ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-13-1547-2013 Tropospheric NO<sub>2</sub> vertical column densities over Beijing: results of the first three years of ground-based MAX-DOAS measurements (2008&ndash;2011) and satellite validation Ma J. Z. 1 Beirle S. 2 Jin J. L. 1 3 Shaiganfar R. 2 Yan P. 1 3 Wagner T. 2 Chinese Academy of Meteorological Sciences, Beijing, China Max Planck Institute for Chemistry, Mainz, Germany now at: CMA Meteorological Observation Centre, Beijing, China 07 02 2013 13 3 1547 1567 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/13/1547/2013/acp-13-1547-2013.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/13/1547/2013/acp-13-1547-2013.pdf

Ground-based measurements of scattered sunlight by the Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) have been carried out at an urban site (39.95° N, 116.32° E) in Beijing megacity since 6 August 2008. In this study, we retrieved the tropospheric NO<sub>2</sub> vertical column densities (VCDs) over Beijing from these MAX-DOAS observations from August 2008 to September 2011. Over this period, the daytime (08:00–17:00 Beijing Time (BJT, which equals UTC + 8)) mean tropospheric NO<sub>2</sub> VCDs varied from 0.5 to 13.3 with an average of 3.6 during summertime, and from 0.2 to 16.8 with an average of 5.8 during wintertime, all in units of 10<sup>16</sup> molecules cm<sup>−2</sup>. The average diurnal variation patterns of tropospheric NO<sub>2</sub> over Beijing appeared to be rather different from one season to another, indicating differences in the emission strength and atmospheric lifetime. In contrast to previous studies, we find a small weekly cycle of the tropospheric NO<sub>2</sub> VCD over Beijing. The NO<sub>2</sub> VCD in the late afternoon was the largest on Saturday and the lowest on Sunday, and in the morning it reached a clear maximum on Wednesday. We also find a post-Olympic Games effect, with 39–54% decrease in the tropospheric NO<sub>2</sub> VCD over Beijing estimated for August of 2008, compared to the following years. The tropospheric NO<sub>2</sub> VCDs derived by our ground MAX-DOAS measurements show a good correlation with SCIAMACHY and OMI satellite data. However, compared with the MAX-DOAS measurements, the satellite observations underestimate the tropospheric NO<sub>2</sub> VCDs over Beijing systematically, by 43% for SCIAMACHY and 26–38% for OMI (DOMINO v2.0 and DOMINO v1.02). Based on radiative transfer simulations, we show that the aerosol shielding effect can explain this underestimation, while the gradient smoothing effect caused by the coarse spatial resolution of the satellite observations could play an additional role.

 References Beirle, S. and Wagner, T.: Tropospheric vertical column densities of NO<sub>2</sub> from SCIAMACHY, available at: http://www.sciamachy.org/products/NO2/NO2vc_v0_9_MPI_AD.pdf (last access: October 2012), 2010. Beirle, S., Platt, U., Wenig, M., and Wagner, T.: Weekly cycle of NO<sub>2</sub> by GOME measurements: a signature of anthropogenic sources, Atmos. Chem. Phys., 3, 2225–2232, http://dx.doi.org/10.5194/acp-3-2225-2003doi:10.5194/acp-3-2225-2003, 2003. Beirle, S., Kühl, S., Pukite, J., and Wagner, T.: Retrieval of tropospheric column densities of NO<sub>2</sub> from combined SCIAMACHY nadir/limb measurements, Atmos. Meas. Tech., 3, 283–299, http://dx.doi.org/10.5194/amt-3-283-2010doi:10.5194/amt-3-283-2010, 