Comments on ‘correction of errors associated with measurement of net all-wave radiation with double-domed radiometers’ by Oliver and Wright (1990)

Abstract

In their note on correction of measurements with the REBS Q^*4 net radiometer, Oliver and Wright discuss a problem of high general interest, namely that of wavelength-dependent responsivities in net radiometry. They suggest that old measurements can be corrected by a simple addition of 40% of the net longwave radiation. It is shown that this is only the first of two necessary steps needed for a good correction. The 40% value suggested by Oliver and Wright leads to night-time radiation values that are typically 20–25% too negative. It is also suggested that their 40% correction varies with time and place of measurement as well as with the way the radiometer was originally calibrated. This percentage should be replaced by a correction factor based on a design-dependent responsivity difference of around 63% multiplied by a factor depending on the relative importance of longwave and shortwave radiation components prevailing for the measurements to be corrected. The second step in the correction procedure should be a “recalibration” of the signal achieved after equalizing responsivity for negative and positive values of net radiation. It is finally suggested that the cause of the malfunction of the double-dome radiometer has to do with the transmission properties of the polyethylene shield and not with properties of the heat-absorbing surface or entrapped hot air.