Atmospheric Measurement Techniques Discussions www.atmos-meas-tech-discuss.net 1867-8610 2 4 2009 10.5194/amtd-2-1663-2009 http://www.atmos-meas-tech-discuss.net/2/1663/2009/ http://www.atmos-meas-tech-discuss.net/2/1663/2009/amtd-2-1663-2009.html http://www.atmos-meas-tech-discuss.net/2/1663/2009/amtd-2-1663-2009.pdf 1663 1692 2009-07-20 Determination of an effective trace gas mixing height by differential optical absorption spectroscopy (DOAS) B. Zhou binzhou@fudan.edu.cn S. N. Yang S. S. Wang T. Wagner Department of Environmental Science and Engineering, Fudan University, Shanghai, China Max Planck Institute for Chemistry, Mainz, Germany A new method for the determination of the Mixing layer Height (MH) by the DOAS technique is proposed in this article. The MH can be retrieved by a combination of active DOAS and passive DOAS observations of atmospheric trace gases; here we focus on observations of NO₂. Because our observations are sensitive to the vertical distribution of trace gases, we refer to the retrieved layer height as an ''effective trace gas mixing height'' (ETMH). By analyzing trace gas observations in Shanghai over one year (1017 hourly means in 93 days in 2007), the retrieved ETMH was found to range between 0.1 km and 2.8 km (average is 0.78 km); more than 90% of the measurements yield an ETMH between 0.2 km and 2.0 km. The seasonal and diurnal variation of the ETMH shows good agreement with mixing layer heights derived from meteorological observations. We investigated the relationship of the derived ETMH to temperature and wind speed and found correlation coefficients of 0.65 and 0.37, respectively. Also the wind direction has an impact on the measurement to some extent. Especially in cases when the air flow comes from highly polluted areas and the atmospheric lifetime of NO₂ is long (e.g. in winter), the NO₂ concentration at high altitudes over the measurement site can be enhanced, which leads to an overestimation of the ETMH. Enhanced NO₂ concentrations in the free atmosphere and heterogeneity within the mixing layer can cause additional uncertainties. Our method could be easily extended to other species like e.g. SO₂, HCHO or Glyoxal. Simultaneous studies of these molecules could yield valuable information on their respective atmospheric lifetimes. Berman,~S., Yeong,~J K., Zhang,~J., and Rao,~T.: Uncertainties in estimating the mixing depth~– comparing three mixing-depth models with profiler measurements, Atmos. Environ., 31, 3023–3039, 1997. Bruns,~M., Buehler,~S A., Burrows,~J P., Richter,~A., Rozanov,~A., Wang,~P., Heue,~K P., Platt,~U., Pundt,~I., and Wagner,~T.: \chemNO_2 Profile retrieval using airborne multi axis UV-visible skylight absorption measurements over central Europe, Atmos. Chem. Phys., 6, 3049–3058, 2006. Chen,~D., Zhou,~B., Beirle,~S., Chen,~L M., and Wagner,~T.: Tropospheric \chemNO_2 column densities deduced from zenith-sky DOAS measurements in Shanghai, China, and their application to satellite validation, Atmos. Chem. Phys., 9, 3641–3662, 2009. Evangelisti,~F., Baroncelli,~A., Bonasoni,~P., Giovanelli,~G., and Ravegnani,~F.: Differential optical absorption spectrometer for measurement of tropospheric pollutants, Appl. Optics, 34, 2737–2744, 1995. Febo,~A., Perrino,~C., and Allegrini,~I.: Measurement of nitrous acid in Milan, Italy, by DOAS and diffusion ednuders [J], Atmos. Environ., 30, 3599–3609, 1996. García,~M A., S'anchez,~M L., de Torre,~B., and Pérez,~I A.: Characterisation of the mixing height temporal evolution by means of a~laser dial system in an urban area – intercomparison results with a~model application, Ann. Geophys., 25, 2119–2124, 2007. He,~Q S., Mao,~J T., Chen,~J Y., and Hu,~Y Y.: Observational and modelling studies of urban atmospheric boundary-layer height and its evolution mechanisms, Atmos. Environ., 40, 1064–1077, 2006. Hönninger,~G. and Platt,~U.: The role of \chemBrO and its vertical distribution during surface ozone depletion at Alert, Atmos. Environ., 36, 2481–2489, 2002. Kourtidis,~K., Ziomas,~I., Zerefos,~C., Gousopoulos,~A., Balis,~D., and Tzoumaka,~P.: Benzene and toluene levels measured with a~commercial DOAS system in Thessaloniki, Atmos. Environ., 34, 1471–1480, 2000. Noxon,~J F.: Nitrogen dioxide in the stratosphere and troposphere measured by ground-based absorption spectroscopy, Science, 189, 547–549, 1975. Perner,~D. and Platt,~U.: Detection of nitrous acid in the atmosphere by differential optical absorption, Geophys. Res. Lett., 6, 917–920, 1979. Platt,~U.: Differential optical absorption spectroscopy (DOAS), in: Air monitoring by spectroscopic techniques, edited by: Sigrist,~M W., Chem. Anal. Ser., 127, 27–84, 1994. Platt,~U. and Stutz,~J.: Differential Optical Absorption Spectroscopy – Principles and Applications, Springer-Verlag Berlin Heidelberg, 2008. Qi,~F., Liu,~W Q., Zhou,~B., Li,~Z B., and Chui,~Y J.: Improving DOAS System Measurement Precision with Artificial Neutral Network Method, Acta Optica Sinica, 22, 1346–1349, 2002. Seibert,~P.,~Beyrich,~F.,~Gryning,~S.-E., Joffre,~S., Rasmussen,~A., and Tercier,~P.: Review and intercomparison of operational methods for the determination of the mixing height, Atmos. Environ., 34, 1001–1027, 2000. 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, 1999. Vandaele,~A C., Fayt,~C., Hendrick,~F., Hermans,~C., Humbled,~F., van Roozendael,~M., Gil,~M., Navarro,~M., Puentedura,~O., Yela,~M., Braathen,~G., Stebel,~K., Tørnkvist,~K., Johnston,~P., Kreher,~K., Goutail,~F., Mieville,~A., Pommereau,~J.-P., Khaikine,~S., Richter,~A., Oetjen,~H., Wittrock,~F., Bugarski,~S., Frie,~U., Pfeilsticker,~K., Sinreich,~R., Wagner,~T., Corlett,~G., and Leigh,~R.: An intercomparison campaign of ground-based UV-visible measurements of \chemNO_2, \chemBrO, and \chemOClO slant columns: Methods of analysis and results for \chemNO_2, J. Geophys. Res., 110, D08305, doi:10.1029/2004JD005423, 2005. Yang,~Y J.,Tan,~J G., Zheng,~Y F., and Cheng,~S.H.: Study on the atmospheric stabilities and the thickness of atmospheric mixed layer during recent 15 years in Shanghai, Scientia Meteorolo Gica Sinica, 26, 537–541, 2006. Zhou~B., Hao,~N., and Chen,~L M.: A~study on the effect of Fraunhofer structure on the measurement of atmospheric pollutants with differential optical absorption spectroscopy, Acta Phys. Sin-Ch. Ed., 9, 4445–4450, 2005. Zhou,~B., Liu,~W Q., Qi,~F. Li,~Z B., and Chui,~Y J., Error analysis in Differential Optical Absorption Spectroscopy, Acta Optica Sinica, 22, 957–961, 2002.