Analysis and interpretation of Aerosol Optical Depth values retrieved from a Brewer spectrophotometer at Uccle, Belgium
De Bock, Veerle
Earth and related Environmental sciences
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The first part of this PhD describes an adapted and improved method for the retrieval of AOD values using sun scan measurements from a Brewer spectrophotometer at 340 nm at Uccle. The retrieved AOD values are subjected to a cloud screening technique and are compared to quasi simultaneous, collocated CIMEL AOD values. The good agreement between both instruments highlights that the Brewer is largely sensitive to AOD at 340 nm and it justifies its use in sun scan mode to expand the AOD retrieval network of instruments. The monthly and seasonal behavior of the retrieved AOD values is also studied in this work and our results agree with results found in literature. The second part of this work focuses on the relation between the erythemal UV dose, global solar radiation, total ozone column and AOD (at 320 nm) at Uccle. Simultaneous measurements of these variables are available at Uccle for a time period of 25 years (1991– 2015) and this time series is long enough to allow for reliable determination of significant changes. Different analysis techniques are combined to allow for an extensive study of the relations between the variables. First, a change point analysis is performed to determine whether there are sudden changes in our time series (of either natural or instrumental origin). Linear trends are calculated for the monthly anomalies time series of the variables and changes in the minimum and maximum values and in the frequency distribution are also investigated. Finally, a multiple linear regression technique is applied to investigate the relation between the erythemal UV dose, global solar radiation, total ozone and AOD (at 320 nm) at Uccle in order to increase our understanding of observed changes in UV radiation at Uccle.