Pan evaporation is a measurement that combines or integrates the effects of some climatic elements: temperature, humidity, precipitation, drought dispersion, solar radiation, and wind. Biggest evaporation occurs on a hot, windy, dry, sunny day; and greatly reduced when the clouds block the sun and when the air is cool, calm, and moist. Measurement of pan evaporation allows farmers and ranchers to understand how much water their plants need.
Video Pan evaporation
Evaporation panor
An evaporation pan is used to hold water during observation for the determination of the amount of evaporation in a particular location. Such pots have various sizes and shapes, most commonly used in circular or square shapes. The most famous of the pots is a "Evaporating Class" and "Sunken Colorado Pan" evaporating pot. In Europe, India and South Africa, Pan Symbol (or sometimes Symon Tank) is used. Often an automatic evaporation pan with a water level sensor and a small weather station are located nearby.
Maps Pan evaporation
Standard methods
Various vapor pans are used all over the world. There is a formula for converting from one type of pot to another and for measuring environmental representation. Also, research has been done about the evaporation pots installation practices so they can make more reliable and repeatable measurements.
Class A evaporation pot
In the United States, the National Weather Service has standardized its size in Class A evaporation pot , a cylinder with a diameter of 47.5 inches (120.7 cm) with a depth of 10 inches (25 cm)). The pans rest on a carefully laid wooden base and are often covered by chain fences to keep animals from drinking. Evaporation is measured daily because the water depth (in inches) evaporates from the pan. The day of measurement begins with a pan filled exactly two inches (5 cm) from the top of the pan. At the end of 24 hours, the amount of water to refill the pan to exactly two inches from its peak is measured.
If the settling occurs within a 24-hour period, it is taken into account in calculating the evaporation. Sometimes the rainfall is greater than evaporation, and the measured water dimension should be dipped from the pot. Evaporation can not be measured in a Class A pot when the water surface of the pan is frozen.
Class A Evaporation Pan is very limited to use on days with rainfall & 30mm (rain gauge 203mm) unless it is discharged more than once every 24 hours. Analysis of daily rainfall and evaporation readings in areas with regular showcases of heavy rain show that almost without fail, on days with rainfall over 30mm (203mm Rain Gauge) daily evaporation is excessively higher than the days another in the same month in which the condition is more accepting of applicable evaporation.
The most common and obvious error is in daily rainfall events & gt; 55mm (rain gauge 203mm) where the Class A Evaporating pot is likely to overflow.
The less obvious, and therefore more apprehensive, is the influence of heavy or intense rain that causes a very high amount of daily evaporation without obvious overflow.
Sunken Colorado pan
The Colorado pan basin is square, 1 m (3 ft) on the sides and 0.5 m (18 in.) Inside and is made of unpainted galvanized iron. As the name suggests, it is buried in the ground into about 5 cm (2 inches) from the rim. Evaporation of the Sunken Pan Harvest can be compared with a Class A pot using a conversion constant. The pan coefficient, on a yearly basis, is about 0.8.
Pan Evolution Reduced Evolution
Over the past 50 years, pan evaporation has been carefully monitored. For decades, the measurement of pot evaporation was not critically analyzed for long-term trends. But in the 1990s scientists reported that the rate of evaporation decreased. According to the data, downtrend has been observed worldwide except in some places where it has increased.
It is currently theorized that, all other things are equal, as the global warming climate of evaporation will increase proportionately and as a result, the hydrological cycle in the most general sense will accelerate. The decreasing trend of pan evaporation has also been attributed to a phenomenon called global dimming. In 2005 Wild et al. and Pinker et al. found that the trend of "dimming" has reversed since around 1990
Another theory suggests that measurements do not take into account the local environment. As local moisture levels rise in the local area, less water evaporates from the pan. This leads to incorrect measurement and must be compensated in data analysis. A model that calculates for a global humidity estimate of additional local matches.
Evaporating vs. Lake Pan Evaporation
Pan evaporation is used to estimate evaporation from the lake. There is a correlation between the evaporation of the lake and the evaporation pan. Evaporation of the body's natural water is usually at a lower level because the body of water does not have a metal side that becomes hot with the sun, and while the penetration of light in the pot is essentially uniform, the penetration of light in the natural body of the water will decrease. as an increase in depth. Most textbooks suggest multiplying the pan evaporation by 0.75 to correct this.
Relationship to the Hydrological Cycle
"It is generally agreed that the evaporation of the pot has declined over the last half century in many areas of the Earth, but the significance of this negative trend, related to terrestrial evaporation, is still somewhat controversial, and its implications for the global Hydrologic cycle are unclear. from alternative views that these evaporative changes are generated, either from global radiation dimming, or from complementary relationships between pan and terrestrial evaporation.In fact, these factors are not mutually exclusive but act simultaneously. "
See also
See also
- Atmometer (evaporimeter)
- Hydrology
External links
- Hastings, Nebraska, Office (April 15, 2010). "Evaporation Station". National Weather Service . Retrieved January 6 2013 . CS1 maint : Multiple names: author list (link)
References
Source of the article : Wikipedia
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