Retrieval of CO from SCIAMACHY onboard ENVISAT: detection of strongly polluted areas and seasonal patterns in global CO abundances

[摘要] SCIAMACHY onboard the European environmental research satelliteENVISAT is an UV/visible/near-infrared spectrometer providing 3near infrared channels covering wavelengths from 1-1.75 µm,1.94-2.04 µm and 2.26-2.38 µm with moderate spectralresolution (0.22-1.5nm). From their structured absorption in thesespectral regions, we can quantitatively determine the total columndensities of the greenhouse gases CO₂, CH₄,N₂O and H₂O as well as of CO. Amodified DOAS algorithm based on optimal estimation (IMAP-DOAS) hasbeen developed at the University of Heidelberg to account for thepeculiarities of these absorbers. CO is a relatively weak absorberwhose spectral signature is overlapped by strong CH₄ andH₂O absorptions. Hence, retrieval of CO from SCIAMACHYspectra (within 2.26-2.38 µm) is a challenging task.Therefore, the calibration of the raw spectra with respect to darkcurrent issues and nonlinearity were analysed in detail andsubstantially improved to enable reasonable retrieval of CO. Thispaper focusses on first results of the CO retrieval where varioussources like biomass burning events and their seasonal variabilitycan be clearly identified.

[学科分类] 大气科学