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Title:
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Reduction of solar radiation by manmade aerosol in Europe: ajoint European project EV5V-CT92-0171
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Author(s):
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Published by:
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Publication date:
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ECN
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1995
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ECN report number:
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Document type:
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ECN-C--95-030
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ECN publication
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Number of pages:
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Full text:
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54
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Download PDF
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Abstract:
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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