ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-12475-2011 Determination of tropospheric vertical columns of NO<sub>2</sub> and aerosol optical properties in a rural setting using MAX-DOAS Halla J. D. 1 Wagner T. 2 Beirle S. 2 Brook J. R. 3 Hayden K. L. 3 O'Brien J. M. 3 Ng A. 4 Majonis D. 1 6 Wenig M. O. 5 McLaren R. 1 Centre for Atmospheric Chemistry, York University, Toronto, ON, Canada Satellite Group, Max Planck Institute for Chemistry, Mainz, Germany Air Quality Research Division, Environment Canada, Toronto, ON, Canada Ontario Ministry of the Environment, Toronto, ON, Canada School of Energy and Environment, City U, Hong Kong, China now at: Department of Chemistry, University of Toronto, Toronto, ON, Canada 13 12 2011 11 23 12475 12498 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/11/12475/2011/acp-11-12475-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/12475/2011/acp-11-12475-2011.pdf

Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed in a rural location of southwestern Ontario during the Border Air Quality and Meteorology Study. Slant column densities (SCDs) of NO<sub>2</sub> and O<sub>4</sub> were determined using the standard DOAS technique. Using a radiative transfer model and the O<sub>4</sub> SCDs, aerosol optical depths were determined for clear sky conditions and compared to OMI, MODIS, AERONET, and local PM<sub>2.5</sub> measurements. This aerosol information was input to a radiative transfer model to calculate NO<sub>2</sub> air mass factors, which were fit to the measured NO<sub>2</sub> SCDs to determine tropospheric vertical column densities (VCDs) of NO<sub>2</sub>. The method of determining NO<sub>2</sub> VCDs in this way was validated for the first time by comparison to composite VCDs derived from aircraft and ground-based measurements of NO<sub>2</sub>. The new VCDs were compared to VCDs of NO<sub>2</sub> determined via retrievals from the satellite instruments SCIAMACHY and OMI, for overlapping time periods. The satellite-derived VCDs were higher, with a mean bias of +0.5–0.9×10<sup>15</sup> molec cm<sup>−2</sup>. This last finding is different from previous studies whereby MAX-DOAS geometric VCDs were higher than satellite determinations, albeit for urban areas with higher VCDs. An effective boundary layer height, BLH<sub>eff</sub>, is defined as the ratio of the tropospheric VCD and the ground level concentration of NO<sub>2</sub>. Variations of BLH<sub>eff</sub> can be linked to time of day, source region, stability of the atmosphere, and the presence or absence of elevated NO<sub>x</sub> sources. In particular, a case study is shown where a high VCD and BLH<sub>eff</sub> were observed when an elevated industrial plume of NO<sub>x</sub> and SO<sub>2</sub> was fumigated to the surface as a lake breeze impacted the measurement site. High BLH<sub>eff</sub> values (~1.9 km) were observed during a regional smog event when high winds from the SW and high convection promoted mixing throughout the boundary layer. During this event, the regional line flux of NO<sub>2</sub> through the region was estimated to be greater than 112 kg NO<sub>2</sub> km<sup>−1</sup> h<sup>−1</sup>.