2010. Boersma, K. F., Eskes, H. J., and Brinksma, E. J.: Error analysis for tropospheric NO<sub>2</sub> retrieval from space, J. Geophys. Res., 109, D04311, http://dx.doi.org/10.1029/2003jd003962doi:10.1029/2003jd003962, 2004. Boersma, K. F., Eskes, H. J., Veefkind, J. P., Brinksma, E. J., van der A, R. J., Sneep, M., van den Oord, G. H. J., Levelt, P. F., Stammes, P., Gleason, J. F., and Bucsela, E. J.: Near-real time retrieval of tropospheric NO<sub>2</sub> from OMI, Atmos. Chem. Phys., 7, 2103–2118, http://dx.doi.org/10.5194/acp-7-2103-2007doi:10.5194/acp-7-2103-2007, 2007. Boersma, K. F., Eskes, H. J., Dirksen, R. J., van der A, R. J., Veefkind, J. P., Stammes, P., Huijnen, V., Kleipool, Q. L., Sneep, M., Claas, J., Leitão, J., Richter, A., Zhou, Y., and Brunner, D.: An improved tropospheric NO<sub>2</sub> column retrieval algorithm for the Ozone Monitoring Instrument, Atmos. Meas. Tech., 4, 1905–1928, http://dx.doi.org/10.5194/amt-4-1905-2011doi:10.5194/amt-4-1905-2011, 2011. Bovensmann, H., Burrows, J. P., Buchwitz, M., Frerick, J., No\"el, S., Rozanov, V. V., Chance, K. V., and Goede, A. P. H.: SCIAMACHY: Mission objectives and measurement modes, J. Atmos. Sci., 56, 127–150, 1999. Brinksma, E. J., Pinardi, G., Volten, H., Braak, R., Richter, A., Schönhardt, A., van Roozendael, M., Fayt, C., Hermans, C., Dirksen, R. J., Vlemmix, T., Berkhout, A. J. C., Swart, D. P. J., Oetjen, H., Wittrock, F., Wagner, T., Ibrahim, O. W., de Leeuw, G., Moerman, M., Curier, R. L., Celarier, E. A., Cede, A., Knap, W. H., Veefkind, J. P., Eskes, H. J., Allaart, M., Rothe, R., Piters, A. J. M., and Levelt, P. F.: The 2005 and 2006 DANDELIONS NO<sub>2</sub> and aerosol intercomparison campaigns, J. Geophys. Res., 113, D16S46, http://dx.doi.org/10.1029/2007jd008808doi:10.1029/2007jd008808, 2008. Burrows, J. P., Richter, A., Dehn, A., Deters, B., Himmelmann, S., Voigt, S., and Orphal, J.: Atmospheric remote sensing reference data from GOME-2. temperature-dependent absorption cross-sections of O<sub>3</sub> in the 231–794 nm range, J. Quant. Spectrosc. Ra., 61, 509–517, 1999a. Burrows, J. P., Weber, M., Buchwitz, M., Rozanov, V. V., Ladstätter-Weißenmayer, A., Richter, A., DeBeek, R., Hoogen, R., Brmstedt, K., and Eichmann, K. U.: The global ozone monitoring experiment (GOME): mission concept and first scientific results, J. Atmos. Sci., 56, 151–175, 1999b. Celarier, E. A., Brinksma, E. J., Gleason, J. F., Veefkind, J. P., Cede, A., Herman, J. R., Ionov, D., Goutail, F., Pommereau, J. P., Lambert, J. C., van Roozendael, M., Pinardi, G., Wittrock, F., Schönhardt, A., Richter, A., Ibrahim, O. W., Wagner, T., Bojkov, B., Mount, G., Spinei, E., Chen, C. M., Pongetti, T. J., Sander, S. P., Bucsela, E. J., Wenig, M. O., Swart, D. P. J., Volten, H., Kroon, M., and Levelt, P. F.: Validation of Ozone Monitoring Instrument nitrogen dioxide columns, J. Geophys. Res., 113, D15S15, http://dx.doi.org/10.1029/2007jd008908doi:10.1029/2007jd008908, 2008. Chen, D., Zhou, B., Beirle, S., Chen, L. M., and Wagner, T.: Tropospheric NO<sub>2</sub> column densities deduced from zenith-sky DOAS measurements in Shanghai, China, and their application to satellite validation, Atmos. Chem. Phys., 9, 3641–3662, http://dx.doi.org/10.5194/acp-9-3641-2009doi:10.5194/acp-9-3641-2009, 2009. Chou, C. C.-K., Tsai, C.-Y., Chang, C.-C., Lin, P.