ALBERT

Description: We present the online calculated Earth's surface trace gas and aerosol emissions and dry deposition in the Modular Earth Submodel System (MESSy) submodel EMDEP as well as the currently applied anthropogenic and natural emissions inventories. These inventories, being read-in by the MESSy submodel OFFLEM, include the industrial, fossil fuel, agricultural and biomass burning emissions considering emission height profiles as a function of the source category based on the EDGAR v3.2 fast track 2000 inventory. Terrestrial and marine emissions of a selection of trace gases and aerosols are calculated online in EMDEP using climate model parameters such as wind speed, temperature and land cover and land use parameters. The online dry deposition calculation includes gases and aerosols, where the default selection for the trace gases for the dry deposition scheme can be easily extended using a commonly applied method based on trace gas solubility and reactivity. In general, the simulated global annual emissions agree with previously reported inventories, although differences exist, partly dependent on the applied model resolution. A high sensitivity of the simulated dry deposition to the applied emission height profiles stresses the importance of a realistic and consistent representation of the spatial and temporal variability in surface exchange processes in Earth system models.

Description: Megacities and other major population centers represent important, concentrated sources of anthropogenic pollutants to the atmosphere, with consequences for both local air quality and for regional and global atmospheric chemistry. The tradeoff between the regional buildup of pollutants near their sources versus long-range export depends on meteorological characteristics which vary as a function of geographical location and season. Both horizontal and vertical transport contribute to pollutant export, and the overall degree of export is strongly governed by the chemical lifetimes of pollutants. We provide a first quantification of this tradeoff and the main factors influencing it in terms of "regional pollution potentials", metrics based on simulations of artificial, representative tracers using the 3-D global model MATCH (Model of Atmospheric Transport and Chemistry). The tracers have three different lifetimes (1, 10, and 100 days) and are emitted from 36 continental point sources representing the 30 current largest cities around the world plus 6 additional major population centers. Several key features of the export characteristics emerge: 1) long-range near-surface pollutant export is generally strongest in the middle and high latitudes, especially for source locations in Eurasia; 2) on the other hand, pollutant export to the upper troposphere is greatest in the tropics, due to transport by deep convection; 3) not only are there order of magnitude interregional differences, such as between low and high latitudes, but also often substantial intraregional differences, for instance between the sources in western India and Pakistan versus eastern India and Bangladesh; 4) contrary to what one might initially expect, efficient long-range export does not necessarily correspond with a more significant dilution of pollutants near their source, rather the amount of low-level, long-range export (e.g., below 1 km and beyond 1000 km) is well-correlated with exceedences of surface density thresholds on regional scales near the source (e.g., within ~1000 km), implying that pollutant buildup to high densities in the surface layer of the region surrounding the source location is more strongly influenced by vertical than horizontal transport.