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Mapping Ozone Conditions Across Europe in Real Time
By Jan Bliki, Technical Coordinator, European Environment Agency, and Tim Haigh, Project Manager, European Environment Agency
Europe has made great strides in reducing air pollution. As a result, most European countries have eliminated winter smog from the burning of coal and reduced levels of acid rain. However, high concentrations of especially fine particulates and ozone still present problems for public health and ecosystems across Europe.
Ozone at high concentrations is a health hazard. It can irritate airways, causing breathing difficulties and damaging lungs after only a few hours of exposure. Up to 30 percent of Europe's urban population is exposed to ozone concentrations above the threshold levels set by the European Union (EU). Ozone pollution is responsible for as many as 20,000 deaths in Europe every year.
When levels of ozone and other air pollutants, such as nitrogen oxides and particulate matter, are high, the pollutants can combine to form harmful smog. However, the highest concentrations of ozone are not always found in urban areas, where the pollutants that form ozone are usually emitted.
Keeping the public informed about ozone pollution is a key part of European legislative strategy to address this air pollution problem.
The ozone Web site that was developed covers 26 European countries and aims to extend coverage to all member countries of the European Environment Agency (EEA) in the near future.
The objective of the site is to provide a visual and easily understandable presentation of air quality measurement data for the public, enabling comparison of air quality conditions across national and regional borders and providing information about local air quality information sites.
"The Web site is an excellent example of how the EU can create partnerships with member countries to serve and empower its citizens," says professor Jacqueline McGlade, executive director of EEA.
The Web site provides the following main features:
About the Data
Data from more than 700 air quality measurement stations in 26 countries across Europe is transmitted to EEA in Copenhagen, Denmark, on an hourly basis. Since the data must be in as real time as possible, the data is displayed as soon as practical after the end of each hour.
The ozone measurement data is provided by national or regional air quality organizations that are responsible for air quality monitoring across Europe. The near real-time data is exchanged across the Internet using a variety of protocols and formats. On acquisition, the data is transformed into a unified XML format and saved to the central database. The data collection and verification system is provided by Microsoft BizTalk Server 2004 to acquire hourly ozone measurements from a number of data providers, transform the data to a unified format, and save the data in the central database.
The central database stores all hourly ozone measurements, interpolated ozone raster datasets, and geographic base data. The database is based on SQL Server 2005 and ArcSDE.
The arrival of new data in the central database triggers the interpolation engine, which loads hourly ozone measurements to create an interpolated estimate of the ozone concentration between measurement stations and saves the resulting raster dataset back to the database.
The station density test is performed to determine if there are large geographic areas for which no ozone measurements are available at any particular hour compared to a reference dataset of ozone-active stations. The interpolation technique used is ordinary kriging with a spherical semivariogram and a 10-kilometer raster resolution. The choice of these parameters offers a good compromise between timeliness, quality, level of detail, and performance. The interpolation engine also estimates the root mean square error (RMSE) of the resulting interpolated ozone surface. The interpolated surface is displayed and stored only if the RMSE is lower than a threshold appropriate for display. The ozone interpolation engine is a Windows service that runs in the background and performs the spatial interpolation of hourly ozone measurements. The interpolation engine was developed in Visual Studio .NET 2003 and ArcObjects.
The ozone data is presented on interactive maps on which ozone concentrations appear as a color-coded surface resulting from the interpolation. At scales greater than 1:10,000,000, a color-coded triangle for the data from measurement stations is displayed.
Image map services combining air quality station information, point measurements, and interpolated ozone surfaces with background data from various sources are provided through ArcIMS technology and connect to the database via ArcSDE.
The site is kept up-to-date with near real-time ozone data (hourly) from more than 40 providers. The site gives data providers, air quality experts, and EU citizens the opportunity to have an overview of the situation on a European level, as well as follow the development of air quality in a specific region and inform users about local air quality information sites. Comparison of air quality conditions across national and regional borders is facilitated.
The ozone Web site (www.eea.europa.eu/maps/ozone/map) is an integrated system to acquire, process, and display air quality data and information that build on existing information and systems in member countries and at the European level. The next steps are to increase awareness and extend the system to other pollutants.
About the Authors
Jan Bliki is project officer for GIS system development, focusing on supporting work on projects to develop the European Environment Agency' spatial information system and data service. Tim Haigh is project manager for information resources with responsibility for projects in the area of public information systems.
For more information, contact Tim Haigh, project manager, EEA (e-mail: firstname.lastname@example.org), or visit www.eea.europa.eu/maps/ozone/map. The authors wish to acknowledge Brendan Killeen (EEA), Geir Endregard (Norwegian Asthma and Allergy Association), Joep Luijten (Atkins Geospatial), and Jesper Skovdal Christiansen (Atkins Denmark).