GLOBAL ULTRAVIOLET-SPECTRA DERIVED DIRECTLY FROM OBSERVATIONS WITH MULTICHANNEL RADIOMETERS

Some general features of multichannel filter radiometers operating in the UV region of the solar spectrum are reviewed with emphasis on cali bration problems that are due to incomplete knowledge of responsivity in the UV-B region. An alternative calibration procedure that is able to generate a full UV spectrum obtained by a constrained inversion met hod is presented. Accuracy of such spectra is assessed with simulated and with real data. A comparison between customary calibration and an alternative procedure is made in terms of monochromatic UV-B irradianc e and CIE dose rate (CIE is the Commission Internationale de l'Eclaira ge) and indicates that irradiances are estimated within 8% accuracy wi th solar zenith angles as great as 60 degrees and that dose rates are within 6% for any solar zenith angle. The advantage of having an addit ional channel in the UV-B region is considered. (C) 1998 Optical Socie ty of America. OCIS codes: 000.2170, 300.6540, 260.7190, 000.4430.