Accounting for Small-scale Emission and Concentration Variability in Air Quality Models

Urban and con-urban environments are characterized by heterogeneous emission that do not reflect in emission inventories if not as an average value and are not accounted for in meso- to limited area air quality model. The emissions are averaged over the grid cell where the emission source is located. The source can be linear (e.g. roads), surface (fields or urban areas) or punctual (factory) but after the averaging procedure, it is considered as a surface source with the same extension as the grid cell. This means that not only surface heterogeneity is lost in terms of its level of variability but also it will not be accounted for in the upper atmospheric levels and the impact of spatial distribution of emissions on spatial distribution of concentration is lost. This can represent a serious issue in case of passive as well as chemically reactive species or for the estimation of long or short term exposures. In this paper, we propose a novel approach to the problem including a formulation for the sub-grid variability of pollutant concentrations that takes into account the spatial heterogeneity of the emissions. The formulation that can be used in mesoscale models relies on the resolution of a prognostic equation for the sub-grid concentration variance, i.e. the quantity that accounts for the distribution of concentration within a grid-cell of a mesoscale model, by using a one-and-a-half order closure. The parameterization is implemented in a 1D column model and tested against large eddy simulations of convective atmospheric boundary layers.

GALMARINI Stefano;  VINUESA Jean;  MARTILLI Alberto; 

2009-11-05

University of Cyprus

JRC36542

https://publications.jrc.ec.europa.eu/repository/handle/JRC36542,