CORRECTING GLOBAL SOLAR ULTRAVIOLET-SPECTRA RECORDED BY A BREWER SPECTRORADIOMETER FOR ITS ANGULAR RESPONSE ERROR

We present a methodology for correcting the global UV spectral measure ments of a Brewer MKIII spectroradiometer for the error introduced by the deviation of the angular response of the instrument from the ideal response. This methodology is applicable also to other Brewer spectro radiometers that are currently in operation. The various stages of the methodology are described in detail, together with the uncertainties involved in each stage. Finally global spectral UV measurements with a nd without the application of the correction are compared with colloca ted measurements of another spectroradiometer and with model calculati ons, demonstrating the efficiency of the method. Depending on waveleng th and on the aerosol loading, the cosine correction factors range fro m 2% to 7%. The uncertainties involved in the calculation of these cor rection factors were found to be relatively small, ranging from simila r to 0.2% to similar to 2%. (C) 1998 Optical Society of America.