Articles | Volume 5, issue 12
Atmos. Meas. Tech., 5, 3007–3027, 2012
Atmos. Meas. Tech., 5, 3007–3027, 2012

Research article 05 Dec 2012

Research article | 05 Dec 2012

Ground-based remote sensing of tropospheric water vapour isotopologues within the project MUSICA

M. Schneider1,2, S. Barthlott1, F. Hase1, Y. González2, K. Yoshimura3, O. E. García2, E. Sepúlveda2,4, A. Gomez-Pelaez2, M. Gisi1, R. Kohlhepp1, S. Dohe1, T. Blumenstock1, A. Wiegele1, E. Christner1, K. Strong5, D. Weaver5, M. Palm6, N. M. Deutscher6,8, T. Warneke6, J. Notholt6, B. Lejeune7, P. Demoulin7, N. Jones8, D. W. T. Griffith8, D. Smale9, and J. Robinson9 M. Schneider et al.
  • 1Institute for Meteorology and Climate Research (IMK-ASF), Karlsruhe Institute of Technology (KIT), Germany
  • 2Izaña Atmospheric Research Centre (IARC), Agencia Estatal de Meteorología (AEMET), Spain
  • 3University of Tokyo, Tokyo, Japan
  • 4Laguna University, Tenerife, Spain
  • 5Department of Physics, University of Toronto, Toronto, Ontario, Canada
  • 6Institute of Environmental Physics, University of Bremen, Bremen, Germany
  • 7Institute of Astrophysics and Geophysics, University of Liège, Liège, Belgium
  • 8Centre for Atmospheric Chemistry, University of Wollongong, Wollongong, New South Wales, Australia
  • 9National Institute of Water and Atmospheric Research, Lauder, New Zealand

Abstract. Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water), long-term tropospheric water vapour isotopologue data records are provided for ten globally distributed ground-based mid-infrared remote sensing stations of the NDACC (Network for the Detection of Atmospheric Composition Change). We present a new method allowing for an extensive and straightforward characterisation of the complex nature of such isotopologue remote sensing datasets. We demonstrate that the MUSICA humidity profiles are representative for most of the troposphere with a vertical resolution ranging from about 2 km (in the lower troposphere) to 8 km (in the upper troposphere) and with an estimated precision of better than 10%. We find that the sensitivity with respect to the isotopologue composition is limited to the lower and middle troposphere, whereby we estimate a precision of about 30‰ for the ratio between the two isotopologues HD16O and H216O. The measurement noise, the applied atmospheric temperature profiles, the uncertainty in the spectral baseline, and the cross-dependence on humidity are the leading error sources. We introduce an a posteriori correction method of the cross-dependence on humidity, and we recommend applying it to isotopologue ratio remote sensing datasets in general. In addition, we present mid-infrared CO2 retrievals and use them for demonstrating the MUSICA network-wide data consistency. In order to indicate the potential of long-term isotopologue remote sensing data if provided with a well-documented quality, we present a climatology and compare it to simulations of an isotope incorporated AGCM (Atmospheric General Circulation Model). We identify differences in the multi-year mean and seasonal cycles that significantly exceed the estimated errors, thereby indicating deficits in the modeled atmospheric water cycle.