 References Alicke, B., Geyer, A., Hofzumahaus, A., Holland, F., Konrad, S., Patz, H W., Schafer, J., Stutz, J., Volz-Thomas, A., and Platt, U.: OH formation by HONO photolysis during the BERLIOZ experiment, J. Geophys. Res.-Atmos., 108, 8247, http://dx.doi.org/10.1029/2001JD000579doi:10.1029/2001JD000579, 2003. Beirle, S., Kühl, S., Pu\c k\=\ite, 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-3-283-2010,1 2010. Blond, N., Boersma, K F., Eskes, H J., van~der A, R J., Roozendael, M V., Smedt, I D., Bergametti, G., and Vautard, R.: Intercomparison of SCIAMACHY nitrogen dioxide observations, in situ measurements and air quality modeling results over Western Europe, J. Geophys. Res.-Atmos., 112, D10311, http://dx.doi.org/10.1029/2006JD007277doi:10.1029/2006JD007277, 2007. Boersma, K F., Bucsela, E J., Brinksma, E J., and Gleason, J F.: NO<sub>2</sub>, OMI-EOS Algorithm, Theoretical Basis Document: Trace Gas Algorithms: NO<sub>2</sub>, 12–35, 2001. Bogumil, K., Orphal, J., Homann, T., Voigt, S., Spietz, P., Fleischmann, O C., Vogel, A., Hartmann, M., Kromminga, H., Bovensmann, H., Frerick, J., and Burrows, J P.: Measurements of molecular absorption spectra with the SCIAMACHY pre-flight model: instrument characterization and reference data for atmospheric remote-sensing in the 230–2380 nm region, J. Photoch. Photobio. A, 157, 167–184, 2003. Bovensmann, H., Burrows, J P., Buchwitz, M., Frerick, J., Noel, 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., Schoenhardt, 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.-Atmos., 113, D16S46, http://dx.doi.org/10.1029/2007JD008808doi:10.1029/2007JD008808, 2008. Bucsela, E., Celarier, E., Wenig, M., Gleason, J., Veefkind, J., Boersma, K F., and Brinksma, E.: Algorithm for NO<sub>2</sub> vertical column retrieval from the Ozone Monitoring Instrument, IEEE T. Geosci. Remote, 44, 1245–1258, 2006. Burrows, J P., Richter, A., Dehn, A., Deters, B., Himmelmann, 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, 1999. 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., Roozendael, M V., Pinardi, G., Wittrock, F., Schoenhardt, 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.-Atmos., 113, D15S15, http://dx.doi.org/10.1029/2007JD008908doi:10.1029/2007JD008908, 2008. Chance, K V. and Spurr, R. J D.: Ring effect studies: Rayleigh scattering, including molecular parameters for rotational Raman scattering, and the Fraunhofer spectrum, Appl. Optics, 36, 5224–5230, 1997. 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. Chu, D A., Kaufman, Y J., Zibordi, G., Chern, J D., Mao, J., Li, C C., and Holben, B N.: Global monitoring of air pollution over land from the Earth Observing System-Terra Moderate Resolution Imaging Spectroradiometer (MODIS), J. Geophys. Res.-Atmos., 108, 4661, http://dx.doi.org/10.1029/2002JD003179doi:10.1029/2002JD003179, 2003. Clémer, K., Van Roozendael, M., Fayt, C., Hendrick, F., Hermans, C., Pinardi, G., Spurr, R., Wang, P., and De Maziére, 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. Dentener, F J. and Crutzen, P J.: Reaction of N<sub>2</sub>O$_5$ on Tropospheric Aerosols – Impact on the Global Distributions of NO$_\textrmx$, O<sub>3</sub>, and OH, J. Geophys. Res.