-H., Liu, S. C., and Zhu, T.: Photochemical production of ozone in Beijing during the 2008 Olympic Games, Atmos. Chem. Phys., 11, 9825–9837, http://dx.doi.org/10.5194/acp-11-9825-2011doi:10.5194/acp-11-9825-2011, 2011. Cinzano, P., Falchi, F., and Elvidge, C. D.: The first world atlas of the artificial night sky brightness, Mon. Not. R. Astron. Soc., 328, 689–707, 2001. Clémer, K., Van Roozendael, M., Fayt, C., Hendrick, F., Hermans, C., Pinardi, G., Spurr, R., Wang, P., and De Mazière, M.: Multiple wavelength retrieval of tropospheric aerosol optical properties from MAXDOAS measurements in Beijing, Atmos. Meas. Tech., 3, 863–878, http://dx.doi.org/10.5194/amt-3-863-2010doi:10.5194/amt-3-863-2010, 2010. Deutschmann, T.: Atmospheric radiative transfer modelling using Monte Carlo methods, Diploma Thesis, University of Heidelberg, Heidelberg, Germany, 2009. Deutschmann, T., Beirle, S., Frieß, U., Grzegorski, M., Kern, C., Kritten, L., Platt, U., Prados-Román, C., Pu\=ite, J., Wagner, T., Werner, B., and Pfeilsticker, K.: The Monte Carlo atmospheric radiative transfer model McArtim: Introduction and validation of Jacobians and 3D features, J. Quant. Spectrosc. Ra., 112, 1119–1137, 2011. EPA: Air Quality Index-A Guide to Air Quality and Your Health, United States Environmental Protection Agency, Washington, DC20460, EPA-454/R-00-005, 2000. Fayt, C. and Van Roozendael, M.: WinDOAS 2.1 software user manual, IASB/BIRA Uccle, Belgium, 2001. Garland, R. M., Schmid, O., Nowak, A., Achtert, P., Wiedensohler, A., Gunthe, S. S., Takegawa, N., Kita, K., Kondo, Y., Hu, M., Shao, M., Zeng, L. M., Zhu, T., Andreae, M. O., and Pöschl, U.: Aerosol optical properties observed during Campaign of Air Quality Research in Beijing 2006 (CAREBeijing-2006): Characteristic differences between the inflow and outflow of Beijing city air, J. Geophys. Res., 114, D00G04, http://dx.doi.org/10.1029/2008jd010780doi:10.1029/2008jd010780, 2009. Greenblatt, G. D., Orlando, J. J., Burkholder, J. B., and Ravishankara, A. R.: Absorption measurements of oxygen between 330 and 1140 nm, J. Geophys. Res., 95, 18577–18582, http://dx.doi.org/10.1029/JD095iD11p18577doi:10.1029/JD095iD11p18577, 1990. Hönninger, G., von Friedeburg, C., and Platt, U.: Multi axis differential optical absorption spectroscopy (MAX-DOAS), Atmos. Chem. Phys., 4, 231–254, http://dx.doi.org/10.5194/acp-4-231-2004doi:10.5194/acp-4-231-2004, 2004. Hains, J. C., Boersma, K. F., Kroon, M., Dirksen, R. J., Cohen, R. C., Perring, A. E., Bucsela, E., Volten, H., Swart, D. P. J., Richter, A., Wittrock, F., Schoenhardt, A., Wagner, T., Ibrahim, O. W., van Roozendael, M., Pinardi, G., Gleason, J. F., Veefkind, J. P., and Levelt, P.: Testing and improving OMI DOMINO tropospheric NO<sub>2</sub> using observations from the DANDELIONS and INTEX-B validation campaigns, J. Geophys. Res., 115, D05301, http://dx.doi.org/10.1029/2009jd012399doi:10.1029/2009jd012399, 2010. Hayn, M., Beirle, S., Hamprecht, F. A., Platt, U., Menze, B. H., and Wagner, T.: Analysing spatio-temporal patterns of the global NO<sub>2</sub>-distribution retrieved from GOME satellite observations using a generalized additive model, Atmos. Chem. Phys., 9, 6459–6477, http://dx.doi.org/10.5194/acp-9-6459-2009doi:10.5194/acp-9-6459-2009, 2009. He, X., Li, C. C., Lau, A. K. H., Deng, Z. Z., Mao, J. T., Wang, M. H., and Liu, X. Y.: An intensive study of aerosol optical