Recent advances in signal processing techniques for solar radiometer data

A recent paper, W.H. Erxleben et al. (1996), presented a number of new signal processing techniques for improving the calibration of solar spectral radiometers under conditions of temporally varying optical depths. These techniques, based on correlations and spectral analysis, have been refined and incorporated into an improved calibration scheme. An ozone retrieval routine is also inserted in the scheme, so channels near the peak of the Chappuis band can be included in the processing. The new scheme can be iterated as necessary to increase the accuracy of, and confidence in, the results. Sample results demonstrate the use of the new scheme for calibration of an instrument operated in the Canary Islands during the ACE-2 experiment. Finally, some measurements of the ratio of diffuse skylight to direct sunlight, taken with a customized radiometer, are compared with optical depth measurements to show how addition of an aureole channel can enhance the processing scheme