-Atmos., 98, 7149–7163, 1993. Deutschmann, T., Beirle, S., Frieß, U., Grzegorski, M., Kern, C., Kritten, L., Platt, U., Prados-Román, C., Pu\c k\=\ite, J., Wagner, T., Werner, B., and Pfeilsticker, K.: The Monte carlo Atmospheric radiative transfer model McArtim: Introduction and validation of Jacobians and 3-D features, J. Quant. Spectrosc. Ra., 112, 1119–1137, 2011. Draxler, R R. and Rolph, G D.:HYbrid Single-Particle Lagrangian Integrated Trajectory Model, available online at: http://ready.arl.noaa.gov/HYSPLIT.php, last access: 25 November 2011, 2011. Dubovik, O. and King, M D.: A flexible inversion algorithm for retrieval of aerosol optical properties from Sun and sky radiance measurements, J. Geophys. Res.-Atmos., 105, 20673–20696, 2000. EC: Environment Canada, National Pollutant Release Inventory, available online at: http://www.ec.gc.ca/inrp-npri/default.asp?lang=En&n=4A577BB9-1, 15 March 2011, 2011. Engel-Cox, J A., Holloman, C H., Coutant, B W., and Hoff, R M.: Qualitative and quantitative evaluation of MODIS satellite sensor data for regional and urban scale air quality, Atmos. Environ., 38, 2495–2509, 2004. Engel-Cox, J A., Hoff, R M., Rogers, R., Dimmick, F., Rush, A C., Szykman, J J., Al-Saadi, J., Chu, D A., and Zell, E R.: Integrating lidar and satellite optical depth with ambient monitoring for 3-dimensional particulate characterization, Atmos. Environ., 40, 8056–8067, 2006. Fayt, C. and Roozendael, M V.: WinDOAS 2.1 – 2001, available online at: http://bro.aeronomie.be/WinDOAS-SUM-210b.pdf, 15 March 2011, 2011. Finlayson-Pitts, B J. and Pitts, J N.: Chemistry of the Upper and Lower Atmosphere, Academic Press, San Diego, California, USA, 5–6, 1999. Frieß, U., Monks, P S., Remedios, J J., Rozanov, A., Sinreich, R., Wagner, T., and Platt, U.: MAX-DOAS O<sub>4</sub> measurements: A new technique to derive information on atmospheric aerosols: 2. Modeling studies, J. Geophys. Res.-Atmos., 111, D14203, http://dx.doi.org/10.1029/2005JD006618doi:10.1029/2005JD006618, 2006. Grainger, J F. and Ring, J.: Anomalous Fraunhofer Line Profiles, Nature, 193, 762, 1962. Greenblatt, G D., Orlando, J J., Burkholder, J B., and Ravishankara, A R.: Absorption-Measurements of Oxygen between 330 nm and 1140 nm, J. Geophys. Res.-Atmos., 95, 18577–18582, 1990. Gupta, P. and Christopher, S. A.: Seven year particulate matter air quality assessment from surface and satellite measurements, Atmos. Chem. Phys., 8, 3311–3324, http://dx.doi.org/10.5194/acp-8-3311-2008doi:10.5194/acp-8-3311-2008, 2008. Harder, J W. and Brault, J W.: Atmospheric measurements of water vapor in the 442-nm region, J. Geophys. Res.-Atmos., 102, 6245–6252, 1997. Hastie, D R., Narayan, J., Schiller, C., Niki, H., Shepson, P B., Sills, D. M L., Taylor, P A., Moroz, W J., Drummond, J W., Reid, N., Taylor, R., Roussel, P B., and Melo, O T.: Observational evidence for the impact of the lake breeze circulation on ozone concentrations in Southern Ontario, Atmos. Environ., 33, 323–335, 1999. Hayden, K., Sills, D., Brook, J., Li, S., Makar, P., Markovic, M., Liu, P., Anlauf, K., O'Brien, J., Lin, Q., and McLaren, R.: Aircraft study of the impact of lake-breeze circulations on trace gases and particles during BAQS-Met 2007, Atmos. Chem. Phys., 11, 10173–10192, http://dx.doi.org/10.5194/acp-11-10173-2011doi:10.5194/acp-11-10173-2011, 2011. Heckel, A., Richter, A., Tarsu, T., Wittrock, F., Hak, C., Pundt, I., Junkermann, W., and Burrows, J. P.: MAX-DOAS measurements of formaldehyde in the Po-Valley, Atmos. Chem. Phys., 5, 