|WORLD METEOROLOGICAL ORGANIZATION||
|Explanation of the criteria for classification and numbering of components||
|Explanation of the dates on the component's description|
COMPUTING SHALLOW LAKE EVAPORATION USING CLASS A PAN DATA
1. Purpose and objectives
To calculate daily evaporation loss from shallow lakes, ponds, and
reservoirs using data from a nearby standard Class A Evaporation Pan.
The method is based on the equation derived by Kohler, Nordenson and
Fox (1955) used to correct the evaporation loss from a Class A evaporation
pan for heat advection through the pan sides and bottom. The resulting corrected "lake evaporation" values are applicable to nearby small water
Daily measurements from a standard Class A evaporation pan installation including: pan water loss or gain, pan water temperature,
screen air temperature, wind run at 15 cm above the pan rim, and the depth of rainfall, if any. The station elevation is also required.
Estimate of daily evaporation loss for small water bodies.
5. Operational requirements and restrictions
Applicable only to small water bodies with negligible heat storage
(typically with area 5 km2 and depth 10 m). The accuracy of the estimates
increases with the accumulation period, i.e. monthly estimates based on an
accumulation of daily values are more reliable than the individual daily
6. Form of presentation
The procedure is given in the form of a simple algorithm which can be programmed into a computer or programmable calculator.
7. Operational experience
The procedure has been applied in Canada since 1970.
8. Originator and technical support
Hydrometeorology and Marine Division
10. Conditions on use
Free of charge; acknowledgement of source is expected.
|(First entered:18 MAY 87||
Last updated: 14 DEC 1999)