properties in Beijing urban area, Atmos. Chem. Phys., 9, 8903–8915, http://dx.doi.org/10.5194/acp-9-8903-2009doi:10.5194/acp-9-8903-2009, 2009. Ibrahim, O., Shaiganfar, R., Sinreich, R., Stein, T., Platt, U., and Wagner, T.: Car MAX-DOAS measurements around entire cities: quantification of NO$_\textx$ emissions from the cities of Mannheim and Ludwigshafen (Germany), Atmos. Meas. Tech., 3, 709–721, http://dx.doi.org/10.5194/amt-3-709-2010doi:10.5194/amt-3-709-2010, 2010. Irie, H., Kanaya, Y., Akimoto, H., Tanimoto, H., Wang, Z., Gleason, J. F., and Bucsela, E. J.: Validation of OMI tropospheric NO<sub>2</sub> column data using MAX-DOAS measurements deep inside the North China Plain in June 2006: Mount Tai Experiment 2006, Atmos. Chem. Phys., 8, 6577–6586, http://dx.doi.org/10.5194/acp-8-6577-2008doi:10.5194/acp-8-6577-2008, 2008. Jiang, W. H., Ma, J. Z., Yan, P., Richter, A., Burrows, J. P., and Nüß, H.: Characterization of NO<sub>2</sub> pollution changes in Beijing using GOME satellite data, J. Appl. Meteor. Sci, 17, 67–72, 2006. Jin, X., Xie, P. H., Si, F. Q., Dou, K., Li, A., Liu, Y., and Liu, W. Q.: Retrieval of tropospheric NO<sub>2</sub> by Multi Axis Differential Optical Absorption Spectroscopy, Spectrosc. Spect. Anal., 30, 2464–2469, 2010. Kramer, L. J., Leigh, R. J., Remedios, J. J., and Monks, P. S.: Comparison of OMI and ground-based in situ and MAX-DOAS measurements of tropospheric nitrogen dioxide in an urban area, J. Geophys. Res., 113, D16S39, http://dx.doi.org/10.1029/2007jd009168doi:10.1029/2007jd009168, 2008. Kraus, S.: DOASIS, DOAS for Windows software [CD-ROM], in: Proceedings of the 1st International DOAS-Workshop, Heidelberg, Germany, 13–14 September 2001, 2001. Leitão, J., Richter, A., Vrekoussis, M., Kokhanovsky, A., Zhang, Q. J., Beekmann, M., and Burrows, J. P.: On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors, Atmos. Meas. Tech., 3, 475–493, http://dx.doi.org/10.5194/amt-3-475-2010doi:10.5194/amt-3-475-2010, 2010. Lelieveld, J. and Dentener, F. J.: What controls tropospheric ozone?, J. Geophys. Res., 105, 3531–3551, http://dx.doi.org/10.1029/1999jd901011doi:10.1029/1999jd901011, 2000. Lelieveld, J., Peters, W., Dentener, F. J., and Krol, M. C.: Stability of tropospheric hydroxyl chemistry, J. Geophys. Res., 107, 4715, http://dx.doi.org/10.1029/2002jd002272doi:10.1029/2002jd002272, 2002. Levelt, P., Van den Oord, G., Dobber, M., Malkki, A., Visser, H., de Vries, J., Stammes, P., Lundell, J., and Saari, H.: The Ozone Monitoring Instrument, IEEE T. Geosci. Remote, 44, 1093–1101, http://dx.doi.org/10.1109/TGRS.2006.872333doi:10.1109/TGRS.2006.872333, 2006. Li, X., Brauers, T., Hofzumahaus, A., Lu, K., Li, Y. P., Shao, M., Wagner, T., and Wahner, A.: MAX-DOAS measurements of NO<sub>2</sub>, HCHO and CHOCHO at a rural site in Southern China, Atmos. Chem. Phys. Discuss., 12, 3983–4029, http://dx.doi.org/10.5194/acpd-12-3983-2012doi:10.5194/acpd-12-3983-2012, 2012. Lin, J.-T.: Satellite constraint for emissions of nitrogen oxides from anthropogenic, lightning and soil sources over East China on a high-resolution grid, Atmos. Chem. Phys., 12, 2881–2898, http://dx.doi.org/10.5194/acp-12-2881-2012doi:10.5194/acp-12-2881-2012, 2012. Lin, J.-T. and McElroy, M. B.: Detection from space of a reduction in anthropogenic emissions of nitrogen oxides during the Chinese economic downturn, Atmos. Chem. Phys., 11, 8171–8188, http://dx.doi.org/10.5194/acp-11-8171-2011doi:10.5194/acp-11-8171-2011, 2011. Lin, J.