909–918, http://dx.doi.org/10.5194/acp-5-909-2005doi:10.5194/acp-5-909-2005, 2005. Heland, J., Schlager, H., Richter, A., and Burrows, J P.: First comparison of tropospheric NO<sub>2</sub> column densities retrieved from GOME measurements and in situ aircraft profile measurements, Geophy. Res. Lett., 29, 1983, http://dx.doi.org/10.1029/2002GL015528doi:10.1029/2002GL015528, 2002. Hendrick, F., Van Roozendael, M., Kylling, A., Petritoli, A., Rozanov, A., Sanghavi, S., Schofield, R., von Friedeburg, C., Wagner, T., Wittrock, F., Fonteyn, D., and De Maziére, M.: Intercomparison exercise between different radiative transfer models used for the interpretation of ground-based zenith-sky and multi-axis DOAS observations, Atmos. Chem. Phys., 6, 93–108, http://dx.doi.org/10.5194/acp-6-93-2006doi:10.5194/acp-6-93-2006, 2006. Holben, B N., Eck, T F., Slutsker, I., Tanre, D., Buis, J P., Setzer, A., Vermote, E., Reagan, J A., Kaufman, Y J., Nakajima, T., Lavenu, F., Jankowiak, I., and Smirnov, A.: AERONET – A federated instrument network and data archive for aerosol characterization, Remote Sens. Environ., 66, 1–16, 1998. Holben, B N., Tanre, D., Smirnov, A., Eck, T F., Slutsker, I., Abuhassan, N., Newcomb, W W., Schafer, J S., Chatenet, B., Lavenu, F., Kaufman, Y J., Castle, J V., Setzer, A., Markham, B., Clark, D., Frouin, R., Halthore, R., Karneli, A., O'Neill, N T., Pietras, C., Pinker, R T., Voss, K., and Zibordi, G.: An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET, J. Geophys. Res.-Atmos., 106, 12067–12097, 2001. 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. Irie, H., Kanaya, Y., Akimoto, H., Iwabuchi, H., Shimizu, A., and Aoki, K.: First retrieval of tropospheric aerosol profiles using MAX-DOAS and comparison with lidar and sky radiometer measurements, Atmos. Chem. Phys., 8, 341–350, http://dx.doi.org/10.5194/acp-8-341-2008doi:10.5194/acp-8-341-2008, 2008. Irie, H., Kanaya, Y., Akimoto, H., Iwabuchi, H., Shimizu, A., and Aoki, K.: Dual-wavelength aerosol vertical profile measurements by MAX-DOAS at Tsukuba, Japan, Atmos. Chem. Phys., 9, 2741–2749, http://dx.doi.org/10.5194/acp-9-2741-2009doi:10.5194/acp-9-2741-2009, 2009. Jacob, D. J.: Introduction to Atmospheric Chemistry, Princeton University Press, Princeton N.J., 1999. Kacenelenbogen, M., Léon, J.-F., Chiapello, I., and Tanré, D.: Characterization of aerosol pollution events in France using ground-based and POLDER-2 satellite data, Atmos. Chem. Phys., 6, 4843–4849, http://dx.doi.org/10.5194/acp-6-4843-2006doi:10.5194/acp-6-4843-2006, 2006. Koelemeijer, R. B A., Homan, C D., and Matthijsen, J.: Comparison of spatial and temporal variations of aerosol optical thickness and particulate matter over Europe, Atmos. Environ., 40, 5304–5315, 2006. Kraus, S.: DOASIS, A Framework Design for DOAS, Ph.D. thesis, University of Heidelberg, Germany, 2006. Kurucz, R L., Furenlid, I J., and Testerman, L.: Solar Flux Atlas from 296 to 1300 nm, National Solar Observatory, Tech. rep., 1984. Ladstätter-Weißenmayer, A., Heland, J., Kormann, R., von Kuhlmann, R., Lawrence, M. G., Meyer-Arnek, J., Richter, A., Wittrock, F., Ziereis, H., and Burrows, J. P.: Transport and build-up of tropospheric trace gases during the MINOS campaign: comparision of GOME, in situ aircraft measurements and MATCH-MPIC-data, Atmos. Chem. Phys., 