Eddy Covariance measurements and source partitioning of CO2 emissions in an urban environment: Application for Heraklion, Greece

Cities are now becoming the focus for CO 2 emission reduction efforts worldwide and there is a growing need for establishing emission inventories , developing methodologies for improved CO 2 monitoring and understanding of the multiple source, sink and storage processes inside the complex urban environment. This study combines Eddy Covariance (EC) measurements of CO 2 flux ( F C ) during one year period over the city centre of Heraklion with analytical morphological and land cover data to achieve a thorough investigation of the spatiotemporal variability and the controlling factors of F C in the urban setting. The detailed characterization of the urban land cover and 3D structure was performed using high resolution Earth Observation data. The urban morphological data was used to parameterize a turbulent flux source area model and the land cover data used to analyse the contribution of the source area components to the measured F C . Heraklion F C does not present any specific seasonal trend according to the meteorological or vegetation changes throughout the year. Heraklion centre behaves as a net emitter diurnally and throughout the year. The diurnal variability presents a standard pattern in weekdays with a major peak in midday and a secondary in afternoon, clearly following the traffic rush-hour peaks. Space heating emissions during winter remain low, hardly affecting the seasonal and diurnal F C patterns. The main CO 2 sources are the major roads and the intersections , where the heavy traffic is located. The source area analysis revealed that traffic contributes 69% to the estimated annual CO 2 emissions. Space heating contributes only 11.6%, while human metabolism is estimated to contribute 19.4%. Vegetation cover of the source area is very low and was assumed to have minor effect to the annual F C budget. The estimated total annual emissions of Heraklion case study reach 19.4 kg CO 2 m −2 y −1 .