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Atmos. Chem. Phys. Discuss., 5, 9493-9545, 2005
www.atmos-chem-phys-discuss.net/5/9493/2005/ doi:10.5194/acpd-5-9493-2005 © Author(s) 2005. This work is licensed under a Creative Commons License. |
Water vapour profiles by ground-based FTIR spectroscopy: study for an optimised retrieval and its validation
IMK-ASF, Forschungszentrum Karlsruhe and Universität Karlsruhe, Germany
Abstract. The sensitivity of ground-based instruments measuring in the infrared with respect to tropospheric water vapour content is generally limited to the lower and middle troposphere. The large vertical gradients and variabilities avoid a better sensitivity for the upper troposphere/lower stratosphere region. In this work an optimised retrieval is presented and it is demonstrated that compared to a commonly applied method, it widely improves the performance of the FTIR technique with respect to upper tropospheric water vapour. Within a realistic error scenario it is estimated that the optimised method reduces the upper tropospheric uncertainties by about 25–30%, leading to a noise to signal ratio of 50%. The reasons for this improvement and the possible deficiencies of the method are discussed. The estimations are confirmed by a comparison of retrieval results based on real FTIR measurements with coinciding measurements of synoptical meteorological radiosondes.
Citation: Schneider, M., Hase, F., and Blumenstock, T.: Water vapour profiles by ground-based FTIR spectroscopy: study for an optimised retrieval and its validation, Atmos. Chem. Phys. Discuss., 5, 9493-9545, doi:10.5194/acpd-5-9493-2005, 2005.