Water vapour profiles by ground-based FTIR spectroscopy: study for an optimised retrieval and its validation

M. Schneider (1) , F. Hase (1) , T. Blumenstock (1)

1 IMK-ASF - Institut für Meteorologie und Klimaforschung - Atmosphärische Spurengase und Fernerkundung

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.

Domaines: Océan, Atmosphère

M. Schneider, F. Hase, T. Blumenstock. Water vapour profiles by ground-based FTIR spectroscopy: study for an optimised retrieval and its validation. Atmospheric Chemistry and Physics Discussions, 2005, 5 (5), pp.9493-9545. ⟨hal-00301825⟩