Study on the Reconstructing the NO2 Gas Distribution in a Vertical Plane Using MAX-DOAS
CHANG Zhen1, ZHONG Ming-yu2*, SU Jing-ming1, 2, SI Fu-qi1, WANG Yu3, ZHOU Hai-jin1, DOU Ke1, ZHANG Quan1
1. Key Laboratory of Environmental Optical and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
2. College of Electrical and Information Engineering, Anhui University of Science and Technology, Huainan 232001, China
3. Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China
Abstract：The multi-axis differential absorption spectrometer (MAX-DOAS) combined with computed tomography (CT) reconstruction algorithm can be used to obtain the spatial distribution of the target trace gases. In order to study the feasibility of reconstructing the spatial distribution of NO2 on a vertical cross-section under the condition of background concentration (such as the urban background), a confirmatory experiment was designed under the condition of controllable gas density. The feasibility of using MAX-DOAS to reconstruct the distribution of NO2 in the vertical plane is proved. The JGS1 quartz glass sample cell filled with standard gas was used as the research object, and two MAX-DOAS were used to collect spectral data. Taking the gradient of gas density as a priori information, and using the classical ABOCS algorithm and the Barzilai-Borwein algorithm, the NO2 distribution in the vertical plane is reconstructed. The feasibility of using MAX-DOAS to reconstruct the spatial distribution of NO2 in the vertical plane was verified, and the influence of background density on the reconstruction results was determined. The results show that the NO2 density obtained by the retrieving is very close to that by using the sky as the reference spectrum and the empty sample pool as the reference spectrum. Therefore, the influence of the sample pool container on the experimental results can be neglected in the reconstruction method of NO2 vertical plane distribution. The background density of MAX-DOAS with the urban background was high, especially when the observation angle was low, the background density of NO2 was almost 6×1016 molec·cm-2, the MAX-DOAS, whose background density has no obvious pollution source in the city suburb, is low enough to be ignored. The reconstruction results show that the average molecular number density along the optical path is 3.932 7×1015 molec·cm-2 when the observation angle is 28°, and the density in the lower region of the sample pool is higher than that in the upper region. The reconstructed SCD is in good agreement with the measured SCD. The calculated results show that the peak value of molecular number density is 5.77×1015 molec·cm-2, which is close to the MAX-DOAS retrieving results with the background of the urban suburbs. However, it is not close to the MAX-DOAS retrieving results with the background of the urban areas, especially when the elevation angle is small, whose background density of NO2 is especially obvious, and its reconstructed result is much lower than the measured one. To sum up, background density is an artifact in the reconstructed image, which affects the observation of gas distribution. If the prior information of gas density mutation in and out of the sample pool is added to the reconstruction algorithm, the effect of background density on the reconstruction results can be reduced.
Key words：Differential optical absorption spectrometer;Gas reconstructing;MAX-DOAS;Iterative algorithms; Data fitting
常 振，钟鸣宇，苏静明，司福祺，王 煜，周海金，窦 科，张 泉. MAX-DOAS重建NO2竖直平面分布的方法研究[J]. 光谱学与光谱分析, 2023, 43(08): 2413-2418.
CHANG Zhen, ZHONG Ming-yu, SU Jing-ming, SI Fu-qi, WANG Yu, ZHOU Hai-jin, DOU Ke, ZHANG Quan. Study on the Reconstructing the NO2 Gas Distribution in a Vertical Plane Using MAX-DOAS. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2023, 43(08): 2413-2418.
[1] WANG Yang, LI Ang, XIE Pin-hua, et al(王 杨, 李 昂, 谢品华，等). Acta Physica Sinica(物理学报), 2013, 62(20): 200705.
[2] LIU Hao-ran, HU Qi-hou, TAN Wei, et al(刘浩然, 胡启后, 谈 伟，等). Spectroscopy and Spectral Analysis（光谱学与光谱分析）, 2021, 41(1): 11.
[3] Cheng X H, Ma J Z, Jin J L, et al. Atmospheric Chemistry & Physics, 2020, 20: 10757.
[4] Hartl A, Song B C, Pundt I. Atmospheric Chemistry and Physics, 2006, 6(3): 847.
[5] Frins E, Bobrowski N, Platt U, et al. Appl. Opt., 2006, 45(24): 6227.
[6] Pundt I, Kai U M. Appl. Opt., 2005, 44(23): 4985.
[7] Mettendorf K U, Hartl A, Pundt I. Journal of Environmental Monitoring, 2006, 8: 279.
[8] ZHONG Ming-yu, XI Liang, SI Fu-qi, et al(钟鸣宇, 奚 亮, 司福祺，等). Acta Physica Sinica(物理学报), 2019, 68(16): 164205.
[9] Olaguer E P, Stutz J, Erickson M H, et al. Atmospheric Environment, 2017, 150(2): 220.
[10] Laepple T, Knab V, Mettendorf K U, et al. Atmospheric Chemistry and Physics, 2004, 4(5): 1323.
[11] Frins E, Bobrowski N, Osorio M, et al. Atmospheric Environment, 2014, 98: 347.
[12] Niu Tianye, Zhu Lei. Accelerated Barrier Optimization Compressed Sensing (ABOCS) Reconstruction: Performance Evaluation for Cone-beam CT, 2012 Nuclear Science Symposium & Medical Imaging Conference. IEEE, 2013: 4588(doi: 10.1109/NSSMIC.2012.6551535).
