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<article language="en">
	<journal>
		<journal_title>Atmospheric Chemistry and Physics Discussions</journal_title>
		<journal_url>www.atmos-chem-phys-discuss.net</journal_url>
		<issn>1680-7367</issn>
		<eissn>1680-7375</eissn>
		<volume_number>10</volume_number>
		<issue_number>4</issue_number>
		<publication_year>2010</publication_year>
	</journal>
	<doi>10.5194/acpd-10-10925-2010</doi>
	<article_url>http://www.atmos-chem-phys-discuss.net/10/10925/2010/</article_url>
	<abstract_html>http://www.atmos-chem-phys-discuss.net/10/10925/2010/acpd-10-10925-2010.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys-discuss.net/10/10925/2010/acpd-10-10925-2010.pdf</fulltext_pdf>
	<start_page>10925</start_page>
	<end_page>10968</end_page>
	<publication_date>2010-04-23</publication_date>
	<article_title content_type="html">Multi-annual changes of NO&lt;sub&gt;x&lt;/sub&gt; emissions in megacity regions: nonlinear trend analysis of satellite measurement based estimates</article_title>
	<authors>
		<author numeration="1" affiliations="1,2">
			<name>I. B. Konovalov</name>
			<email>konov@appl.sci-nnov.ru</email>
		</author>
		<author numeration="2" affiliations="2">
			<name>M. Beekmann</name>
		</author>
		<author numeration="3" affiliations="3">
			<name>A. Richter</name>
		</author>
		<author numeration="4" affiliations="3,4">
			<name>J. P. Burrows</name>
		</author>
		<author numeration="5" affiliations="3">
			<name>A. Hilboll</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Institute of Applied Physics, Russian Academy of Sciences, Nizhniy Novgorod, Russia</affiliation>
		<affiliation numeration="2" content_type="html">Laboratoire Inter-Universitaire de SystÃ¨mes AtmosphÃ©riques, CNRS, UMR7583, UniversitÃ© Paris-Est and UniversitÃ© Paris 7, CrÃ©teil, France</affiliation>
		<affiliation numeration="3" content_type="html">Institute of Environmental Physics and Remote Sensing, IUP/IFE, University of Bremen, Bremen, Germany</affiliation>
		<affiliation numeration="4" content_type="html">Center for Ecology and Hydrology, Wallingford, UK</affiliation>
	</affiliations>
	<abstract content_type="html">Hazardous impact of air pollutant emissions from megacities on atmospheric
composition on regional and global scales is currently an important issue in
atmospheric research. However, the quantification of emissions and related
effects is frequently a difficult task, especially in the case of developing
countries, due to the lack of reliable data and information. This study
examines possibilities to retrieve multi-annual NO&lt;sub&gt;x&lt;/sub&gt; emissions changes
in megacity regions from satellite measurements of nitrogen dioxide and to
quantify them in terms of linear and nonlinear trends. By combining the
retrievals of the GOME and SCIAMACHY satellite instrument data with
simulations performed by the CHIMERE chemistry transport model, we obtain
the time series of NO&lt;sub&gt;x&lt;/sub&gt; emission estimates for the 12 largest urban
agglomerations in Europe and the Middle East in the period from 1996 to
2008. We employ then a novel method allowing estimation of a nonlinear trend
in a noisy time series of an observed variable. The method is based on the
probabilistic approach and the use of artificial neural networks; it does
not involve any quantitative a priori assumptions. As a result,
statistically significant nonlinearities in the estimated NO&lt;sub&gt;x&lt;/sub&gt; emission
trends are detected in 5 megacities (Bagdad, Madrid, Milan, Moscow and
Paris). Statistically significant upward linear trends are detected in
Istanbul and Tehran, while downward linear trends are revealed in Berlin,
London and the Ruhr agglomeration. The presence of nonlinearities in
NO&lt;sub&gt;x&lt;/sub&gt; emission changes in Milan, Paris and Madrid is confirmed by
comparison of simulated NO&lt;sub&gt;x&lt;/sub&gt; concentrations with independent air quality
monitoring data. A good quantitative agreement between the linear trends in
the simulated and measured near surface NO&lt;sub&gt;x&lt;/sub&gt; concentrations is found in
London.</abstract>
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