Evapotranspiration is the process of evaporating water from leaves through plant transpiration during photosynthesis. The evaporation happens when water vapor leaves the plant surface and transpiration involves the passage of water through a plant. To put it simply, evapotranspiration is combined evaporation and transpiration. It is a main component of the water cycle important in crop maintenance. Factors that affect evapotranspiration include wind, temperature, humidity, soil type, plant type, and water availability. When temperature increases, the rate of evapotranspiration also increases. This is because there is higher amount of energy available for converting liquid water to water vapor. For humidity, if the air is too humid, the transpiration and evaporation rates drop. When it comes to wind, a moving air increases the rate of evaporation and wind also clears humidity produced by plant’s transpiration making the transpiration rate increase. Plants need water, if there is not enough water for plants, there will be no evaporation. They will conserve it instead of transpiring. Soil type is also important as it determines how much water the soil can hold. For areas with vegetative cover, transpiration is higher than evaporation. Plant type is also an important factor because there are plants that don’t transpire much like the succulents, unlike trees and crops that can release huge amounts of water vapor in a day.
Vegetation covers about 20% of the planet. It affects weather and climate as it influences the albedo of the Earth and the amount of greenhouse gases like water vapor and carbon dioxide. Plants release water vapor which is necessary for cloud formation. They also absorb and emit energy that drives the weather. Most plants and forest soils have a very low albedo, and they absorb a large amount of energy. However, plants don’t contribute to overall warming because the excess warm is being balanced by evaporative cooling from transpiration. When it comes to climate, vegetation is important. The process of photosynthesis builds up atmospheric oxygen to the level that is helpful to humans. Plants keep our climate stable by balancing temperature and moisture fluctuations through transpiration. They consume carbon dioxide during photosynthesis which helps lessen the amount of carbon dioxide being released in the atmosphere. Plants and crops are also responsible for the majority of water usage and storage. Without considering irrigation, rain, snow, fog and soil water are all used and absorbed by vegetation. When there is excess water, plants can transpire larger volumes of water which causes evaporative cooling in the atmosphere of the surrounding. There is also a complex relationship between absorption, reflection, transmission and emission of radiation within a vegetated area. It is said that the albedo of a crop is lower than the sum of all the leaves in the canopy and this is due to the differences in angle of solar radiation and crop architecture. The value is also dependent on vegetation type and what time the albedo measurement is taken. Measurements taken during early morning and late afternoon are much higher. Also, albedo measurements in the tropics are less than those of vegetated areas in higher altitudes.
References:
Evapotranspiration. (n.d.). North Carolina Climate Office. https://climate.ncsu.edu/edu/Evap
Vegetation: Its Role in Weather and Climate. (n.d.). North Carolina Climate Office. https://climate.ncsu.edu/edu/Vegetation
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