AN IMPROVED NET-RADIATION INSTRUMENT

An improved net-radiation instrument for measuring the net flux of radiant energy through a surface parallel to the earth's surface, which employs the principle of exposing a ventilated radiation-absorbing element to the radiation sources, is described. The importance of providing similar ventilation on both sides of the absorbing plate is pointed out, and the control features to insure this uniformity are described. A method of reducing the error due to the variation of the absorptivity of the blackened surface with wave-length is discussed. The performance of the instrument and the possible errors are described. It was found that the instrument is capable of giving net-radiation measurements accurate to within two per cent.