-T., McElroy, M. B., and Boersma, K. F.: Constraint of anthropogenic NO$_\textx$ emissions in China from different sectors: a new methodology using multiple satellite retrievals, Atmos. Chem. Phys., 10, 63–78, http://dx.doi.org/10.5194/acp-10-63-2010doi:10.5194/acp-10-63-2010, 2010. Lin, W., Xu, X., Ge, B., and Liu, X.: Gaseous pollutants in Beijing urban area during the heating period 2007–2008: variability, sources, meteorological, and chemical impacts, Atmos. Chem. Phys., 11, 8157–8170, http://dx.doi.org/10.5194/acp-11-8157-2011doi:10.5194/acp-11-8157-2011, 2011. Lu, K., Zhang, Y., Su, H., Brauers, T., Chou, C. C., Hofzumahaus, A., Liu, S. C., Kita, K., Kondo, Y., Shao, M., Wahner, A., Wang, J., Wang, X., and Zhu, T.: Oxidant (O$_3 \quad +$ NO$_2)$ production processes and formation regimes in Beijing, J. Geophys. Res., 115, D07303, http://dx.doi.org/10.1029/2009jd012714doi:10.1029/2009jd012714, 2010. Ma, J., Richter, A., Burrows, J. P., Nüß, H., and van Aardenne, J. A.: Comparison of model-simulated tropospheric NO<sub>2</sub> over China with GOME-satellite data, Atmos. Environ., 40, 593–604, 2006. Ma, J. Z., Wang, W., Chen, Y., Liu, H. J., Yan, P., Ding, G. A., Wang, M. L., Sun, J., and Lelieveld, J.: The IPAC-NC field campaign: a pollution and oxidization pool in the lower atmosphere over Huabei, China, Atmos. Chem. Phys., 12, 3883–3908, http://dx.doi.org/10.5194/acp-12-3883-2012doi:10.5194/acp-12-3883-2012, 2012. Martin, R. V., Jacob, D. J., Chance, K., Kurosu, T. P., Palmer, P. I., and Evans, M. J.: Global inventory of nitrogen oxide emissions constrained by space-based observations of NO<sub>2</sub> columns, J. Geophys. Res., 108, 4537, http://dx.doi.org/10.1029/2003jd003453doi:10.1029/2003jd003453, 2003. Mijling, B., van der A, R. J., Boersma, K. F., Van Roozendael, M., De Smedt, I., and Kelder, H. M.: Reductions of NO<sub>2</sub> detected from space during the 2008 Beijing Olympic Games, Geophys. Res. Lett., 36, L13801, http://dx.doi.org/10.1029/2009gl038943doi:10.1029/2009gl038943, 2009. Molina, M. J. and Molina, L. T.: Megacities and atmospheric pollution, J. Air Waste Manage. Assoc. , 54, 644–680, 2004. Parrish, D. D. and Zhu, T.: Clean Air for Megacities, Science, 326, 674–675, http://dx.doi.org/10.1126/science.1176064doi:10.1126/science.1176064, 2009. Piters, A. J. M., Boersma, K. F., Kroon, M., Hains, J. C., Van Roozendael, M., Wittrock, F., Abuhassan, N., Adams, C., Akrami, M., Allaart, M. A. F., Apituley, A., Beirle, S., Bergwerff, J. B., Berkhout, A. J. C., Brunner, D., Cede, A., Chong, J., Clémer, K., Fayt, C., Frieß, U., Gast, L. F. L., Gil-Ojeda, M., Goutail, F., Graves, R., Griesfeller, A., Großmann, K., Hemerijckx, G., Hendrick, F., Henzing, B., Herman, J., Hermans, C., Hoexum, M., van der Hoff, G. R., Irie, H., Johnston, P. V., Kanaya, Y., Kim, Y. J., Klein Baltink, H., Kreher, K., de Leeuw, G., Leigh, R., Merlaud, A., Moerman, M. M., Monks, P. S., Mount, G. H., Navarro-Comas, M., Oetjen, H., Pazmino, A., Perez-Camacho, M., Peters, E., du Piesanie, A., Pinardi, G., Puentedura, O., Richter, A., Roscoe, H. K., Schönhardt, A., Schwarzenbach, B., Shaiganfar, R., Sluis, W., Spinei, E., Stolk, A. P., Strong, K., Swart, D. P. J., Takashima, H., Vlemmix, T., Vrekoussis, M., Wagner, T., Whyte, C., Wilson, K. M., Yela, M., Yilmaz, S., Zieger, P., and