Bovensmann, Heinrich
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Bovensmann, Heinrich
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Bovensmann, Heinrich
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Item type:Publication, Solar Occultation Measurements with SCIAMACHY in the UV-visible-IR Wavelength Region(2004-05-26); ; ; The focus of this thesis is the evaluation of the first solar occultation measurements performed by SCIAMACHY onboard ENVISAT in the UV-vis-NIR wavelength range. Vertical trace gas concentration profiles have been retrieved from atmospheric measurement spectra, fitting the differential structures of extinction signals. An introduction is given about the foundations of the occultation geometry. The underlying studies are separated into theoretical investigations about the sensitivity of the instrument with respect to atmospheric constituents and trace gas retrievals from the first real measurement data. It is shown that the spectrometer works as expected in occultation geometry. Spectral data have a high signal-to-noise ratio except for the UV wavelength range at low altitudes. First standard data products of ozone and nitrogen dioxide vertical profiles in the stratosphere and upper troposphere have been produced with errors in the order of 10 and 15 %, respectively. The inversion algorithm is based on the optimal estimation method or, alternatively, on the eigenvector decomposition method. Correction algorithms have been implemented concerning the tangent height of the line of sight and the pointing on the solar disk. The radiative transfer model is based on the Lambert-Beer law of extinction. The retrieval algorithm assumes the measured spectra to consist only of transmitted light rather than scattered light. Theoretical studies have been performed to demonstrate that this assumption is true. An estimation of different error sources is discussed as well.doctoral thesis1530 183 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Stratospheric O3, NO2, and NO3 number density profile from SCIAMACHY lunar occultation spectroscopic measurements: Retrieval, validation and interpretation(2005-11-21); ; ; Stratospheric profiles of O3, NO2, and NO3 were retrieved from lunar transmitted spectra measured by SCIAMACHY over high southern latitude (60Ã °S - 90Ã °S), from March to June 2003 and January to June 2004. The global spectral fitting method by the differential optical depth approach was applied to simultaneously fit O3 and NO2 using the spectral range of 430-460 nm and 510-560 nm. Furthermore, NO3 was fitted using the visible spectral range of 615-680 nm containing NO3 intense absorption bands at 623 nm and 662 nm. Validation of the retrieved SCIAMACHY O3 and NO2 profiles were carried out. O3 profiles were compared with HALOE,POAM-III, SAGE-II and -III, and MIPAS. Whereas NO2 profiles were compared with HALOE, MIPAS, and SAGE-III. The validation results show that the quality of SCIAMACHY O3profiles is high, within 10-25% and 10-35% for O3 and NO2 respectively. To test our current understanding of NO3 chemistry, the retrieved NO3 vertical profiles were compared with a full photochemical model and a relatively simple steady state model. The calculations from a full photochemical model constrained by retrieved O3 and analyzed ECMWF temperatures in the altitude range between 24 to 45 km. Below about 35-40 km, observed NO3 is well reproduced by photochemical steady state calculations. Differences between observed and modeled NO3 are within the estimated accuracy of 20-35%, demonstrating that we have a reasonable understanding of the behavior of NO3 in the polar stratosphere.doctoral thesis404 587