Total ozone retrieval from GOME UV spectral data using the weighting function DOAS approach

[摘要] A new algorithm approach called Weighting Function Differential OpticalAbsorption Spectroscopy (WFDOAS) is presented which has been developed toretrieve total ozone columns from nadir observations of the Global OzoneMonitoring Experiment.By fitting the vertically integrated ozone weightingfunction rather than ozone cross-section to the sun-normalized radiances, adirect retrieval of vertical column amounts is possible. The new WFDOASapproach takes into account the slant path wavelength modulation that isusually neglected in the standard DOAS approach using single airmassfactors.This paper focuses on the algorithm description and erroranalysis, while in a companion paper by Weber et al. (2004) a detailedvalidation with groundbased measurements is presented. For the first timeseveral auxiliary quantities directly derived from the GOME spectral rangesuch as cloud-top-height and cloud fraction (O₂-A band) and effectivealbedo using the Lambertian Equivalent Reflectivity (LER) near 377nm areused in combination as input to the ozone retrieval. In addition the varyingozone dependent contribution to the Raman correction in scattered lightknown as Ring effect has been included. The molecular ozone filling-inthat is accounted for in the new algorithm has the largest contributionto the improved total ozone results from WFDOAS compared to theoperational product. The precision of the total ozone retrieval is estimatedto be better than 3% for solar zenith angles below 80°.

[学科分类] 大气科学