Explanation of the criteria for classification and numbering of components     C46.1.03
   (MAR 99)
Explanation of the dates on the component's description



1.   Purpose and objectives

     To measure daily free water surface evaporation.

2.   Description

     The class A evaporation pan has a diameter of 1200 mm and a depth of 255 mm. Change of water level is measured with a hook gauge and vernier in a stilling well in the pan. Daily evaporation is computed as the change in water level plus the depth of rainfall during the period.

3.   Input

     Solar energy.

4.   Output

     Daily totalized evaporation.

5.   Operational requirements and restrictions

     The class A evaporation pan can be manufactured in a mechanical workshop. It should be mounted in an open site, free of obstacles with the bottom of the pan supported on a wooden frame, allowing air to circulate freely underneath. Screening is necessary to prevent animals and birds drinking the water.

6.   Form of presentation

     Constructional drawings at a scale of 1:20.

7.   Operational experience

     The class A evaporation pan has been manufactured in the Thai Meteorological Department and successfully used in Thailand.

8.   Originator and technical support

     Instrument Repair and Accessories Manufacture Section, Thai Meteorological Department.

9.   Availability

     From the HOMS National Reference Centre for Thailand.

10.  Conditions on use

     Cost of reproduction and mailing.


(First entered: 26 AUG 83

Last updated: 8 JAN 86)