The quantity of evaporation from the surface of water is measured or observed in an experimental tank under measured or seen meteorological and cultural circumstances. The term "evaporative loss" refers to the loss of water vapor through transpiration by plants and animals, respiration, and other means. It does not include precipitation or runoff.
An evaporative loss tank is a device used for measuring the rate at which water is lost by evaporation. The tank should be large enough to allow the researcher to make several accurate measurements over time. The tank must also be covered so that excess heat and sunlight do not influence the results.
Water loss by transpiration is important for many reasons. First, it is one of the main methods by which plants gain oxygen for photosynthesis. Second, it plays a role in soil biology - both as a source of nutrients and as a way of removing pollutants from the environment. Transpiration can also have an impact on climate - either by increasing or decreasing global temperatures.
Water loss by transpiration varies depending on many factors such as humidity, temperature, plant type, and size. In general, the total amount of water loss will be equal to the difference between input and output.
Evapotranspiration, abbreviated as ET, is the combination of evaporation and transpiration. Actually, the quantity of water consumed by a landscape is equal to the amount of water lost to deep percolation and runoff plus the evapotranspiration of the individual plants. Deep percolation is the process where soil moisture moves downward through the profile until it reaches a depth at which there is no further movement due to surface tension or other factors. Runoff is the discharge of water from the land's surface either as liquid or as steam.
ET can be calculated using the Penman-Montieth equation: ET in mm/day = 0.5 * D * (0.6 * WL + c), where D is the daily average air temperature in degrees Celsius, WL is the weekly average latent heat in joules/kg*°C, and c is a constant. For example, if the daily average air temperature is 15 °C and the weekly average latent heat is 1,500 joules/kg*°C, then ET is about 120 mm/day.
Plants use energy from the sun to produce their food gas carbon dioxide, which becomes part of the plant tissue. Some of this carbon dioxide is released into the atmosphere immediately, but most is stored in the plant tissue over time. When plants die, they decompose, releasing their carbon back into the atmosphere.
Evaporation—the process by which water converts from a liquid to a gas—from oceans, seas, and other bodies of water (lakes, rivers, and streams) accounts for almost 90% of the moisture in our atmosphere, according to studies. The remaining 10% is from precipitation. Water vapor is the primary gas that carries energy through the atmosphere, helping to regulate climate around the world.
Ocean waters evaporate more than land surfaces because they are moister and warmer. As water evaporates, it loses some of its weight as vapor, leaving less water behind to fill up with more liquid again. This effect adds up over many thousands of miles of ocean and leads to overall global warming.
Land surfaces are also responsible for some global warming via the same process of evaporation but only if the heat from the ground rises into the atmosphere. Otherwise, any water lost by evaporation would just return to earth in the form of rain or snow. For example, when you sweat on a hot day, you are losing water out of your body into the air but some of it returns back into your body through your skin. Land surfaces can't lose all of this water because that would lead to desertification and people would die! So some of it stays in the atmosphere until it turns into rain or snow. This is called the atmospheric reservoir effect.
Evaporation (the conversion of liquid water to water vapor) and transpiration (the emission of water vapor from plant surfaces) are water budget outflow processes. Evapotranspiration (ET) is the result of a combination of water surface evaporation, soil moisture evaporation, and plant transpiration. Water that evaporates from lakes, rivers, and oceans and also from saturated soils and vegetation goes into the hydrologic cycle. The amount of this lost water is called ET.
Water that reaches the ground as precipitation or as runoff from other areas flows into streams, rivers, and lakes. It becomes part of the hydrologic cycle there until it evaporates or is absorbed by plants or into the soil.
The term "evapotranspiration" was first used by Hackel in 1938 to describe the exchange of water between the land and atmosphere. He showed that most of the water evaporating from lakes, ponds, and seas is reabsorbed by the land via atmospheric rivulets and raindrops. This is because the average air temperature near bodies of water is less than the dew point temperature, so water vapor will condense out as droplets when it passes over cold objects such as ice or clouds. As it changes form from a liquid to a gas, some of its mass is lost to other particles within the atmosphere. This loss reduces the density of the surrounding air which then causes more precipitation to fall.
Evaporation is the process by which an element or compound transitions from its liquid to gaseous form below the boiling point; specifically, the process by which liquid water enters the atmosphere as water vapour....
Evaporation, as defined by children, is the process of converting from a liquid to a vapor. There are two main types of evaporation: physical and chemical.
Physical evaporation occurs when heat energy is released due to the conversion of liquid to gas. This happens when water evaporates into the air around it. Heat energy is needed to make this happen; without it, the water would still be liquid. The heat comes from the sun and other sources such as heat radiation from clouds and ground objects. Physical evaporation is also called dry evaporation because only moisture and some small molecules such as H2O are present in the gas phase. Dry evaporation is important for removing harmful substances such as pollutants that can lead to acid rain or ozone depletion.
Chemical evaporation takes place when atoms or molecules gain or lose electrons. These particles are ejected from the liquid and become gas molecules. Chemical evaporation can be good or bad depending on which elements are lost or gained during this process. For example, if hydrogen ions are ejected then chemical evaporation is called acidification. If oxygen ions are ejected then chemical evaporation is called oxidation.