The Brewer MKIV spectrophotometer is a modified Ebert grating spectrometer that has been designed to measure the intensity of attenuated solar radiation in the UV and Visible region.

Pointing capabilities of the instrument allow the measurement of direct irradiance, global irradiance, or polarized radiation scattered from the zenith sky. The column amount of atmospheric constituents that absorb or scatter solar or lunar radiation can be determined using differential optical absorption spectroscopy (DOAS) techniques. The atmospheric gases measured by the Brewer using their absorption properties include ozone (O3), sulfur dioxide (SO2), and nitrogen dioxide (NO2). In addition, aerosol optical depth can be determined from measurements of direct solar irradiance.

The most accurate method for determining the total column amount of a gas in the atmosphere is based on the direct sunlight (DS)measurements. It has been shown that the accuracy of measurements taken with a well-maintained Brewer spectrophotometer is 1% in the DS mode and 3%–4% in the zenith sky mode.

The algorithm to retrieve the total ozone column from the BrewerMKIV  in DS mode is based on a differential measurement method involving four selected wavelengths in the ozone absorption spectra, nominally 310.1, 313.5, 316.8 and 320.1nm

The instrument was installed in 1992 and since then O3 and NO2 amounts, and UV irradiances have been systematically collected. Since its installation the Brewer has been calibrated every two years by intercomparison with the same traveling international reference Brewer 017 from International Ozone Services Inc. (IOS). This Brewer is in turn calibrated against the World Brewer Reference Triad in Toronto. In this way the ozone calibration is also traceable to the Brewer Reference Triad.In addition the Brewer data are regularly submitted to the WOUDC (World Ozone and Ultraviolet Radiation Data Centre) and took part to the COST Action ES1207 EUBREWNET (“A European Brewer Network” (EUBREWNET).

Such a long (more than 25 years) data collection of the total ozone content and UV irradiance allow to be used to validate the satellite-derived products, to investigate the long-short term ozone and UV variability, and to investigate the effects on human health induced by changes in exposure to solar UV radiation


Siani, A. M., Frasca, F., Scarlatti, F., Religi, A., Diémoz, H., Casale, G. R., Pedone, M., and Savastiouk, V.: Examination on total ozone column retrievals by Brewer spectrophotometry using different processing software, Atmos. Meas. Tech., 11, 5105-5123,, 2018.


PI: Anna Maria Siani, <a href=”” target=”_blank” rel=”noopener noreferrer”></a>

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