International Collaboration in Chemistry: Development and application of a tuneable diode laser spectrometer for water isotope measurement and scientific studies during cloud simulation experiments in the AIDA chamber
Physik und Chemie der Atmosphäre
Zusammenfassung der Projektergebnisse
The project entitled “Improving understanding of ice nucleation and growth inhibition mechanisms via new isotopic tracer studies in the AIDA aerosol chamber (ISOCLOUD)”, by PTB, KIT and U Chicago (UoC), investigated isotopic H2O fractionation during dynamic cirrus cloud formation via adiabatic expansion cooling within the AIDA chamber. This required, new isotope specific in‐situ laser spectrometers and their adoption to AIDA, precise isotopic cloud spiking techniques in the AIDA cloud chamber, special pressure/temperature programs in AIDA to generate these ice clouds, and the development and application of isotopic fractionation models. PTB developed ‐ based on previous H216O laser hygrometers developed by PTB for AIDA ‐ a new, time‐multiplexed, multi‐isotope in‐situ laser hygrometer, which was adopted to AIDA using KIT’s opto‐mechanical support for an open long‐path cell in AIDA and a low temperature instrument housing. The PTB instrument, MC‐ISOPicT, simultaneously detects in the cloud (i.e. without gas sampling or calibration) absolute concentrations of H216O, H218O and HDO with a 1 s time resolution. New measurements by PTB improved the accuracy of the existing spectral data and thereby also the instrument accuracy. MC‐ISOPicT was validated via comparisons to VSMOV‐calibrated extractive instruments SIRI and REWAS by LiPhy and KIT and to a PTB reference laser hygrometer, SEALDH‐II, which is traceable to the German metrological humidity scale. With 227m absorption path MC‐ISOPicT enabled concentration precisions of 2.6 ppb for H216O, 1.4 ppb for HDO and 12 ppt for H218O. KIT hosted four IsoCloud campaigns at AIDA with a broad range of instruments, including the novel isotopic TDL instruments by PTB and UoC. Further extractive instruments from KIT and the associated project partner LiPhy measured total water and ice isotope fractionation. KIT developed a new device to selectively enhance the less abundant H2O isotopologues to enhance the signal quality needed for cloud studies down to 190 K. A wealth of further information was ensured via the inclusion of further AIDA facility instruments, e.g. dew point hygrometers, PCVI and TDL instruments like APeT / SP‐APicT (which were consistently evaluated by PTB). The combined information of all participating instruments allowed unprecedented studies of the isotopic water fractionation during ice cloud formation and led to a large and unique, isotope‐resolved cloud formation data set for various temperatures, pressures and isotopic conditions. This data set was made available to all the project partners for further analyses. NSF partner UoC led the extended analysis of the isotopic signatures during cloud formation and the development of microphysical models: E.g. based on the HDO data UoC showed a very good agreement with work from Merlivat/Nief (1967). Although the results could ‐ so far ‐ not discern diffusion‐limited‐ or equilibrium fractionation as limiting cases for the supersaturation observed in the upper troposphere, the ISOCLOUD project stands for an effective and successful transatlantic collaboration, which accomplished the development of novel, isotope‐selective in‐cloud hygrometers and the first direct measurement of water isotope fractionation factors and dynamics in ice clouds. This is of special relevance for the interpretation of hydrological isotope ratio signatures measured in the atmosphere, where no experimental validation of the transition dynamics exist. Furthermore, the work also created the basis for comparison and validation studies of isotope selective field instrumentation. The project partners thus rate this project very successful. All project objectives were reached or exceeded. The project led to a unique, well‐documented, very large, multi‐instrument and multi‐phase isotope resolved data set of dynamic cloud formation experiments often with a time resolution of seconds. These data are available to the scientific community for further evaluation.
Projektbezogene Publikationen (Auswahl)
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(2017) Laboratory measurements of HDO/H2O isotopic fractionation during ice deposition in simulated cirrus clouds. Proceedings of the National Academy of Sciences of the United States of America 114 (22) 5612–5617
Lamb, Kara D.; Clouser, Benjamin W.; Bolot, Maximilien; Sarkozy, Laszlo; Ebert, Volker; Saathoff, Harald; Möhler, Ottmar; Moyer, Elisabeth J.
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(2020) The Chicago Water Isotope Spectrometer (ChiWIS-lab): A tunable diode laser spectrometer for chamber-based measurements of water vapor isotopic evolution during cirrus formation. The Review of scientific instruments 91 (4) 045120
Sarkozy, Laszlo C.; Clouser, Benjamin W.; Lamb, Kara D.; Stutz, Eric J.; Saathoff, Harald; Möhler, Ottmar; Ebert, Volker; Moyer, Elisabeth J.
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Bestimmung von Wasserdampfpartialdrücken und Wasserisotopenverhältnissen mittels resonatorverstärkter Absorptionsspektroskopie ‐ Entwicklung von Software und Spektrometer sowie die Anwendung für die Atmosphärenforschung, PhD thesis, Karlsruhe Institute of Technology / University of Heidelberg, 2013
Habig, J.C.
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Development of an OF‐CEAS laser spectrometer for water vapor isotope measurements at low water concentrations, PhD thesis, Université de Grenoble and University of Groningen, 2014
Landsberg, F.J.
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Open‐path TDLAS for in‐situ detection of water isotopes in ice clouds down to 190 K, in Imaging and Applied Optics 2014, OSA Technical Digest (online) (Optical Society of America, 2014), ISBN: 978‐1‐55752‐308‐2, paper LTu3D.3
Kühnreich B., S.Wagner, J. C. Habig, H. Saathoff, E. J. Moyer, And V. Ebert
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(2015), Time‐multiplexed open‐path TDLAS spectrometer for dynamic, sampling‐free, interstitial H218O and H216O vapor detection in ice clouds, Appl. Phys. B., 119(1), 177‐187
Kühnreich, B., S. Wagner, J. C. Habig, O. Möhler, H. Saathoff, and V. Ebert
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In‐Situ Isotopic Water Vapor Measurements as a Tracer of Cold Cloud Microphysics, PhD thesis, University of Chicago, 2015
Lamb, K.D.
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Absorptionsspektroskopie zur isotopenaufgelösten in situ Bestimmung von Wasserdampf in Eiswolken, PhD thesis, Technische Universität Darmstadt, URN: 54893, Darmstadt, 2016
Kühnreich, B.
