The land - use / cover data were extracted from the pan - European component of the Copernicus land monitoring service ( CLMS , 2020 ) . In particular , the CORINE land cover ( CLC ) dataset for the year 2012 was used ( Corine Land Cover , 2012 ) . To better understand the urban surface characteristics surrounding each monitoring station , a squared buffer zone of 1 km 2 spatial resolution was created and the dominant CLC category within each buffer zone was computed and assigned to the respective site . The 45 land classes available in CLC were aggregated to form the following 4 main categories : ( i ) continuous urban fabricroad and rail networks and associated land -port areas ( LC1 ) ; ( ii ) discontinuous urban fabric -industrial or commercial units -mine , dump and construction sites -artificial , non - agricultural vegetated areas ( LC2 ) ; ( iii ) agricultural areas -wetlands -water bodies ( LC3 ) ; and ( iv ) forest and semi natural areas ( LC4 ) . Additionally , the high resolution layers of tree cover density ( TCD , 2015 ) , imperviousness density ( IMP , 2015 ) and European settlement map ( ESM , 2016 ) were accessed from the same source ( CLMS , 2020 ) . The digital elevation model ( Digital Elevation Model Over Europe ( EU - DEM ) , 2017 ) product was downloaded from the EEA website .