Afchine, Armin

Barthel, Jochen

Buchholz, Bernhard

Ebert, Volker

Kallweit, Sören

Klein, Alexander

Klostermann, Tim

Krämer, Martina

Schiller, C.

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Simultaneous gas-phase and total water detection for airborne applications with a multi-channel TDL spectrometer at 1.4 µm and 2.6 µm

Geophysical Research AbstractsVol. 15, EGU2013-7311-3, 2013EGU General Assembly 2013© Author(s) 2013. CC Attribution 3.0 License.Simultaneous gas-phase and total water detection for airborneapplications with a multi-channel TDL spectrometer at 1.4 µm and 2.6 µmBernhard Buchholz (1,2), Armin Afchine (3), Alexander Klein (1), Jochen Barthel (3), Sören Kallweit (1), TimKlostermann (3), Martina Krämer (3), Cornelius Schiller (3), Volker Ebert (1,2)(1) Physikalisch-Technische Bundesanstalt Braunschweig, Germany, (2) Center of Smart Interfaces, Technische UniversitätDarmstadt, Germany, (3) Forschungszentrum Jülich, IEK-7, GermanyWater vapor measurements especially within clouds are difficult, in particular due to numerous instrument-specificlimitations in precision, time resolution and accuracy. Notably the quantification of the ice and gas-phase wa-ter content in cirrus clouds, which play an important role in the global climate system, require new high-speedhygrometers concepts which are capable of resolving large water vapor gradients. Previously we demonstrateda stationary concept of a Tunable Diode Laser Absorption Spectroscopy (TDLAS)-based quantification of theice/liquid water by independent, but simultaneous measurements of A) the gas-phase water in an open-path con-figuration (optical-path 125 m) and B) the total water in an extractive version with a closed cell (30 m path) afterevaporating the condensed water [1]. In this case we used laboratory TDLAS instrumentation in combination witha long absorption paths and applied those to the AIDA cloud camber [2].Recently we developed an advanced, miniature version of the concept, suitable for mobile field applicationsand in particular for use on aircrafts. First tests of our new, fiber-coupled open-path TDLAS cell [3] for air-borne applications were combined with the experiences of our extractive SEALDH instruments [4] and led to anew, multi-channel, “multi-phase TDL-hygrometer” called “HAI” (“Hygrometer for Atmospheric Investigations”).HAI, which is explicitly designed for the new German HALO (High Altitude and Long Range Research Aircraft)airplane, provides a similar, but improved functionality like the stationary, multi-phase TDLAS developed forAIDA. However HAI comes in a much more compact, six height units, 30 kg, electronics rack for the main unitand with a new, completely fiber-coupled, compact, 21 kg, dual-wavelength open-path TDL-cell which is placedin the aircraft’s skin. HAI is much more complex and versatile than the AIDA precursor and can be seen as com-prised of four TDL-spectrometers, as it simultaneously measures with two independent wavelengths (1.4 µm fortroposphere and 2.6 µm for UT/LS to permit full coverage of water vapor concentrations from ground level to thestratosphere) both of which are applied to two measurement scenarios: A) in two independent extractive, closedcells (1.5 m path, 300 ccm cell volume) for redundant total water measurements at 1.4 and 2.6 µm and B) in adual-wavelength open path cell (4.3 m path length) for a selective gas phase water detection. All HAI channels,but the 2.6 µm closed cell, are fibred-coupled. Depending on the sampling inlet (forward direction, ram pressureborrowed) we achieve in the closed cells a flow of 7 slm at 120 hPa which leads with a bulk flow assumption to agas exchange time of 0.3 sec. Both lasers are synchronized and wavelength tuned at repetition frequencies of upto 1 kHz depending on the spatial resolution needed. HAI runs autonomous [5] allowing almost maintenance-freeoperation even in harsh environments. HAI is further combined with our long-term experience in TDLAS dataevaluation [6] especially in rapidly changing and disturbed processes [7], [8] which leads to a highly precise, longterm stable, fast, accurate, calibration-free, interference resistant hygrometer which can help to clarify several im-portant issues - both from a technical perspective (e.g. influence of sampling system) as well as from a scientificview (e.g. determination ice-content of cirrus clouds).In the presentation we will discuss HAI’s novel setup, its performance during the first tests, and show results fromthe first successful flights on HALO during the TACTS and EMSVAL campaigns in 2012.The HAI development was funded by DFG within the HALO-SPP 1294 and via internal funds from FZJ.-[1] B. J. Murray, T. W. Wilson, S. Dobbie, Z. Cui, S. M. R. K. Al-Jumur, O. Möhler, M. Schnaiter, R. Wagner, S.Benz, M. Niemand, H. Saathoff, V. Ebert, S. Wagner, and B. Kärcher, “Heterogeneous nucleation of ice particleson glassy aerosols under cirrus conditions,” Nature Geoscience, vol. 3, no. 4, pp. 233–237, Mar. 2010.[2] V. Ebert, C. Lauer, H. Saathoff, S. Hunsmann, and S. Wagner, “Simultaneous, absolute gas-phase and totalwater detection during cloud formation studies in the AIDA chamber using a dual 1.37 µm TDL-Spectrometer,”Geophysical Research Abstracts, vol. 10, pp. 1–2, 2008.[3] T. Klostermann, Entwicklung und Erprobung des Hygrometer for Atmospheric Investigations, PhD Thesis,Universität Wuppertal, 2011, p. 118[4] B. Buchholz, B. Kühnreich, H. G. J. Smit, and V. Ebert, “Validation of an extractive, airborne, compact TDLspectrometer for atmospheric humidity sensing by blind intercomparison,” Applied Physics B, Sep. 2012. DOI:10.1007/s00340-012-5143-1[5] B. Buchholz, “Neue Hard- und Softwareentwicklungen für autonome, kompakte und leichte Feld-Diodenlaserspektrometer,” Diploma thesis, Universität Heidelberg, 2010.[6] V. Ebert and J. Wolfrum, “Absorption spectroscopy,” in OPTICAL MEASUREMENTS-Techniques and Appli-cations, ed. F. Mayinger, Springer, 1994, pp. 273–312.[7] C. Schulz, A. Dreizler, V. Ebert, and J. Wolfrum, “Combustion Diagnostics,” in Handbook of ExperimentalFluid Mechanics, C. Tropea, A. L. Yarin, and J. F. Foss, Eds. Heidelberg: Springer Berlin Heidelberg, 2007, pp.1241–1316.[8] V. Ebert, T. Fernholz, C. Giesemann, H. Pitz, H. Teichert, J. Wolfrum, and H. Jaritz, “Simultaneous diode-laser-based in situ detection of multiple species and temperature in a gas-fired power plant,” Proc. Combust. Inst., 28, 1,pp. 423–430, 2000.

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Simultaneous gas-phase and total water detection for airborne applications with a multi-channel TDL spectrometer at 1.4 µm and 2.6 µm

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