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Evapotranspiration (ET) refers to the combined processes which move water from the Earth's surface (open water and ice surfaces, bare soil and vegetation) into the atmosphere. [ 2 ] : 2908 It covers both water evaporation (movement of water to the air directly from soil, canopies , and water bodies) and transpiration (evaporation that occurs ...
Various forms of crop coefficients (K c) account for differences between specific vegetation modeled and a reference evapotranspiration (RET or ET 0) standard. Stress coefficients (K s) account for reductions in ET due to environmental stress (e.g. soil saturation reduces root-zone O 2, low soil moisture induces wilt, air pollution effects, and ...
The Penman equation describes evaporation (E) from an open water surface, and was developed by Howard Penman in 1948. Penman's equation requires daily mean temperature, wind speed, air pressure, and solar radiation to predict E. Simpler Hydrometeorological equations continue to be used where obtaining such data is impractical, to give comparable results within specific contexts, e.g. humid vs ...
Precipitation occurs when evapotranspiration takes place and local air becomes saturated with water vapor, and so can no longer maintain the level of water vapor in gaseous form, which creates clouds. This occurs when less dense moist air cools, usually when an air mass rises through the atmosphere to higher and cooler altitudes.
Monthly estimated potential evapotranspiration and measured pan evaporation for two locations in Hawaii, Hilo and Pahala. Potential evapotranspiration is usually measured indirectly, from other climatic factors, but also depends on the surface type, such as free water (for lakes and oceans), the soil type for bare soil, and also the density and diversity of vegetation.
The boiling point of water is the temperature at which the saturated vapor pressure equals the ambient pressure. Water supercooled below its normal freezing point has a higher vapor pressure than that of ice at the same temperature and is, thus, unstable. Calculations of the (saturation) vapor pressure of water are commonly used in meteorology.
Saturated surface dry (SSD) is defined as the condition of an aggregate in which the surfaces of the particles are "dry" (i.e., they will neither absorb any of the mixing water added; nor will they contribute any of their contained water to the mix [11]), but the inter-particle voids are saturated with water.
Water vapour from evapotranspiration mixed with air moves upwards to the point of saturation and then, helped by the emissions of cloud condensation nuclei, forms clouds. Each gram molecule ( mole ) of condensing water will bring about a marked 1200-fold plus reduction in volume.The simultaneous release of latent heat will drive air from below ...