AMT Atmospheric Measurement Techniques AMT Atmos. Meas. Tech. 1867-8548 Copernicus Publications Göttingen, Germany 10.5194/amt-5-901-2012 NO<sub>2</sub> measurements in Hong Kong using LED based long path differential optical absorption spectroscopy Chan K. L. 1 Pöhler D. 2 Kuhlmann G. 1 Hartl A. 1 Platt U. 2 Wenig M. O. 1 School of Energy and Environment, City University of Hong Kong, Hong Kong, China Institute for Environmental Physics, Heidelberg University, Heidelberg, Germany 03 05 2012 5 5 901 912 Copyright: © 2012 K. L. Chan et al. 2012 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://amt.copernicus.org/articles/5/901/2012/amt-5-901-2012.html The full text article is available as a PDF file from https://amt.copernicus.org/articles/5/901/2012/amt-5-901-2012.pdf

In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO<sub>2</sub>) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO<sub>2</sub> levels in the Kowloon Tong and Mongkok district of Hong Kong and we compare the measurement results to mixing ratios reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (<i>R</i> = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO<sub>2</sub> data product. Monthly averaged LP-DOAS and OMI measurements correlate well (<i>R</i> = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time (13:30–14:30 LT – local time).

 References 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, <a href="http://dx.doi.org/10.5194/acp-3-2225-2003">https://doi.org/10.5194/acp-3-2225-2003</a>, 2003. Bey, I., Jacob, D., Yantosca, R., Logan, J., Field, B., Fiore, A., Li, Q., Liu, H., Mickley, L., and Schultz, M.: Global modeling of tropospheric chemistry with assimilated meteorology: Model description and evaluation, J. Geophys. Res., 106, 23073, <a href="http://dx.doi.org/10.1029/2001JD000807">https://doi.org/10.1029/2001JD000807</a>, 2001. Boersma, K. F., Eskes, H. J., Veefkind, J. P., Brinksma, E. J., van der&nbsp;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, <a href="http://dx.doi.org/10.5194/acp-7-2103-2007">https://doi.org/10.5194/acp-7-2103-2007</a>, 2007. Bucsela, E., Celarier, E., Wenig, M., Gleason, J., Veefkind, P., Boersma, K., 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.&nbsp;P., Richter, A., Dehn, A., Deters, B., Himmelmann, S., Voigt, S., and Orphal, J.: Atmospheric remote sensing reference data from GOME&nbsp;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. Dunlea, E. J., Herndon, S. C., Nelson, D. D., Volkamer, R. M., San Martini, F., Sheehy, P. M., Zahniser, M. S., Shorter, J. H., Wormhoudt, J. C., Lamb, B. K., Allwine, E. J., Gaffney, J. S., Marley, N. A., Grutter, M., Marquez, C., Blanco, S., Cardenas, B., Retama, A., Ramos Villegas, C. R., Kolb, C. E., Molina, L. T., and Molina, M. J.: Evaluation of nitrogen dioxide chemiluminescence monitors in a polluted urban environment, Atmos. Chem. Phys., 7, 2691–2704, <a href="http://dx.doi.org/10.5194/acp-7-2691-2007">https://doi.org/10.5194/acp-7-2691-2007</a>, 2007. Greenblatt, G., Orlando, J., Burkholder, J., and Ravishankara, A.: Absorption measurements of oxygen between 330&nbsp;and 1140 nm, J. Geophys. Res., 95, 18577–18582, 1990. Harder, J.&nbsp;W. and Brault, J.&nbsp;W.: Atmospheric measurements of water vapor in the 442 nm region, J. Geophys. Res., 102, 6245–6252, 1997. Kraus, S.: DOASIS A Framework Design for DOAS, Ph.D.&nbsp;thesis, Combined Faculties for Mathematics and for Computer Science, University of Mannheim, Germany, 2005. Lau, J., Hung, W., Cheung, C., and Yuen, D.: Contributions of roadside vehicle emissions to general air quality in Hong Kong, Transport. Res. Pt.&nbsp;D, 13, 19–26, 2008. Lee, D.&nbsp;S., Köhler, I., Grobler, E., Rohrer, F., Sausen, R., Gallardo-Klenner, L., Olivier, J. G.&nbsp;J., Dentener, F.&nbsp;J., , and Bouwman, A.: Estimations of Global NO<i><sub>x</sub></i> Emissions and Their Uncertainties, Atmos. Environ., 31, 1735–1749, 1997. Levelt, P.&nbsp;F., van&nbsp;den Oord, G. H.&nbsp;J., Dobber, M.