Zhou, Y.: The Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI): design, execution, and early results, Atmos. Meas. Tech., 5, 457–485, http://dx.doi.org/10.5194/amt-5-457-2012doi:10.5194/amt-5-457-2012, 2012. Platt, U.: Differential optical absorption spectroscopy (DOAS), in: Air Monitoring by Spectroscopic Techniques, edited by: Sigrist, M. W., Chemical Analysis Series, 127, John Wiley, New York, 27–84, 1994. Platt, U. and Stutz, J.: Differential Optical Absorption Spectroscopy Principles and Applications, Series: Physics of Earth and Space Environments, Springer, Heidelberg, 597 pp., 2008. Richter, A., Burrows, J. P., Nusz, H., Granier, C., and Niemeier, U.: Increase in tropospheric nitrogen dioxide over China observed from space, Nature, 437, 129–132, http://dx.doi.org/10.1038/nature04092doi:10.1038/nature04092, 2005. Richter, A., Wittrock, F., Heckel, A., and Burrows, J. P.: Monitoring Changes in Tropospheric Constitution from Space, annual report to ACCENT-TROPOSAT-2 (AT2), Task Group 1, available at: http://www.doas-bremen.de/reports/accent_richter_report_4thyear.pdf (last access: October 2012), 2008. Richter, A., Begoin, M., Hilboll, A., and Burrows, J. P.: An improved NO<sub>2</sub> retrieval for the GOME-2 satellite instrument, Atmos. Meas. Tech., 4, 1147–1159, http://dx.doi.org/10.5194/amt-4-1147-2011doi:10.5194/amt-4-1147-2011, 2011. Sarkissian, A., Pommereau, J., Pierre, Goutail, F., and Kyro, E.: PSC and volcanic aerosol observations during EASOE by UV-visible ground-based spectrometry, Geophys. Res. Lett., 21, 1319–1322, http://dx.doi.org/10.1029/93gl03072doi:10.1029/93gl03072, 1994. Seinfeld, J. H. and Pandis, S. N.: Atmospheric Chemistry and Physics, John Wiley and Sons., New York, 1998. SEPA: Ambient air quality standard, People's Repulic of China National Standard GB 3095-1996, 1996. Shaiganfar, R., Beirle, S., Sharma, M., Chauhan, A., Singh, R. P., and Wagner, T.: Estimation of NO$_\textx$ emissions from Delhi using Car MAX-DOAS observations and comparison with OMI satellite data, Atmos. Chem. Phys., 11, 10871–10887, http://dx.doi.org/10.5194/acp-11-10871-2011doi:10.5194/acp-11-10871-2011, 2011. Shi, C. N., Fernando, H. J. S., Wang, Z. F., An, X. Q., and Wu, Q. Z.: Tropospheric NO<sub>2</sub> columns over East Central China: Comparisons between SCIAMACHY measurements and nested CMAQ simulations, Atmos. Environ., 42, 7165–7173, http://dx.doi.org/10.1016/j.atmosenv.2008.05.046doi:10.1016/j.atmosenv.2008.05.046, 2008. Solomon, S., Portmann, R. W., Sanders, R. W., Daniel, J. S., Madsen, W., Bartram, B., and Dutton, E. G.: On the role of nitrogen dioxide in the absorption of solar radiation, J. Geophys. Res., 104, 12047–12058, http://dx.doi.org/10.1029/1999jd900035doi:10.1029/1999jd900035, 1999. Stone, R.: Beijing's Marathon Run to Clean Foul Air Nears Finish Line, Science, 321, 636–637, http://dx.doi.org/10.1126/science.321.5889.636doi:10.1126/science.321.5889.636, 2008. Sun, J., Zhang, Q., Canagaratna, M. R., Zhang, Y., Ng, N. L., Sun, Y., Jayne, J. T., Zhang, X., Zhang, X., and Worsnop, D. R.: Highly time- and size-resolved characterization of submicron aerosol particles in Beijing using an Aerodyne Aerosol Mass Spectrometer, Atmos. Environ., 44, 131–140, 2010. Tang, G., Li, X., Wang, Y., Xin, J., and Ren, X.: Surface ozone trend details and interpretations in Beijing, 2001–2006, Atmos. Chem. Phys., 9, 8813–8823, http://dx.doi.org/10.5194/acp-9-8813-2009doi:10.5194/acp-9-8813-2009, 2009. Valks, P., Pinardi, G., Richter, A., Lambert, J.