Downscaling atmospheric emission inventories with “top–down” approach: the support of the literature in choosing proxy variables

The management and improvement of air quality are global challenges aimed at protecting human health and environmental resources. For this purpose, in addition to legislative and scientific indications, numerous tools are available: measurement methods and tools for estimating and forecasting. As a collection of data presenting an emission of a pollutant (to air), emission inventories support the knowledge of sources impacting air quality by estimating atmospheric emissions within a specific (wide or limited) reference area. There are several methodological approaches for their definition, which can be classified into bottom–up or top–down methods. This paper aims to review the methodological approaches described in the literature that apply the top–down approach for the disaggregation of atmospheric emissions with high spatial and temporal resolution. The proxy variables used to apply this approach are identified, as well as the spatial and temporal resolution obtained by the authors. The results show that population density and land use are the most common parameters with respect to most of the emission sources and for numerous atmospheric pollutants. The spatial resolution of the disaggregation described in the literature varies from a few hundred metres to several kilometres, in relation to the territorial extension of the study areas. The results of the review help support the selection of the best and most popular proxy variables used to scale emissions inventories.