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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 ...
The total transport rate of the species is then given by a summation of the Stefan flow and diffusive contributions. An example of the Stefan flow occurs when a droplet of liquid evaporates in air. In this case, the vapor /air mixture surrounding the droplet is the flowing fluid, and liquid/vapor boundary of the droplet is the interface.
In mathematics and its applications, particularly to phase transitions in matter, a Stefan problem is a particular kind of boundary value problem for a system of partial differential equations (PDE), in which the boundary between the phases can move with time.
A variety of evaporation pans are used throughout the world. There are formulas for converting from one type of pan to another and to measures representative of the environment. [5] Also, research has been done about the installation practices of evaporation pans so that they can make more reliable and repeatable measurements. [6]
The measurements range from under 30 to over 120 inches per year. Formulas can be used for calculating the rate of evaporation from a water surface such as a swimming pool. [5] [6] In some countries, the evaporation rate far exceeds the precipitation rate. Evaporative cooling is restricted by atmospheric conditions.
Evaporation is an essential part of the water cycle. The sun (solar energy) drives evaporation of water from oceans, lakes, moisture in the soil, and other sources of water. In hydrology, evaporation and transpiration (which involves evaporation within plant stomata) are collectively termed evapotranspiration. Evaporation of water occurs when ...
The Blaney–Criddle equation is a relatively simplistic method for calculating evapotranspiration. When sufficient meteorological data is available the Penman–Monteith equation is usually preferred. However, the Blaney–Criddle equation is ideal when only air-temperature datasets are available for a site.
In technical terms, the dew point is the temperature at which the water vapor in a sample of air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates. [7] At temperatures below the dew point, the rate of condensation will be greater than that of evaporation, forming more liquid water.