-C., Hao, N., Loyola, D., Van Roozendael, M., and Emmadi, S.: Operational total and tropospheric NO<sub>2</sub> column retrieval for GOME-2, Atmos. Meas. Tech., 4, 1491–1514, http://dx.doi.org/10.5194/amt-4-1491-2011doi:10.5194/amt-4-1491-2011, 2011. van der A, R. J., Peters, D. H. M. U., Eskes, H., Boersma, K. F., Van Roozendael, M., De Smedt, I., and Kelder, H. M.: Detection of the trend and seasonal variation in tropospheric NO<sub>2</sub> over China, J. Geophys. Res., 111, D12317, http://dx.doi.org/10.1029/2005jd006594doi:10.1029/2005jd006594, 2006. van der A, R. J., Eskes, H. J., Boersma, K. F., van Noije, T. P. C., Van Roozendael, M., De Smedt, I., Peters, D. H. M. U., and Meijer, E. W.: Trends, seasonal variability and dominant NO$_\textx$ source derived from a ten year record of NO2 measured from space, J. Geophys. Res., 113, D04302, http://dx.doi.org/10.1029/2007jd009021doi:10.1029/2007jd009021, 2008. Vandaele, A. C., Hermans, C., Simon, P. C., Carleer, M., Colin, R., Fally, S., Mérienne, M. F., Jenouvrier, A., and Coquart, B.: Measurements of the NO<sub>2</sub> absorption cross-section from 42 000 cm<sup>−1</sup> to 10 000 cm<sup>−1</sup> (238–1000 nm) at 220 K and 294 K, J. Quant. Spectrosc. Ra., 59, 171–184, 1998. Wagner, T., Dix, B., Friedeburg, C. v., Frieß, U., Sanghavi, S., Sinreich, R., and Platt, U.: MAX-DOAS O<sub>4</sub> measurements: A new technique to derive information on atmospheric aerosols – Principles and information content, J. Geophys. Res., 109, D22205, http://dx.doi.org/10.1029/2004jd004904doi:10.1029/2004jd004904, 2004. Wagner, T., Beirle, S., Deutschmann, T., Eigemeier, E., Frankenberg, C., Grzegorski, M., Liu, C., Marbach, T., Platt, U., and Penning de Vries, M.: Monitoring of atmospheric trace gases, clouds, aerosols and surface properties from UV/vis/NIR satellite instruments, J. Opt. A: Pure Appl. Opt., 10, 104019, http://dx.doi.org/10.1088/1464-4258/10/10/104019doi:10.1088/1464-4258/10/10/104019, 2008. Wagner, T., Deutschmann, T., and Platt, U.: Determination of aerosol properties from MAX-DOAS observations of the Ring effect, Atmos. Meas. Tech., 2, 495–512, http://dx.doi.org/10.5194/amt-2-495-2009doi:10.5194/amt-2-495-2009, 2009. Wagner, T., Ibrahim, O., Shaiganfar, R., and Platt, U.: Mobile MAX-DOAS observations of tropospheric trace gases, Atmos. Meas. Tech., 3, 129–140, http://dx.doi.org/10.5194/amt-3-129-2010doi:10.5194/amt-3-129-2010, 2010. Wang, S. X., Zhao, M., Xing, J., Wu, Y., Zhou, Y., Lei, Y., He, K. B., Fu, L. X., and Hao, J. M.: Quantifying the air pollutants emission reduction during the 2008 Olympic Games in Beijing, Environ. Sci. Technol., 44, 2490–2496, http://dx.doi.org/10.1021/es9028167doi:10.1021/es9028167, 2010a. Wang, T., Nie, W., Gao, J., Xue, L. K., Gao, X. M., Wang, X. F., Qiu, J., Poon, C. N., Meinardi, S., Blake, D., Wang, S. L., Ding, A. J., Chai, F. H., Zhang, Q. Z., and Wang, W. X.: Air quality during the 2008 Beijing Olympics: secondary pollutants and regional impact, Atmos. Chem. Phys., 10, 7603–7615, http://dx.doi.org/10.5194/acp-10-7603-2010doi:10.5194/acp-10-7603-2010, 2010b. Wang, Y., McElroy, M. B., Boersma, K. F., Eskes, H. J., and Veefkind, J. P.: Traffic restrictions associated with the Sino-African summit: Reductions of NO$_\textx$ detected from space, Geophys. Res. Lett., 34, L08814, http://dx.doi.org/10.1029/2007gl029326doi:10.1029/2007gl029326, 2007a. Wang, Y., McElroy, M. B., Martin, R. V., Streets, D. G., Zhang, Q., and Fu, T.