3, 1887–1902, http://dx.doi.org/10.5194/acp-3-1887-2003doi:10.5194/acp-3-1887-2003, 2003. Lee, H., Irie, H., Kim, Y J., Noh, Y., Lee, C., Kim, Y., and Chun, K J.: Retrieval of Aerosol Extinction in the Lower Troposphere Based on UV MAX-DOAS Measurements, Aerosol Sci. Technol., 43, 502–509, 2009. Levelt, P F., den Oord, G. H. J V., Dobber, M R., Malkki, A., Visser, H., de~Vries, J., Stammes, P., Lundell, J. O V., and Saari, H.: The Ozone Monitoring Instrument, IEEE T. Geosci. Remote, 44, 1093–1101, 2006. Levy, R C., Remer, L A., and Dubovik, O.: Global aerosol optical properties and application to Moderate Resolution Imaging Spectroradiometer aerosol retrieval over land, J. Geophys. Res.-Atmos., 112, D13210, http://dx.doi.org/10.1029/2006JD007815doi:10.1029/2006JD007815, 2007. Li, X., Brauers, T., Shao, M., Garland, R. M., Wagner, T., Deutschmann, T., and Wahner, A.: MAX-DOAS measurements in southern China: retrieval of aerosol extinctions and validation using ground-based in-situ data, Atmos. Chem. Phys., 10, 2079–2089, http://dx.doi.org/10.5194/acp-10-2079-2010doi:10.5194/acp-10-2079-2010, 2010. Lyons, W A. and Cole, H S.: Fumigation and Plume Trapping on the Shores of Lake Michigan During Stable Onshore Flow, J. Appl. Meteorol., 12, 494–510, 1973. Martin, R V., Chance, K., Jacob, D J., Kurosu, T P., Spurr, R. J D., Bucsela, E., Gleason, J F., Palmer, P I., Bey, I., Fiore, A M., Li, Q., Yantosca, R M., and Koelemeijer, R. B A.: An improved retrieval of tropospheric nitrogen dioxide from GOME, J. Geophys. Res., 107, 4437, http://dx.doi.org/10.1029/2001JD001027doi:10.1029/2001JD001027, 2002. 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. Martin, R V., Sioris, C E., Chance, K., Ryerson, T B., Bertram, T H., Wooldridge, P J., Cohen, R C., Neuman, J A., Swanson, A., and Flocke, F M.:~Evaluation of space-based constraints on global nitrogen oxide emissions with regional aircraft measurements over and downwind of eastern North America, J. Geophys. Res., 111, D15308, http://dx.doi.org/10.1029/2005JD006680doi:10.1029/2005JD006680, 2006. McGuire, M L., Jeong, C H., Slowik, J G., Chang, R Y W., Corbin, J C., Lu, G., Mihele, C., Rehbein, P J G., Sills, D M L., Abbatt, J P D., Brook, J R., and Evans, G J Elucidating determinants of aerosol composition through particle-type-based receptor modeling, Atmos. Chem. Phys., 11, 8133–8155, http://dx.doi.org/10.5194/acp-11-8133-2011doi:10.5194/acp-11-8133-2011, 2011. McLaren, R., Salmon, R A., Liggio, J., Hayden, K L., Anlauf, K G., and Leaitch, W R.: Nighttime chemistry at a rural site in the Lower Fraser Valley, Atmos. Environ., 43, 5847–5852, 2004. McLaren, R., Wojtal, P., Majonis, D., McCourt, J., Halla, J. D., and Brook, J.: NO<sub>3</sub> radical measurements in a polluted marine environment: links to ozone formation, Atmos. Chem. Phys., 10, 4187–4206, http://dx.doi.org/10.5194/acp-10-4187-2010doi:10.5194/acp-10-4187-2010, 2010. MOE: Ministry of the Environment, Ontario (MOE): Air Quality in Ontario 2005 Report and Appendix, available online at: http://www.ene.gov.on.ca/environment/en/resources/STD01_076445.html, last access: 25 November 2011, 2011. Müller, J F.: Geographical-Distribution and Seasonal-Variation of Surface Emissions and Deposition Velocities of Atmospheric Trace Gases, J. Geophys. Res.