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ECN publication
Reduction of solar radiation by manmade aerosol in Europe: ajoint European project EV5V-CT92-0171
Published by: Publication date:
ECN 1995
ECN report number: Document type:
ECN-C--95-030 ECN publication
Number of pages: Full text:
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Results of a study on the reduction of solar radiation by back-scatteringon manmade aerosol in Europe are presented. A localized study was carried out due to the relatively short residence time of aerosols in the atmosphere which limits the extent of the European aerosol to the European area. The regional character of the aerosol forcing called for a regional investigation which was performed along three lines: (a) measurement of the light-scattering by aerosol components known to be of anthropogenic origin (sulfate and nitrate) in The Netherlands; (b) the trend in solar radiation in Italy, Ireland, Estonia and Germany; (c) calculations of the radiative transfer of solar radiation through the atmosphere with typical continental aerosol. The combined results of the project led to a first indicative value of the reduction in solar radiation in Europe of -3 to -4 W.m"-" 2. This value is based on combining the following results from the subprojects. Nitrate increases the amount of light scattered by aerosol in The Netherlands, compared to the reference compound in the IPCC estimate (sulfate) by a factor of two. Carbonaceous aerosol material seems to have an equally large contribution to the light-scattering. A decrease in the radiation over the last forty years with 3 to 5 % was observed in Italy and in Estonia, while a decrease was absent at a background station in Ireland with predominantly natural marine aerosol. The trend values are indicative of an even higher decrease in solar radiation than the mentioned -3 to -4 W.m"-2. A reduction of solar radiation of order -20 W.m"-2 on cloudless days was deduced from a limited set of measurements in The Netherlands. 1-dimensional modeling of climate parameters with integrated aerosol forcing indicates a local cooling of 1.3 K for the mentioned reduction in solar radiation. The mentioned values have an estimated uncertainty of the same magnitude as the actual values. This is due to the scarcity of relevant data on a constituent which is so variable in time, space and physico-chemical properties. 7 figs., 3 tabs., 3 appendices, 10 refs.

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