Behind the Forecast: Evapotranspiration - plant sweat and your forecast

LOUISVILLE, Ky. (WAVE) - Evapotranspiration is responsible for 15% of our atmosphere's water vapor.

Evapotranspiration is the combination of evaporation and transpiration. Both processes release water vapor, which is a crucial part of our planet's water cycle, into the atmosphere.

Transpiration occurs when plants release water vapor from their stomata, tiny holes in their leaves. They expel water vapor as part of photosynthesis and the conversion of carbon dioxide into oxygen. Transpiration helps plants' leaves cool down in the sun's heat.

Evaporation transpires when water changes from liquid water to water vapor. It doesn't matter if it happens on your skin or in the middle of an ocean, the term evaporation still applies.

Evapotranspiration is affected by the following:

• Humidity: If the air is too humid, transpiration and evaporation rates slow down. Since there's a lot of moisture already in the air, less of it is pulled from other sources.
• Wind Speed: Stronger winds help to increase evaporation rates. Transpiration also increases as the wind clears nearby humidity produced by a plant from the immediate area.
• Temperature: In hotter temperatures, evaporation and transpiration both increase. More energy is available in the atmosphere when it's hotter for liquid water to be converted to water vapor. Transpiration also increases because plants open stomata and expel more water vapor.
• Plant Type: Trees and certain crops can release incredible amounts of water each day. An oak tree can release 40,000 gallons of water vapor each year; that's more than 100 gallons of water every day. An acre of corn can release 4,000 gallons of water in a day.
• Soil Type: The type of soil influences how much water it can hold and how easily water can be pulled from it.
• Water availability: Evaporation is unlikely when soil is dry. During drier conditions, plants will conserve water instead of releasing it during transpiration.

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