&nbsp;R., Malkki, A., Visser, H., de&nbsp;Vries, J., Stammes, P., Lundell, J. O.&nbsp;V., , and Saari, H.: The Ozone Monitoring Instrument, IEEE T. Geosci. Remote, 44, 1093–1101, 2006. Merten, A., Tschritter, J., and Platt, U.: New Design of DOAS-Long-path Telescopes based on fiber optics, Appl. Optics, 50, 783–754, 2011. Palmer, P., Jacob, D., Chance, K., Martin, R., Spurr, R., Kurosu, T., Bey, R.&nbsp;Y., and Fiore, A.: Air mass factor formulation for spectroscopic measurements from satellites: Application to formaldehyde retrievals from the Global Ozone Monitoring Experiment, J. Geophys. Res., 106, 14539–14550, 2001. Platt, U., Perner, D., and Patz, H.: Simultaneous measurement of atmospheric CH<sub>2</sub>O, O<sub>3</sub>and NO<sub>2</sub> by differential optical absorption, J. Geophys. Res., 84, 6329–6335, 1979. Rothman, L., Barbe, A., Benner, D.&nbsp;C., Brown, L., Camy-Peyret, C., Carleer, M., Chance, K., Clerbaux, C., Dana, V., Devi, V., Fayt, A., Flaud, J.-M., Gamache, R., Goldman, A., Jacquemart, D., Jucks, K., Lafferty, W., Mandin, J.-Y., Massie, S., Nemtchinov, V., Newnham, D., Perrin, A., Rinsland, C., Schroeder, J., Smith, K., Smith, M., Tang, K., Toth, R., Auwera, J.&nbsp;V., Varanasi, P., and Yoshino, K.: The HITRAN molecular spectroscopic database: edition of 2000 including updates through 2001, J. Quant. Spectrosc. Ra., 82, 5–44, 2003. Solomon, S., Schmeltekopf, A.&nbsp;L., and Sanders, R.&nbsp;W.: On the interpretation of zenith sky measurements, J. Geophys. Res., 92, 8311–8319, 1987. Solomon, S., Portmann, R.&nbsp;W., Sanders, R.&nbsp;W., Daniel, J.&nbsp;S., Madsen, W., Bartram, B., and Dutton, E.&nbsp;G.: On the role of nitrogen dioxide in the absorption of solar radiation, J. Geophys. Res., 104, 12047–12058, 1999. Stutz, J. and Platt, U.: Numerical Analysis and Estimation of the Statistical Error of Differential Optical Absorption Spectroscopy Measurements with Least-Squares methods, Appl. Optics, 35, 6041–6053, 1996. Stutz, J. and Platt, U.: Improving longpath differential optical absorption spectroscopy with a quartz-fiber mode mixer, Appl. Optics, 36, 1105–1115, 1997. Vandaele, A.&nbsp;C., Hermans, C., Simon, P.&nbsp;C., Carleer, M., Colin, R., Fally, S., Mérienne, M.&nbsp;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. Voigt, S., Orphal, J., Bogumil, K., and Burrows, J.&nbsp;P.: The temperature dependence (203–293 K) of the absorption cross sections of O<sub>3</sub> in the 230–850 nm region measured by Fourier-transform spectroscopy, J. Photochem. Photobiol., 143, 1–9, 2001. Voigt, S., Orphal, J., and Burrows, J.&nbsp;P.: The temperature and pressure dependence of the absorption cross-sections of NO<sub>2</sub> in the 250–800 nm region measured by Fourier-transform spectroscopy, J. Photochem. Photobiol., 149, 1–7, 2002. Volkamer, R., Spietz, P., Burrows, J., and Platt, U.: High-resolution absorption cross-section of Glyoxal in the UV/vis and IR spectral ranges, J. Photochem. Photobiol., 172, 35–46, <a href="http://dx.doi.org/10.1016/j.jphotochem.2004.11.011">https://doi.org/10.1016/j.jphotochem.2004.11.011</a>, 2005. Wenig, M.&nbsp;O.: Satellite Measurement of Long-Term Global Tropospheric Trace Gas Distributions and Source Strengths – Algorithm Development and Data Analysis, Ph.D.&nbsp;thesis, University of Heidelberg, Germany, 2001. Wenig, M.&nbsp;O., Cede, A.&nbsp;M., Bucsela, E.&nbsp;J., Celarier, E.&nbsp;A., Boersma, K.&nbsp;F., Veefkind, J.&nbsp;P., Brinksma, E.&nbsp;J., Gleason, J.&nbsp;F., and Herman, J.&nbsp;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., 133, D16S45, <a href="http://dx.doi.org/10.1029/2007JD008988">https://doi.org/10.1029/2007JD008988</a>, 2008. Zhang, Q., Streets, D.&nbsp;G., He, K., Wang, Y., Richter, A., Burrows, J.&nbsp;P., Uno, I., Jang, C.&nbsp;J., Chen, D., Yao, Z., and Lei, Y.: NO<i><sub>x</sub></i> emission trends for China, 1995–2004: The view from the ground and the view from space, J. Geophys. Res., 112, D22306, <a href="http://dx.doi.org/10.1029/2007JD008684">https://doi.org/10.1029/2007JD008684</a>, 2007.