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www.atmos-meas-tech-discuss.net/3/2743/2010/
doi:10.5194/amtd-3-2743-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
Aerosol Optical Depth measurements at 340 nm with a Brewer spectrophotometer and comparison with Cimel observations at Uccle, Belgium
Royal Meteorological Institute of Belgium, Ringlaan 3, 1180 Brussels, Belgium
Abstract. The Langley Plot Method (LPM) is adapted for the retrieval of Aerosol Optical Depth (AOD) values at 340 nm from Brewer#178 sun scan measurements between 335 and 345 nm (convoluted with the band pass function of the Cimel filter at 340 nm). The use of sun scans instead of direct sun measurements simplifies the comparison of the AOD values with quasi-simultaneous Cimel values. Also, the intensities are larger at 340 nm due to lower ozone absorption, thus improving the signal to noise ratio. For the selection of the cloudless days, a new set of criteria is proposed. With the new method, individual clear sky AOD values, for which the selection criteria are also presented in this article, are calculated for a period from September 2006 to December 2009. These values are then compared to quasi-simultaneous Cimel measurements, showing a very good linear agreement (the correlation coefficient, the slope and the intercept are, respectively 0.960, 0.992 and 0.005), which proves that good quality observations can be obtained from Brewer sun scan measurements at 340 nm. The seasonal and monthly variability of the Brewer AODs at Uccle are consistent with other studies. The highest values can be observed in summer and spring. More than 50% of the winter AODs are lower than 0.3 whereas in summer, more than 50% of the values are larger than 0.5. On a monthly scale, the lowest AOD are observed in December and the highest values occur in June and April. No clear weekly cycle is observed for Uccle.
Discussion Paper (PDF, 1048 KB) Interactive Discussion (Closed, 10 Comments) Final Revised Paper (AMT)
Notice on Discussion StatusCitation: De Bock, V., De Backer, H., Mangold, A., and Delcloo, A.: Aerosol Optical Depth measurements at 340 nm with a Brewer spectrophotometer and comparison with Cimel observations at Uccle, Belgium, Atmos. Meas. Tech. Discuss., 3, 2743-2778, doi:10.5194/amtd-3-2743-2010, 2010. Bibtex EndNote Reference Manager XML
