MAX-DOAS measurements of formaldehyde in the Po-Valley

Abstract

Abstract. During the first measurement campaign of the EU FORMAT project in summer 2002 near Milan, northern Italy, ground-based scattered light differential optical absorption spectroscopy (DOAS) measurements were performed using a new multi-axis instrument. From the data set of this four week measurement period, the detailed analysis results of three days, 12-14 August, are presented exemplary. Slant column densities for formaldehyde (HCHO) and the oxygen dimer (O 4 ) have been retrieved, employing fitting windows from 335 nm to 357 nm and 350 nm to 360 nm respectively. In order to convert slant into vertical columns radiative transfer calculations were perfomred using aerosol parameters derived from the actual O 4 measurements. By analysing the measurements from different viewing directions (zenith, 4x off-axis) vertical profile information, and in particular mixing ratios for the boundary layer have been derived for the first time for HCHO with a multi-axis DOAS (MAX-DOAS) instrument. HCHO vertical columns are in the range of 5 to 20·10 15 molec/cm 2 with an relative error of about 15%. This corresponds to HCHO mixing ratios in the boundary layer of 0.7 ppb to 4.2 ppb, which is in excellent agreement with simultaneous measurements from both a Hantzsch in-situ and a long-path DOAS instrument operated at the same place.

Evaluation of tropospheric SO<sub>2</sub> retrieved from MAX-DOAS measurements in Xianghe, China

“…It is based on the measurement of sunlight scattered at multiple elevation angles towards the horizon, thus increasing the sensitivity to absorbers present close to the ground compared to the zenith viewing geometry (Hönninger et al, 2004). MAX-DOAS studies published so far have been mainly focused on the retrieval of NO 2 (e.g., Wittrock et al, 2004;Vlemmix et al, 2010;Frins et al, 2012;Hendrick et al, 2014;Ma et al, 2013;Wang et al, 2014), halogen oxides like BrO and IO (e.g., Frieß et al, 2011;Großmann et al, 2013), formaldehyde (e.g., Heckel et al, 2005;Wagner et al, 2011), and aerosols (e.g., Wagner et al, 2004;Frieß et al, 2006;Clémer et al, 2010). A lot of work has been done on MAX-DOAS measurements of volcanic SO 2 (e.g., Bobrowski et al, 2007;Galle et al, 2010), but so far only a few studies deal with MAX-DOAS observations of this species in polluted areas (e.g., Irie et al, 2011;Lee et al, 2008;Wu et al, 2013), despite the fact that, as for other trace gases like NO 2 , HCHO, and BrO, the combination of both surface concentration and VCD retrievals makes MAX-DOAS a useful technique for validating SO 2 satellite data.…”

Mobile MAX-DOAS observations of tropospheric trace gases

“…Tropospheric profile retrievals are mainly based on observations from low elevation angles (below ∼ 20 • ) and can yield several pieces of information, with the highest vertical resolution close to the surface (e.g. Hönninger and Platt, 2002;Heckel et al, 2005). They can usually be performed only under cloud free conditions.…”

“…In recent years Multi-AXis-Differential Optical Absorption Spectroscopy (MAX-DOAS) observations have become a widely and successfully used technique for the remote sensing of tropospheric trace gases and aerosols (Leser et al, 2003;Van Roozendael et al, 2003;Wittrock et al, 2003; Correspondence to: T. Wagner (thomas.wagner@mpch-mainz.mpg.de) Hönninger et al, 2004a, b;Sinreich et al, 2005;Heckel et al, 2005;Frieß et al, 2006;Fietkau et al, 2007;Theys et al, 2007;Wagner et al, 2004Wagner et al, , 2007aWagner et al, , b, 2009Irie et al, 2008). MAX-DOAS instruments observe scattered sun light under different (mostly slant) viewing angles, providing high sensitivity to tropospheric trace gases and aerosols.…”

Determination of aerosol properties from MAX-DOAS observations of the Ring effect

“…Thus, from the measured strength of the Ring effect, information on aerosols and clouds can be obtained (Park et al, 1986;Joiner et al, , 2002Joiner et al, , 2004de Beek et al, 2001;Wagner et al,496 T. Wagner et al: Determination of aerosol properties from MAX-DOAS observations of the Ring effect this study we focus on the potential to retrieve aerosol information from observations of the Ring effect using a ground based Multi-Axis-DOAS (MAX-DOAS) instrument. MAX-DOAS instruments observe scattered sun light under a variety of elevation angles (Hönninger and Platt, 2002;Leser et al, 2003;Bobrowski et al, 2003;van Roozendael et al, 2003;Wittrock et al, 2004;Hönninger et al, 2004;Heckel et al, 2005;Wagner et al, 2004Wagner et al, , 2007bFrieß et al, 2006;Fietkau et al, 2007;Theys et al, 2007). The MAX-DOAS observations used in this study make simultaneous measurements in three different azimuth directions.…”