Mobile differential optical absorption spectroscopy (mobile DOAS) has become an important tool for the quantification of emission sources, including point sources (e.g., individual power plants) and area emitters (e.g., entire cities). In this study, we focused on the error budget of mobile DOAS measurements from point sources, and we also offered recommendations for the optimum settings of such measurements via a simulation with a modified Gaussian plume model. Following the analysis, we conclude that (1) the proper sampling resolution should be between 5 and 50 m. (2) When measuring far from the source, undetectable flux (measured slant column densities (SCDs) are under the detection limit) resulting from wind dispersion is the main error source. The threshold for the undetectable flux can be lowered by larger integration time. When measuring close to the source, low sampling frequency results in large errors, and wind field uncertainty becomes the main error source of SO₂ flux (for NO_x this error also increases, but other error sources dominate). More measurement times can lower the flux error that results from wind field uncertainty. The proper wind speed for mobile DOAS measurements is between 1 and 4 m s⁻¹. (3) The remaining errors by [NO_x] ∕ [NO₂] ratio correction can be significant when measuring very close. To minimize the [NO_x] ∕ [NO₂] ratio correction error, we recommend minimum distances from the source, at which 5 % of the NO₂ maximum reaction rate is reached and thus NO_x steady state can be assumed. (4) Our study suggests that emission rates < 30 g s⁻¹ for NO_x and < 50 g s⁻¹ for SO₂ are not recommended for mobile DOAS measurements. Based on the model simulations, our study indicates that mobile DOAS measurements are a very well-suited tool to quantify point source emissions. The results of our sensitivity studies are important to make optimum use of such measurements.

中文翻译：

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基于高斯色散模型的移动差分吸收光谱法对NO _x和SO ₂点源发射通量误差的量化：模拟研究

移动差分光吸收光谱法（移动DOAS）已经成为量化排放源的重要工具，包括点源（例如，单个发电厂）和区域排放源（例如，整个城市）。在这项研究中，我们重点研究了来自点源的移动DOAS测量的误差预算，并且还通过改进的高斯羽流模型进行仿真，为此类测量的最佳设置提供了建议。经过分析，我们得出结论：（1）适当的采样分辨率应在5至50 m之间。（2）在远离源的位置进行测量时，主要的误差源是由于风的扩散而导致无法检测到的通量（测得的斜柱密度（SCD）在检测极限以下）。较大的积分时间可以降低无法检测到的通量的阈值。₂通量（对于NO _x，此误差也会增加，但其他误差来源占主导）。更多的测量时间可以降低由风场不确定性导致的磁通误差。用于移动DOAS测量的适当风速在1到4 m s ^-1之间。（3）当非常接近测量时，通过[NO _x ]  ∕  [NO ₂ ]比校正的剩余误差可能会很大。为了最大程度地减少[NO _x ]  ∕  [NO ₂ ]比校正误差，我们建议与源的最小距离，达到NO ₂最大反应速率的5％时，NO _x可以假定为稳态。（4）我们的研究表明，不建议在移动DOAS测量中将NO _x的排放速率<  30 g s ^-1和SO _2的<  50 g s ^-1推荐。基于模型仿真，我们的研究表明，移动DOAS测量是一种非常适合量化点源排放的工具。我们的敏感性研究结果对于最佳利用此类测量非常重要。