-Atmos., 97, 3787–3804, 1992. NASA: NASA Goddard Space Flight Center LAADS Web – Level 1 and Atmosphere Archive and Distribution System, available online at: http://ladsweb.nascom.nasa.gov/, last access: 25 November 2011, 2010a. NASA: NASA Goddard Space Flight Center Aura Validation Data Center, available online at: http://avdc.gsfc.nasa.gov/, 25 November 2011, 2010b. NASA: NASA Goddard Space Flight Center AERONET – Aerosol Robotic Network, available at: http://aeronet.gsfc.nasa.gov/, last access: 25 November 2011, 2010c. Pelletier, B., Santer, R., and Vidot, J.: Retrieving of particulate matter from optical measurements: A semiparametric approach, J. Geophys. Res.-Atmos., 112, D06208, http://dx.doi.org/10.1029/2005JD006737doi:10.1029/2005JD006737, 2007. Perliski, L M. and Solomon, S.: On the Evaluation of Air-Mass Factors for Atmospheric Near-Ultraviolet and Visible Absorption-Spectroscopy, J. Geophys. Res.-Atmos., 98, 10363–10374, 1993. Plane, J. M C. and Smith, N.: Atmospheric Monitoring By Differential Optical Absorption Spectroscopy, vol 24 of Spectroscopy in Environmental Science, John Wiley & Sons, Inc., West Sussex, UK, Chapter 5, p 223, 1995. Platt, U.: Differential Optical Absorption Spectroscopy (DOAS), vol. 127 of Air Monitoring by Spectroscopic Technique, Chemical Analysis Series, John Wiley & Sons, Inc., Hoboken, NJ, USA, p 27, 1994. Platt, U. and Perner, D.: Direct Measurements of Atmospheric CH<sub>2</sub>O, HNO<sub>2</sub>, O<sub>3</sub>, NO<sub>2</sub>, and SO<sub>2</sub> by Differential Optical Absorption in the Near UV, J. Geophys. Res., 85, 7453–7458, 1980. Platt, U. and Stutz, J.: Differential Optical Absorption Spectroscopy: Principles and Applications, Springer, Berlin, Heidelberg, Germany, 2008. Reid, N W., Niki, H., Hastie, D., Shepson, P., Roussel, P., Melo, O., Mackay, G., Drummond, J., Schiff, H., Poissant, L., and Moroz, W.: The southern Ontario oxidant study (SONTOS): Overview and case studies for 1992, Atmos. Environ., 30, 2125–2132, 1996. Schaap, M., Apituley, A., Timmermans, R. M. A., Koelemeijer, R. B. A., and de Leeuw, G.: Exploring the relation between aerosol optical depth and PM$_2.5$ at Cabauw, the Netherlands, Atmos. Chem. Phys., 9, 909–925, http://dx.doi.org/10.5194/acp-9-909-2009doi:10.5194/acp-9-909-2009, 2009. Sills, D. M. L., Brook, J. R., Levy, I., Makar, P. A., Zhang, J., and Taylor, P. A.: Lake breezes in the southern Great Lakes region and their influence during BAQS-Met 2007, Atmos. Chem. Phys., 11, 7955–7973, http://dx.doi.org/10.5194/acp-11-7955-2011doi:10.5194/acp-11-7955-2011, 2011. Sinreich, R., Friess, U., Wagner, T., and Platt, U.: Multi axis differential optical absorption spectroscopy (MAX-DOAS) of gas and aerosol distributions, Faraday Discuss., 130, 153–164, 2005. Solomon, S., Schmeltekopf, A L., and Sanders, R W.: On the Interpretation of Zenith Sky Absorption Measurements, J. Geophys. Res., 92, 8311–8319, 1987. Strawbridge, K. B., and Synder, B. J.: Planetary boundary layer height determination during Pacific 2001 using the advantage of a scanning lidar instrument, Atmos. Environ., 38, 5861–5871, 2004. Torres, O., Bhartia, P K., Herman, J R., Ahmad, Z., and Gleason, J.: Derivation of aerosol properties from satellite measurements of backscattered ultraviolet radiation: Theoretical basis, J. Geophys. Res.