MAX-DOAS measurements of atmospheric trace gases in Ny-Ålesund - Radiative transfer studies and their application

Abstract

Abstract.A new approach to derive tropospheric concentrations of some atmospheric trace gases from ground-based UV/vis measurements is described. The instrument, referred to as the MAX-DOAS, is based on the well-known UV/vis instruments, which use the sunlight scattered in the zenith sky as the light source and the method of Differential Optical Absorption Spectroscopy (DOAS) to derive column amounts of absorbers like ozone and nitrogen dioxide. Substantial enhancements have been applied to this standard setup to use different lines of sight near to the horizon as additional light sources (MAX -multi axis). Results from measurements at Ny-Ålesund (79 • N, 12 • E) are presented and interpreted with the full-spherical radiative transfer model SCIATRAN. In particular, measurements of the oxygen dimer O 4 which has a known column and vertical distribution in the atmosphere are used to evaluate the sensitivity of the retrieval to parameters such as multiple scattering, solar azimuth, surface albedo and refraction in the atmosphere and also to validate the radiative transfer model. As a first application, measurements of NO 2 emissions from a ship lying in Ny-Ålesund harbour are presented. The results of this study demonstrate the feasibility of long term UV/vis multi axis measurement that can be used to derive not only column amounts of different trace gases but also some information on the vertical location of these absorbers.

Intercomparison of slant column measurements of NO<sub>2</sub> and O<sub>4</sub> by MAX-DOAS and zenith-sky UV and visible spectrometers

“…1 (Hönninger and Platt, 2002;Hönninger et al, 2004;Wittrock et al, 2004). Because the path to the last scattering point is confined to lower altitudes at elevations close to the horizon, measurements at several elevations down almost to the horizon yield information about the vertical profile of the absorber within the troposphere.…”

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.…”

NO<sub>2</sub> observations over the western Pacific and Indian Ocean by MAX-DOAS on <i>Kaiyo</i>, a Japanese research vessel

“…Hönninger et al, 2004;Wagner et al, 2004;Wittrock et al, 2004;Sinreich et al, 2005;Frieß et al, 2006). It is useful for measuring a priori profiles for satellite retrievals and for validating chemical transport models.…”