentration of water vapor, so you can think of there being more room for more water vapor to be stored in warmer air than in colder air.

Wind moving over a water or land surface can also carry away water vapor, essentially drying the air, which leads to increased evaporation rates. So, sunny, hot, dry, windy conditions produce higher evaporation rates. We will see that the same factors - temperature, humidity, and wind - will affect how much water plants use, which contributes to how much water we use to produce our food!

Evaporation requires a lot of energy and that energy is provided by solar radiation. The maps below Figure 4. Notice how the amount of solar radiation available for evaporation varies across the US. Solar radiation also varies with the season and weather conditions. Note that annual evaporation rates are given in inches per year. For example, Denver, Colorado in the lake evaporation map is right on the line between the inches and inches per year of lake evaporation, so let's say 40 inches per year.

On average, if you had a swimming pool in Denver, and you never added water and it didn't rain into your pool, the water level in your pool would drop by 40 inches in a year. No additional source of energy is required for evaporation, and the water does not need to reach the boiling point to evaporate. What you just read implies that evaporation, but not boiling, is a natural process.

Your puddle of water or the water on your hair that you just washed will evaporate without you doing anything special. Just wait, and it dries. But boiling does not usually happen naturally.

We have to deliberately heat the liquid to get it to boil. Your eggs will cook just as fast either way. On the other hand, evaporation of water will cool the water—and any surface that the water is evaporating off of. The evaporating water molecules carry away heat from your skin.

This is also why you perspire on a hot, summer day. The additional moisture on your skin results in more evaporation, which cools your skin. Because at high altitudes, the air pressure is lower. Any cooks out there? I just picked up my old copy of Joy of Cooking, in which the authors include how cooking instructions must be modifi ed at high altitudes.

Remind me to do an article on that. Clothes drying on a clothesline will dry faster on a summer day than in winter.

If you step out of an outdoor swimming pool when the wind is blowing, you feel colder because the wind causes the water to evaporate faster from your skin, carrying away heat energy from your skin faster, leaving your skin colder Figure 4.

The wind causes that moisture to evaporate faster, carrying away more heat from your skin. Water evaporates faster when the air is dry.

When the air is dry, there are fewer water molecules in the air returning to the liquid, so the water evaporates faster. When the air has many water molecules in it i. Try this investigation: Put an equal amount of water in three identical jars. In climates where the humidity is low and the temperatures are hot, an evaporator cooler, such as a "swamp cooler" can lower the air temperature by 20 degrees F.

As this map shows, evaporative coolers work best in the dry areas of the United States red areas marked A and can work somewhat in the blue areas marked B. In the humid eastern U. Here is Fido, looking both sharp and cool as he sports the latest in fashionable dog apparel that also keeps him cool on a hot day. Fido is wearing a "cooling vest", where the owner wets it down, places it on the dog, and the properties of the evaporation process help the dog stay comfortable.

Yes, swamp coolers aren't just for homes anymore. After all, the evaporative process is just as happy keeping a dog cool as it is keeping a house cool. Evaporative coolers are really quite simple devices, at least compared to air conditioners. Swamp coolers pull in the dry, hot outdoor air and pass it through an evaporative pad that is kept wet by a supply of water.

In a home device, a fan draws the air through the pad, the water in the pad evaporates, resulting in cooler air which is pumped through the house. Much less energy is used as compared to an air conditioner. Source: California Energy Commission. Earth's water is always in movement, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth.

Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years. The air is full of water, even if you can't see it.

Higher in the sky where it is colder than at the land surface, invisible water vapor condenses into tiny liquid water droplets—clouds. When the cloud droplets combine to form heavier cloud drops which can no longer "float" in the surrounding air, it can start to rain, snow, and hail What is streamflow?

How do streams get their water? To learn about streamflow and its role in the water cycle, continue reading. Perhaps you've never seen snow. Or, perhaps you built a snowman this very afternoon and perhaps you saw your snowman begin to melt. Regardless of your experience with snow and associated snowmelt, runoff from snowmelt is a major component of the global movement of water, possibly even if you live where it never snows.

The atmosphere is the superhighway in the sky that moves water everywhere over the Earth. Water at the Earth's surface evaporates into water vapor which rises up into the sky to become part of a cloud which will float off with the winds, eventually releasing water back to Earth as precipitation. The air is full of water, as water vapor, even if you can't see it.

Condensation is the process of water vapor turning back into liquid water, with the best example being those big, fluffy clouds floating over your head. And when the water droplets in clouds combine, they become heavy enough to form raindrops to rain down onto your head. You can't see it, but a large portion of the world's freshwater lies underground.

It may all start as precipitation, but through infiltration and seepage, water soaks into the ground in vast amounts. Water in the ground keeps all plant life alive and serves peoples' needs, too.

Note: This section of the Water Science School discusses the Earth's "natural" water cycle without human Runoff is nothing more than water "running off" the land surface. Just as the water you wash your car with runs off down the driveway as you work, the rain that Mother Nature covers the landscape with runs off downhill, too due to gravity. Runoff is an important component of the natural water cycle.