-Atmos., 103, 17099–17110, 1998. UWYO: University of Wyoming (UWYO), College of Engineering, Department of Atmospheric Science Atmospheric Soundings, available online at: http://weather.uwyo.edu/upperair/sounding.html, last access: 25 November 2011, 2010. Vandaele, A C., Hermans, C., Simon, P C., Carleer, M., Colin, R., Fally, S., Merienne, 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., von Friedeburg, C., Wenig, M., Otten, C., and Platt, U.: UV-visible observations of atmospheric O<sub>4</sub> absorptions using direct moonlight and zenith-scattered sunlight for clear-sky and cloudy sky conditions, J. Geophys. Res.-Atmos., 107, 4424, http://dx.doi.org/10.1029/2001JD001026doi:10.1029/2001JD001026, 2002. Wagner, T., Dix, B., von Friedeburg, C., 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.-Atmos., 109, D22205, http://dx.doi.org/10.1029/2004JD004904doi:10.1029/2004JD004904, 2004. Wagner, T., Burrows, J. P., Deutschmann, T., Dix, B., von Friedeburg, C., Frieß, U., Hendrick, F., Heue, K.-P., Irie, H., Iwabuchi, H., Kanaya, Y., Keller, J., McLinden, C. A., Oetjen, H., Palazzi, E., Petritoli, A., Platt, U., Postylyakov, O., Pukite, J., Richter, A., van Roozendael, M., Rozanov, A., Rozanov, V., Sinreich, R., Sanghavi, S., and Wittrock, F.: Comparison of box-air-mass-factors and radiances for Multiple-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) geometries calculated from different UV/visible radiative transfer models, Atmos. Chem. Phys., 7, 1809–1833, http://dx.doi.org/10.5194/acp-7-1809-2007doi:10.5194/acp-7-1809-2007, 2007. 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., Beirle, S., Brauers, T., Deutschmann, T., Frieß, U., Hak, C., Halla, J.D., Heue, K. P., Junkermann, W., Li, X., Platt, U., and Pundt-Gruber, I.: Inversion of tropospheric profiles of aerosol extinction and HCHO and NO<sub>2</sub> concentrations from MAX-DOAS observations in Milano in summer 2003 and comparison with independent data sets, Atmos. Meas. Tech. Discuss., 4, 3891–3964, http://dx.doi.org/10.5194/amtd-4-3891-2011doi:10.5194/amtd-4-3891-2011, 2011. Wang, J. and Christopher, S A.: Intercomparison between satellite-derived aerosol optical thickness and PM$_2.5$ mass: Implications for air quality studies, Geophys. Res. Lett., 30, 2095, http://dx.doi.org/10.1029/2003GL018174doi:10.1029/2003GL018174, 2003. Wenig, M O., Cede, A M., Bucsela, E J., Celarier, E A., Boersma, K F., Veefkind, J P., Brinksma, E J., Gleason, J F., and Herman, J R.: Validation of OMI tropospheric NO<sub>2</sub> column densities using direct-Sun mode Brewer measurements at NASA Goddard Space Flight Center, J. Geophys. Res.-Atmos., 113, D16S45, http://dx.doi.org/10.1029/2007JD008988doi:10.1029/2007JD008988, 2008. 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. Zieger, P., Weingartner, E., Henzing, J., Moerman, M., de Leeuw, G., Mikkilä, J., Ehn, M., Petäjä, T., Clémer, K., van Roozendael, M., Yilmaz, S., Frieß, U., Irie, H., Wagner, T., Shaiganfar, R., Beirle, S., Apituley, A., Wilson, K., and Baltensperger, U.: Comparison of ambient aerosol extinction coefficients obtained from in-situ, MAX-DOAS and LIDAR measurements at Cabauw, Atmos. Chem. Phys., 11, 2603–2624, http://dx.doi.org/10.5194/acp-11-2603-2011doi:10.5194/acp-11-2603-2011, 2011.