balloon-borne measurements; laser absorption spectroscopy; Wasserdampf; UT/LS; Hygrometer
Graf Manuel, Scheidegger Philipp, Kupferschmid André, Looser Herbert, Peter Thomas, Dirksen Ruud, Emmenegger Lukas, Tuzson Béla (2021), Compact and lightweight mid-infrared laser spectrometer for balloon-borne water vapor measurements in the UTLS, in Atmospheric Measurement Techniques
, 14(2), 1365-1378.
Tuzson Béla, Graf Manuel, Ravelid Jonas, Scheidegger Philipp, Kupferschmid André, Looser Herbert, Morales Randulph Paulo, Emmenegger Lukas (2020), A compact QCL spectrometer for mobile, high-precision methane sensing aboard drones, in Atmospheric Measurement Techniques
, 13(9), 4715-4726.
Liu Chang, Tuzson Béla, Scheidegger Philipp, Looser Herbert, Bereiter Bernhard, Graf Manuel, Hundt Morten, Aseev Oleg, Maas Deran, Emmenegger Lukas (2018), Laser driving and data processing concept for mobile trace gas sensing: Design and implementation, in Review of Scientific Instruments
, 89(6), 065107-065107.
Graf Manuel, Emmenegger Lukas, Tuzson Béla (2018), Compact, circular, and optically stable multipass cell for mobile laser absorption spectroscopy, in Optics Letters
, 43(11), 2434-2434.
Emmenegger Lukas, Stanicki Badrudin, Graf Manuel, Scheidegger Philipp, Hundt Morten, Faist Jérôme, Kapsalidis Filippos, Looser Herbert, Shahmohammadi Mehran, Tuzson Béla QCL absorption spectroscopy for lightweight and multi-species environmental applications, (2018), QCL absorption spectroscopy for lightweight and multi-species environmental applications
, OSA Publishing, USA.
Graf Manuel, Looser Herbert, Emmenegger Lukas, Tuzson Béla (2017), Beam folding analysis and optimization of mask-enhanced toroidal multipass cells, in Optics Letters
, 42(16), 3137-3137.
Accurate and reliable measurements of water vapor in the Upper Troposphere and Lower Stratosphere (UT/LS) are needed for a wide range of applications, such as forecast modeling, radiative transfer calculations and climate trend studies. Furthermore, water vapor plays an important role in stratospheric dehydration, troposphere-stratosphere exchange processes, and the formation of cirrus clouds. At present, however, UT/LS water vapor distributions are not well understood.In situ humidity measurements in the UT/LS can be performed with hygrometers using a large variety of techniques, such as chilled mirrors, the Lyman-a technique, and tunable diode laser spectroscopy. Recent field campaigns have provided clear evidence for large deviations between hygrometers, rendering them questionable for useful determination of relative humidity at lower water vapor content (few ppm), such as found in the LS. Intercomparisons of state-of-the-art and prototype hygrometers in aerosol and cloud chambers under controlled conditions have further revealed serious discrepancies, neither explaining the errors fully nor suggesting a solution to the problem.Laser absorption spectroscopy in the mid-infrared is a rapidly evolving technique that combines very high selectivity, sensitivity and time response. In the frame of this project we propose to develop a lightweight quantum cascade laser based spectroscopic setup for measuring atmospheric H2O in the UT/LS. Our aim is to explore new limits for sensitivity and precision, and to show the feasibility of in situ H2O measurements by laser absorption spectroscopy onboard a meteorological balloon. The ultimate goal is to measure water vapor with better than 4 % accuracy at 1 s time resolution for mixing rations of a few parts-per-million (ppm), i.e. even under stratospheric conditions of up to 20 km altitude, at a temperature of about 180 K and a pressure below 60 hPa.In order to achieve this ambitious goal, we propose a direct absorption approach based on a novel, open ring-shaped multipass-cell design, a mid-infrared quantum cascade laser, our intermittent low-dissipation laser driving electronics, and FPGA based data acquisition. This combination offers an outstanding and unique solution to obtain the necessary signal-to-noise ratio required for water vapor measurements in the UT/LS.The project is based on the work of a PhD student and the strong competence in laser spectroscopy and trace gas monitoring of Empa. For instrument validation, inter-laboratory and in-flight comparisons with established chilled mirror hygrometers will be performed in collaboration with IACETH and MeteoSwiss.