How do temperature, humidity, wind speed, and solar radiation influence evapotranspiration rates?

How do temperature, humidity, wind speed, and solar radiation influence evapotranspiration rates?

• A. ET decreases with higher temperature and solar radiation.
• B. ET is independent of humidity and wind.
• C. ET only depends on rainfall.
• D. ET increases with higher temperature and solar radiation; decreases with higher humidity; higher wind can enhance ET by removing vapor.

Answer: (D)

Evapotranspiration is driven by energy available at the surface and the atmosphere’s capacity to take up water vapor. Solar radiation provides the energy to heat the surface and fuel evaporation, so more radiation tends to raise ET. Warmer air can hold more water vapor and increases the vapor pressure deficit between the surface and the air, which pulls more water vapor away from leaves and soil, boosting ET. Humidity works in the opposite direction: when the air is already moist (high humidity), the gradient driving evaporation is smaller, so ET decreases. Wind helps by removing the evaporated vapor from right at the surface; stronger winds prevent a humid layer from building up near the surface, maintaining the vapor pressure gradient and increasing ET—assuming water is available. Put together, ET rises with higher temperature and solar input, falls with higher humidity, and can be enhanced by wind through vapor removal, all within the limit set by soil moisture.

Evapotranspiration is driven by energy available at the surface and the atmosphere’s capacity to take up water vapor. Solar radiation provides the energy to heat the surface and fuel evaporation, so more radiation tends to raise ET. Warmer air can hold more water vapor and increases the vapor pressure deficit between the surface and the air, which pulls more water vapor away from leaves and soil, boosting ET. Humidity works in the opposite direction: when the air is already moist (high humidity), the gradient driving evaporation is smaller, so ET decreases. Wind helps by removing the evaporated vapor from right at the surface; stronger winds prevent a humid layer from building up near the surface, maintaining the vapor pressure gradient and increasing ET—assuming water is available. Put together, ET rises with higher temperature and solar input, falls with higher humidity, and can be enhanced by wind through vapor removal, all within the limit set by soil moisture.