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

摘要

A new approach to derive tropospheric concentrations of someatmospheric trace gases from ground-based UV/vis measurements isdescribed. The instrument, referred to as the MAX-DOAS, is basedon the well-known UV/vis instruments, which use the sunlightscattered in the zenith sky as the light source and the method ofDifferential Optical Absorption Spectroscopy (DOAS) to derivecolumn amounts of absorbers like ozone and nitrogen dioxide.Substantial enhancements have been applied to this standard setupto use different lines of sight near to the horizon as additionallight sources (MAX - multi axis). Results from measurements atNy-Ålesund (79° N, 12° E) are presented andinterpreted with the full-spherical radiative transfer modelSCIATRAN. In particular, measurements of the oxygen dimerO₄ which has a known column and vertical distribution inthe atmosphere are used to evaluate the sensitivity of theretrieval to parameters such as multiple scattering, solarazimuth, surface albedo and refraction in the atmosphere and alsoto validate the radiative transfer model. As a first application,measurements of NO₂ emissions from a ship lying in Ny-Ålesundharbour are presented. The results of this studydemonstrate the feasibility of long term UV/vis multi axismeasurement that can be used to derive not only column amounts ofdifferent trace gases but also some information on the verticallocation of these absorbers.