A benchmarking tool to screen and compare bottom-up and top-down atmospheric emission inventories

This paper describes the Δ-Emis tool for emission inventories, recently developed in the framework of Forum for Air Quality Modelling in Europe (FAIRMODE). The Δ-Emis tool consists of a set of indicators and diagrams that support the comparison of bottom-up and top-down emission inventories. Four different comparison methods are proposed: (1) pollutant emission comparisons across sectors (bar plot), (2) quantification of the differences between inventories allocated in terms of activity data and emission factors (diamond diagram), (3) emission per capita comparisons (per-capita diagram) and (4) comparison of pollutant ratios (pollutant ratio diagram). The methodology has been tested for an urban emission inventory in Barcelona, and results show the capability of the system to flag inconsistencies in the existing inventories. The strengths and limitations of the tool are presented. The proposed methodology may be useful for regional and urban inventory developers as an initial evaluation of the consistency of their inventories.