Development of a water vapor isotope ratio infrared spectrometer and application to measure atmospheric water in Antarctica
In recent years, the measurement of water isotopologues has become increasingly important for atmospheric research. Due to the influence of climatic conditions on the isotope ratios, the isotopic composition of water stored in the ice in Antarctica and the Arctic can be used as paleothermometers to...
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| Other Authors: | , , , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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HAL CCSD
2014
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| Subjects: | |
| Online Access: | https://theses.hal.science/tel-01369376 https://theses.hal.science/tel-01369376/document https://theses.hal.science/tel-01369376/file/LANDSBERG_2014_archivage.pdf |
| Summary: | In recent years, the measurement of water isotopologues has become increasingly important for atmospheric research. Due to the influence of climatic conditions on the isotope ratios, the isotopic composition of water stored in the ice in Antarctica and the Arctic can be used as paleothermometers to reconstruct past climate changes. The measurement of changes of the isotopic composition of water vapor in the atmosphere can be used to study the global hydrolocal cycle and to refine atmospheric circulation models.Whereas the conventional method for water isotope measurements, Isotope Ratio Mass Spectrometry (IRMS), is not adapted for in-situ continuous measurements of water vapor isotopes, the recent development of laser spectrometers offers a comparably easy and robust method to conduct in-the-field research with good time resolution. However, until now, most optical instruments require relative high humidity levels with water concentrations of at least several 1000 ppmv, which excludes measurements in some of the most interesting regions for water isotope research, such as the upper atmosphere and the central regions of Antarctica.In this work, we present a novel infrared laser spectrometer based on the technique OFCEAS, specifically designed to measure the four isotopologues H2_16O, H2_18O, H2_17O and HDO under very dry conditions, at water concentrations of some hundred to only tens of ppmv. The instrument developed during this thesis shows much higher measurement stability over time compared to previous OFCEAS instruments with optimum integration times of up to several hours and a very long effective path length of more than 30 km. At water concentrations around 80 ppmv, a precision of 0.8‰, 0.1‰ and 0.2‰ for d2H, d18O and d17O respectively could be achieved with an integration time of 30 to 60 min and at the optimum water concentration of ~650 ppmv, of 0.28‰, 0.02‰ and 0.07‰ respectively.An investigation of the overall performance of the instrument is presented and we specifically discuss the problem of a ... |
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