你有被称为排放通量的数据。如果这些数据是可用的全球平均然后可以计算全球平均浓度乘以该物种的停留时间与排放通量。然而,在城市或网格层面,它不是简单的计算浓度的排放通量。为了计算,浓度,需要信息分散在三维空间的速度以及物种所带来的风。色散一般估计使用大气传输模型。看到例如Gadhavi et al。(2015)估计浓度排放通量的黑碳粒子。技术上来说,一个可以计算浓度,首先划分区域三维grid-boxes所需的浓度,通过计算每个接口的质量通量grid-boxes以及化学转换盒内。化学转换等物种PM10和PM2.5可能不重要但它可以显著的二氧化硫等物种。质量流量的计算需要知识风速度在接口、扩散混合和框内湍流混合以及去除过程,如干沉积和湿沉积。在这里,一个令人困惑的问题是grid-boxes的大小。 A different size may lead to a different concentration number. Though, there is no hard and fast rule about size of grid-boxes, the decision often depends on resolution of available flux and meteorological data as well as end purpose. Suppose, one is looking for comparing satellite based columnar concentration, he/she may take grid-box height that covers entire atmosphere but if one is planning to compare a surface mass concentration measurement typically obtained by air pollution monitoring stations, vertical height of grid-box should be as small as possible preferably less than boundary layer height. Most emission flux data or emission inventories are available for the emission near Earth's surface. They should be considered as emission flux across the bottom face of the lowest grid-box. The grid box that one but the lowest grid-box will have emission fluxes from top of the lowest grid-box dictated by meteorology and dispersion physics. And the gain of this grid-box will be losses (or negative flux) of the lowest grid box. Besides, losing mass to above, the lowest grid-boxes will also loose mass through process called dry deposition. If the grid-boxes covers the region with rain, then all the grid-boxes from cloud level to surface will also have wet deposition or wet removal. Same applies to mass fluxes in horizontal direction. The lowest grid-box gains mass from bottom face because of emissions but looses to neighboring boxes by horizontal wind. A balance between mass fluxes across all the faces will be concentration of given grid-box. A crude estimation of surface concentration can be obtained by making a certain assumptions, like by taking grid-box height equal to mixing layer height and assuming horizontally uniform emission fluxes across large region. Under this assumptions one can calculate concentration by multiplying emission fluxes with characteristic time period say 24 hour and dividing it by volume of grid-box. The scientific rational behind this assumption is that mixing height is the height of the atmosphere were turbulence is very high and the loss process becomes dominant only after this volume is filled. Also, when the emission region is sufficiently large, horizontal movement of mass will cancel out across opposing face of the grid-box. Reference --------- Gadhavi, H. S., Renuka, K., Ravi Kiran, V., Jayaraman, A., Stohl, A., Klimont, Z., and Beig, G.: Evaluation of black carbon emission inventories using a Lagrangian dispersion model – a case study over southern India, Atmos. Chem. Phys., 15, 1447–1461, https://doi.org/10.5194/acp-15-1447-2015, 2015. Chapter 2 Atmospheric Trace Constituents in Atmospheric Chemistry and Physics by Seinfeld and Pandis, 2006.