The FIRMOS Zugspitze campaign: Level 2 retrievals in clear sky

FIRMOS (Far-Infrared Radiation Mobile Observation System) is a Fourier transform spectrometer covering the range from 100 to 1000 cm-1, developed to support the preparation of the satellite mission FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) planned in 2025/2026 (Earth Explorer 9 - ESA). FIRMOS was deployed at the Alpine observatory of Mt. Zugspitze, in the South of Germany, at about 3000 m a.s.l. for 2 months (December 2018 and January-February 2019). In January-February 2019, FIRMOS acquired about 600 measurements of the downwelling spectral radiance in clear sky condition. In this presentation, we present results of the retrieval of the water vapour and temperature profiles obtained from Level 2 analysis of the FIRMOS measurements in clear sky condition. Dedicated and coincident measurements allowed us to perform a comparison with integrated water vapour obtained from E-AERI (Extended-range Atmospheric Emitted Radiance Interferometer) at Zugspitze summit station and with radio-sounding launched at Garmisch-Partenkirchen. Comparisons with further independent information are also shown. Acknowledgments. The authors gratefully acknowledge the funding support by the European Space Agency with the FIRMOS project (ESA-ESTEC Contract No. 4000123691/18/NL/LF) and the Italian Space Agency with the research projects SCIEF (Italian acronym of Development of the National Competences for the FORUM experiment - ASI contract No. 2016-010-U.0)