**2. Background**

Air pollution in large cities is one of the major issues to be addressed by local and global communities due to its widespread presence, and deleterious impact on human life (Hadji‐ mitsis, 2009). As air pollution is a major environmental health risk, by reducing the levels of air pollutants, countries will reduce the incidence of disease from respiratory infections, heart disease and lung cancer (WHO, 2011). Actions by policy makers and public authorities at the national, regional and international levels are required in order to control the exposure to air pollutants (EEA, Air Quality in Europe, 2012 - Report). Transboundary domestic air pollution is of high concern among the EU member states. In 2010, about 21% of the EU urban population was exposed to concentrations of PM10 above the limit value established by the European Environmental Agency (EEA, Air Quality in Europe, 2012 - Report). The WHO, USEPA (U.S. Environmental Protection Agency) and EEA have established an extensive body of legislation which establishes standards and objectives for a number of air pollutants such as PM10 (coarse particles), PM2.5 (fine particles) and O3 (WHO, Fact sheet No 313, 2011; USEPA, NAAQS, 2012; EEA, AAS, 2012).

Current research focused on the study of regional and intercontinental transport of air pollutants, such as particulate matter (PM10, 2.5), points to a need for additional data sources to monitor air pollution in multiple dimensions, both spatially and temporally. To address this issue, earth observations from satellite sensors can be a valuable tool for monitoring air pollution due to their ability to provide complete and synoptic views of large areas.

Although air quality monitoring stations have been established in major cities, there is an increased need to establish mobile stations for additional coverage, as such stations provide a means for alerting the public regarding air quality. However, measuring stations are localised and do not provide sufficient geographic coverage, since air quality is highly variable spatially. The use of earth observations to monitor air pollution in different geographical areas, espe‐ cially cities, has received considerable attention from researchers (see Wald et al., 1999; Grosso and Paronis, 2012; Hadjimitsis, 2009; Hadjimitsis et al., 2010; Jones and Christopher, 2007; Michaelides et al., 2011; Nisantzi et al., 2012; Retalis and Sifakis, 2010; Retalis et al., 2003; Retalis et al., 1999; Vidot et al., 2007). Several researchers (Chudnovsky et al., 2013; Gupta et al., 2006; Koelemeijer et al., 2006; van Donkelaar et al., 2010) have focused on the use of satellite sensors on air pollution studies, especially their ability for systematic monitoring and synoptic coverage. The use of sunphotometers and LIDAR systems are found to be suitable tools for assisting the air pollution monitoring studies (Ansmann et al., 2012; Amiridis et al., 2008; Engel-Cox et al., 2006; Papayannis et al., 2007a,b; Pitari et al., 2013). This study presents the integrated use of satellite remote sensing, sunphotometers and LIDAR for monitoring air pollution in Cyprus.