-M.: Seasonal variability of NO$_\textx$ emissions over east China constrained by satellite observations: Implications for combustion and microbial sources, J. Geophys. Res., 112, D06301, http://dx.doi.org/10.1029/2006jd007538doi:10.1029/2006jd007538, 2007b. Wang, Y., Che, H., Ma, J., Wang, Q., Shi, G., Chen, H., Goloub, P., and Hao, X.: Aerosol radiative forcing under clear, hazy, foggy, and dusty weather conditions over Beijing, China, Geophys. Res. Lett., 36, L06804, http://dx.doi.org/10.1029/2009gl037181doi:10.1029/2009gl037181, 2009. Witte, J. C., Schoeberl, M. R., Douglass, A. R., Gleason, J. F., Krotkov, N. A., Gille, J. C., Pickering, K. E., and Livesey, N.: Satellite observations of changes in air quality during the 2008 Beijing Olympics and Paralympics, Geophys. Res. Lett., 36, L17803, http://dx.doi.org/10.1029/2009gl039236doi:10.1029/2009gl039236, 2009. Wittrock, F., Oetjen, H., Richter, A., Fietkau, S., Medeke, T., Rozanov, A., and Burrows, J. P.: MAX-DOAS measurements of atmospheric trace gases in Ny-Ålesund – Radiative transfer studies and their application, Atmos. Chem. Phys., 4, 955–966, http://dx.doi.org/10.5194/acp-4-955-2004doi:10.5194/acp-4-955-2004, 2004. Xu, J., Ma, J. Z., Zhang, X. L., Xu, X. B., Xu, X. F., Lin, W. L., Wang, Y., Meng, W., and Ma, Z. Q.: Measurements of ozone and its precursors in Beijing during summertime: impact of urban plumes on ozone pollution in downwind rural areas, Atmos. Chem. Phys., 11, 12241–12252, http://dx.doi.org/10.5194/acp-11-12241-2011doi:10.5194/acp-11-12241-2011, 2011. Yu, H., Wang, P. C., Zong, X. M., Li, X., and Lu, D. R.: Change of NO<sub>2</sub> column density over Beijing from satellite measurement during the Beijing 2008 Olympic Games, Chin. Sci. Bull., 55, 308–313, http://dx.doi.org/10.1007/s11434-009-0375-0doi:10.1007/s11434-009-0375-0, 2010. Zhang, X. Y., Zhang, P., Zhang, Y., Li, X. J., and Qiu, H.: The trend, seasonal cycle, and sources of tropospheric NO<sub>2</sub> over China during 1997-2006 based on satellite measurement, Sci. China Ser. D-Earth Sci., 50, 1877–1884, http://dx.doi.org/10.1007/s11430-007-0141-6doi:10.1007/s11430-007-0141-6, 2007. Zhao, B., Wang, P., Ma, J. Z., Zhu, S., Pozzer, A., and Li, W.: A high-resolution emission inventory of primary pollutants for the Huabei region, China, Atmos. Chem. Phys., 12, 481–501, http://dx.doi.org/10.5194/acp-12-481-2012doi:10.5194/acp-12-481-2012, 2012. Zhao, C. S., Tie, X. X., Wang, G. L., Qin, Y., and Yang, P. C.: Analysis of air quality in eastern China and its interaction with other regions of the world, J. Atmos. Chem., 55, 189–204, http://dx.doi.org/10.1007/s10874-006-9022-1doi:10.1007/s10874-006-9022-1, 2006. Zhu, Y. W., Liu, W. Q., Hua, X. P., Dou, K., Si, F. Q., Li, S. W., Zhang, Y. H., and Qin, M.: Monitoring and analysis of atmospheric pollutants in traffic ban period of Beijing with DOAS, Ac. Photon. Sin., 38, 2040–2045, 2009. Zhu, Y. W., Liu, W. Q., Fang, J., Xie, P. H., Dou, K., Qin, M., and Si, F. Q.: Monitoring and analysis of vertical profile of atmospheric HONO and NO<sub>2</sub> in the boundary layer of Beijing, Spectrosc. Spect. Anal., 31, 1078–1082, 2010.