10.1117/2.1201306.004940 Measuring atmospheric water isotopes in Western Siberia Konstantin Gribanov and Nikita Rokotyan A new observation station makes continuous measurements of water isotopes for climate studies, using several remotely-operated spectrom- eters and meteorological instruments. Stable water isotope concentrations can be used as tracers of the atmospheric water cycle. 1 Differences in molecular mass of the isotopes cause them to fractionate during evaporation and condensation processes and, as such, they can record air mass history. The relative concentrations of carbon isotopes in methane (CH 4 ) and carbon dioxide (CO 2 ), i.e., 13 CH 4 , 12 CH 4 , 13 CO 2 , and 12 CO 2 , in the atmosphere provides information about the sources of these greenhouse gases and can be used to study climate change. The atmospheric transmittance of solar radiation can be measured in the near-IR spectral region. Instruments that make such measurements with high-spectral resolution enable specific features in the spectrum, which are characteristic to different atmospheric isotopologues (chemical species that differ only in their isotopic composition), to be identified. These observations are used to calculate the total concentration of the gases in the atmospheric column. We have been developing new methods for retrieving the ratios of hydrogen deuterium oxide (HDO) to water (H 2 O), 2 13 CH 4 to 12 CH 4 , and 13 CO 2 to 12 CO 2 from ground-based Fourier transform IR spectroscopy (FTIR) measurements. 3 Ground-based FTIR measurements are made at the Ural Atmospheric Fourier Station (UAFS) simultaneously with direct wavelength-scanned cavity ring-down spectroscopy (WS-CRDS) measurements of water isotopologues, and with meteorological parameters. By combining these measurements with an atmospheric general circulation model—such as ECHAM5-wiso 4 —the results from several different techniques can be compared. 5 The UAFS site for atmospheric observations is located at the Kourovka astronomical observatory (57.038 ◦ N, 59.545 ◦ E, 300m above sea level), 80km northwest of Yekaterinburg, Russia (see Figures 1 and 2). UAFS began operations in 2009 and is Figure 1. Map of the Climate and Environmental Physics Laboratory target region in Western Siberia. Red star: Ural Atmospheric Fourier Station (UAFS) near Kourovka. Red circle: Yekaterinburg. White star: Planned observation site at Labytnangi. maintained by the Climate and Environmental Physics Labora- tory (CEPL) of the Institute of Natural Sciences. The CEPL was created to work on a project entitled ”Impact of climate change on water and carbon cycles of melting permafrost of Siberia” and is a separate subdivision of the Ural Federal University. It includes three actively interacting sections: the remote sensing, surface measurements and field research, and modeling groups. UAFS is equipped with a Bruker IFS-124M high-spectral resolution FTIR spectrometer with a spectral range of 420–25000cm 1 . The spectrometer is connected to an A547N automated solar tracker, with a resolution of 0.0035cm 1 , that is mounted on the roof of the working pavilion. The tracker directs solar radiation to the spectrometer aperture via a sys- tem of gold-coated mirrors. We last upgraded the spectrometer at the beginning of 2013. The UAFS site is also equipped with a Picarro L2130-i WS-CRDS instrument and a Gill Instruments MetPak-II meteorological station. We are able to make continu- ous measurements of water isotopes (H 16 2 O, HD 16 O, and H 18 2 O) with the WS-CRDS. We obtain continuous temperature, humid- ity, atmospheric pressure, and wind direction data from the Continued on next page