Abstract
Gridded emission inventories are essential inputs for chemical
transport models and climate models. Spatial proxies are applied to allocate
emissions from regional totals to spatially resolved grids when the exact
locations of emissions are absent, with additional uncertainties arising due
to the spatial mismatch between the locations of emissions and spatial
proxies. In this study, we investigate the impact of spatial proxies on the
accuracy of gridded emission inventories at different spatial resolutions by
comparing gridded emissions developed from different spatial proxies
(proxy-based inventory) with a highly spatially disaggregated bottom-up
emission inventory developed from the extensive use of locations of emitting
facilities (bottom-up inventory) in Hebei Province, China. We find that
proxy-based inventories are generally comparable to bottom-up inventories for
grid sizes larger than 0.25° because spatial errors are largely
diminished at coarse resolutions. However, for gridded emissions with finer
resolutions, large positive biases in urban centers and negative biases in
suburban and rural regions are identified in proxy-based inventories and are
then propagated into significant biases in urban-scale chemical transport
modeling. Compared to bottom-up inventories, the use of proxy-based emissions
exhibits similar modeling results, with biases varying from 3 to 13 %
when predicting surface concentrations of different pollutants at 36 km resolution
and an additional 8–73 % at 4 km resolution. The resolution dependence of
uncertainties in proxy-based gridded inventories can be explained by the
decoupling of emission facility locations from spatial surrogates, especially
because industry facilities tend to be located away from urban centers. This
distance results in a divergence between emission distributions and the
allocation of proxies on smaller grids. The decoupling effects are weakened
when the grid size increases to cover both urban and rural regions. We
conclude that proxy-based inventories are of sufficient quality to support
regional and global models (larger than 0.25° in this case study);
however, to support urban-scale models with accurate emission inputs,
bottom-up inventories incorporating the exact locations of emitting
facilities should be developed instead of proxy-based inventories.
Citation
ID:
250829
Ref Key:
zheng2017atmosphericresolution