Correction of UVS-AB-T UV Radiometers Using a Radiative Transfer Model

Observation of UV radiation is of major importance to human health and to the calculation of photochemical reaction rates. However, the sensitivity of UV radiometers decays because of equipment aging. A correction method is therefore proposed by using a decrement formula that is approximately a quadratic function of time and is obtained by fitting the clear-sky observation data from an aged UVS-AB-T UV radiometer with the data simulated by the Tropospheric Ultraviolet and Visible (TUV) radiative transfer model. The corrected data from the older radiometer are verified by the data from another newer radiometer on selected clear-sky days. The results show a high correlation and a low bias between the radiometers, and the mean of the corrected data from the older radiometer is 94.5% of that from the newer radiometer. After a long time of use, the decrement of the observation data would increase dramatically and errors of the data after correction would still be significant. In Dongguan, China, a recommendation is made that a UV radiometer should not be used for more than 5 years when the decrement rate reaches 50%.