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Solar spectrometry for determination of tropospheric water vapor / Bernd Sierk (2001)  

Public Titre : Solar spectrometry for determination of tropospheric water vapor Type de document : Thèse/HDR Auteurs : Bernd Sierk, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2001 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 62 Importance : 212 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-04-8 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] absorption atmosphérique [Termes IGN] campagne d'expérimentation [Termes IGN] modèle de transfert radiatif [Termes IGN] propagation troposphérique [Termes IGN] rayonnement solaire [Termes IGN] spectromètre [Termes IGN] spectrométrie [Termes IGN] traitement de données [Termes IGN] troposphère [Termes IGN] vapeur d'eau Résumé : (Auteur) This study reports the development of a new instrumental approach to ground based remote sensing of tropospheric water vapor. It is based on the Differential Optical Absorption Spectroscopy (DOAS)-technique using high-resolution absorption spectra of solar radiation in the visible and near infrared spectral region. The investigations include theoretical aspects of the measurement process, simulations for optimizing instrumental parameters, design and construction of the spectrometer system, as well as validation of the technique by comparisons with independent methods. The first step was the implementation of a numerical radiative transfer model which simulates the process of molecular line absorption in the troposphere. It computes theoretical transmission functions of the atmosphere by calculating superposed individual transitions on a line-by-line basis. The line parameters of the vibrationrotational transitions were taken from the molecular database HITRAN. The model was used for determining the specifications of the spectrometer system, such as the optimum spectral intervals for the DOAS measurements. On the basis of these simulations a dedicated DOAS system was developed, which comprises a Sun tracking telescope with integrated premonochromator and a highresolution Echelle grating spectrometer called SAMOS (Solar Atmospheric MOnitoring Spectrometer). The spectrometer prototype is characterized by a high spectral resolution of better then 2 picometers over the entire measurable range and an integrated absolute wavelength calibration based on simultaneous measurements of neon reference spectra. The algorithm for processing SAMOS spectra is based on a least squares fit of the radiative transfer model to the measured spectra by adjusting the parameter for the precipitable water vapor (PW). First results revealed offsets between retrievals from different spectral intervals, implying significant errors in the HITRAN line parameters. Therefore line strength parameters were estimated using a dataset of radiosonde soundings and simultaneous SAMOS measurements, which greatly enhanced the redundancy of the retrievals. The new instrument was deployed in several field campaigns with collocated water vapor radiometers (WVR) and Global Positioning System (GPS) receivers, in which the feasibility of the solar spectrometry technique was proven. The comparison of SAMOS results with PW estimates from GPS data yielded a statistical agreement within 1 kg/m. However, systematic deviations were observed which are likely to arise from inherent effects of the GPS meteorology technique. The accuracy analysis of the solar spectrometry approach revealed that the largest fraction of retrieval error arises from uncertainties in the line parameters. The low sensitivity to model assumptions on meteorological profiles enables accurate retrievals of PW, but was found to render the possibility of deriving vertical humidity profiles from SAMOS spectra impracticable. The new technique can contribute to the validation and calibration of GPS water vapor estimates for meteorological applications. Numéro de notice : 13176 Affiliation des auteurs : non IGN Autre URL associée : http://dx.doi.org/10.3929/ethz-a-004039907 Thématique : IMAGERIE Nature : Thèse étrangère DOI : 10.3929/ethz-a-004039907 En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-62.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54901

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Code-barres	Cote	Support	Localisation	Section	Disponibilité
13176-02	35.45	Livre	Centre de documentation	Télédétection	Disponible
13176-01	35.45	Livre	Centre de documentation	Télédétection	Disponible