1Laboratory of Climate and Environmental Physics, Ural Federal University, Yekaterinburg, Russia
2Institute for Meteorology and Climate Research (IMK-ASF), Karlsruhe Institute of Technology, Karlsruhe, Germany
3Institut Pierre Simon Laplace, Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvette, France
4Atmosphere and Ocean Research Institute, University of Tokyo, Tokyo, Japan
5Alfred Wegener Institute for Polar and Marine Research, Bremen, Germany
6Institute of Environmental Physics, Bremen University, Bremerhaven, Germany
Received: 13 Nov 2013 – Discussion started: 14 Jan 2014
Abstract. This paper investigates the scientific value of retrieving H218O and HDO columns in addition to H216O columns from high-resolution ground-based near-infrared spectra. We present a set of refined H216O, H218O, and HDO spectral windows. The retrieved H216O, H218O, and HDO columns are used for an a posteriori calculation of columnar δD and δ18O. We estimate the uncertainties for the so-calculated columnar δD and δ18O values. These estimations include uncertainties due to the measurement noise, errors in the a priori data, and uncertainties in spectroscopic parameters. Time series of δ18O obtained from ground-based FTIR (Fourier transform infrared) spectra are presented for the first time.
Revised: 04 Jul 2014 – Accepted: 09 Jul 2014 – Published: 18 Aug 2014
For our study we use a full physics isotopic general circulation model (ECHAM5-wiso). We show that the full physics simulation of HDO and H218O can already be reasonably predicted from the H216O columns by a simple linear regression model (scatter values between full physics and linear regression simulations are 35 and 4‰ for HDO and H218O, respectively). We document that the columnar δD and δ18O values as calculated a posteriori from the retrievals of H216O, H218O, and HDO show a better agreement with the ECHAM5-wiso simulation than the δD and δ18O values as calculated from the H216O retrievals and the simple linear regression model. This suggests that the H218O and HDO column retrievals add complementary information to the H216O retrievals. However, these data have to be used carefully, because of the different vertical sensitivity of the H216O, H218O, and HDO columnar retrievals. Furthermore, we have to note that the retrievals use reanalysis humidity profiles as a priori input and the results are thus not independent of the reanalysis data.
Rokotyan, N. V., Zakharov, V. I., Gribanov, K. G., Schneider, M., Bréon, F.-M., Jouzel, J., Imasu, R., Werner, M., Butzin, M., Petri, C., Warneke, T., and Notholt, J.: A posteriori calculation of δ18O and δD in atmospheric water vapour from ground-based near-infrared FTIR retrievals of H216O, H218O, and HD16O, Atmos. Meas. Tech., 7, 2567-2580, doi:10.5194/amt-7-2567-2014, 2014.