Articles | Volume 10, issue 3
Atmos. Meas. Tech., 10, 1111–1137, 2017

Special issue: Water vapour in the upper troposphere and middle atmosphere:...

Atmos. Meas. Tech., 10, 1111–1137, 2017
Research article
16 Mar 2017
Research article | 16 Mar 2017

The SPARC water vapour assessment II: comparison of annual, semi-annual and quasi-biennial variations in stratospheric and lower mesospheric water vapour observed from satellites

Stefan Lossow1, Farahnaz Khosrawi1, Gerald E. Nedoluha2, Faiza Azam3, Klaus Bramstedt3, John. P. Burrows3, Bianca M. Dinelli4, Patrick Eriksson5, Patrick J. Espy6, Maya García-Comas7, John C. Gille8,9, Michael Kiefer1, Stefan Noël3, Piera Raspollini10, William G. Read11, Karen H. Rosenlof12, Alexei Rozanov3, Christopher E. Sioris13, Gabriele P. Stiller1, Kaley A. Walker14, and Katja Weigel3 Stefan Lossow et al.
  • 1Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Hermann-von-Helmholtz-Platz 1, 76344 Leopoldshafen, Germany
  • 2Naval Research Laboratory, Remote Sensing Division, 4555 Overlook Avenue Southwest, Washington, DC 20375, USA
  • 3University of Bremen, Institute of Environmental Physics, Otto-Hahn-Allee 1, 28334 Bremen, Germany
  • 4Istituto di Scienze dell’Atmosfera e del Clima del Consiglio Nazionale delle Ricerche (ISAC-CNR), Via Gobetti, 101, 40129 Bologna, Italy
  • 5Chalmers University of Technology, Department of Earth and Space Sciences, Hörsalsvägen 11, 41296 Göteborg, Sweden
  • 6Norwegian University of Science and Technology, Department of Physics, Høgskoleringen 5, 7034 Trondheim, Norway
  • 7Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, 18008 Granada, Spain
  • 8National Center for Atmospheric Research, Atmospheric Chemistry Observations & Modeling Laboratory, P.O. Box 3000, Boulder, CO 80307-3000, USA
  • 9University of Colorado, Atmospheric and Oceanic Sciences, Boulder, CO 80309-0311, USA
  • 10Istituto di Fisica Applicata del Consiglio Nazionale delle Ricerche (IFAC-CNR), Via Madonna del Piano, 10, 50019 Sesto Fiorentino, Italy
  • 11Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
  • 12NOAA Earth System Research Laboratory, Global Monitoring Division, 325 Broadway, Boulder, CO 80305, USA
  • 13York University, Center for Research in Earth and Space Science, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada
  • 14University of Toronto, Department of Physics, 60 St. George Street, Toronto, Ontario M5S 1A7, Canada

Abstract. In the framework of the second SPARC (Stratosphere-troposphere Processes And their Role in Climate) water vapour assessment (WAVAS-II), the amplitudes and phases of the annual, semi-annual and quasi-biennial variation in stratospheric and lower mesospheric water were compared using 30 data sets from 13 different satellite instruments. These comparisons aimed to provide a comprehensive overview of the typical uncertainties in the observational database which can be considered in subsequent observational and modelling studies. For the amplitudes, a good agreement of their latitude and altitude distribution was found. Quantitatively there were differences in particular at high latitudes, close to the tropopause and in the lower mesosphere. In these regions, the standard deviation over all data sets typically exceeded 0.2 ppmv for the annual variation and 0.1 ppmv for the semi-annual and quasi-biennial variation. For the phase, larger differences between the data sets were found in the lower mesosphere. Generally the smallest phase uncertainties can be observed in regions where the amplitude of the variability is large. The standard deviations of the phases for all data sets were typically smaller than a month for the annual and semi-annual variation and smaller than 5 months for the quasi-biennial variation. The amplitude and phase differences among the data sets are caused by a combination of factors. In general, differences in the temporal variation of systematic errors and in the observational sampling play a dominant role. In addition, differences in the vertical resolution of the data, the considered time periods and influences of clouds, aerosols as well as non-local thermodynamic equilibrium (NLTE) effects cause differences between the individual data sets.