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Proceedings Paper

Measurements of O3, SO2, NO2 and HCHO column amounts using a Brewer spectrometer
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Paper Abstract

O3, SO2 and NO2 vertical column amounts and aerosol optical depths at 18 wavelengths from 303 to 363nm were measured daily for the past two years by using a Brewer MK3 double spectrometer in direct-sun mode. The algorithms used are described and compared to the standard algorithm. For O3 and SO2 the standard algorithm was modified by using all 6 measured wavelengths instead of only 4 or 5 and by including a correction for the diffuse irradiance entering the instrument's field of view. This reduces the statistical error of the retrievals by 40% and 50%, respectively, for O3 and SO2. The NO2 retrievals are based on a spectral fitting technique using wavelengths between 349 and 363nm. A 'Bootstrap method' has been developed to calibrate the Brewer for NO2 measurements. This method selects data with lowest NO2-amounts and uses them to derive the needed extraterrestrial solar spectrum. We discuss possible reasons why an intent to apply to same technique for deriving total HCHO columns failed. The main advantage of direct sun methods compared to Differential Optical Absorption Spectroscopy DOAS is that the uncertainty in the air mass factor is significantly smaller. We think that a better correction for the diffuse irradiance entering the instrument's field of view will further improve the retrievals, especially in the low wavelength range (303 to 320nm) used for O3 and SO2.

Paper Details

Date Published: 10 September 2005
PDF: 9 pages
Proc. SPIE 5886, Ultraviolet Ground- and Space-based Measurements, Models, and Effects V, 588602 (10 September 2005); doi: 10.1117/12.620167
Show Author Affiliations
Alexander Cede, Science Systems and Applications, Inc. (United States)
NASA Goddard Space Flight Ctr. (United States)
Jay Herman, NASA Goddard Space Flight Ctr. (United States)


Published in SPIE Proceedings Vol. 5886:
Ultraviolet Ground- and Space-based Measurements, Models, and Effects V
Germar Bernhard; James R. Slusser; Jay R. Herman; Wei Gao, Editor(s)

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