Session AS5.13

[Programme]

AS5.13 | Advanced Spectroscopic Measurement Techniques and Applications for Atmospheric Science

Advanced Spectroscopic Measurement Techniques and Applications for Atmospheric Science

Convener: Weidong Chen | Co-conveners: Dean Venables, J. Houston Miller, Weixiong Zhao, Tobias D. SchmittECSECS

Orals

| Thu, 01 May, 16:15–18:00 (CEST)

Room M1

Posters on site

| Attendance Thu, 01 May, 14:00–15:45 (CEST) | Display Thu, 01 May, 14:00–18:00

Hall X5

Instrumentation and its development play a key role in advancing research, providing state-of-the-art tools to address open scientific questions. Over the last several decades, atmospheric environmental monitoring has benefited from novel spectroscopic measurement techniques that arose from breakthroughs in photonic technologies from the UV to THz spectral regions. These advances open new research avenues for observation of spatial and long-term trends in the concentration and optical properties of atmospheric constituents, and for studying atmospheric processes in laboratories and atmospheric simulation chambers. These advances are vital for expanding our insight into atmospheric composition and processes, and ultimately their impacts on air quality and global climate change.
The upcoming session of "Advanced Spectroscopic Measurement Techniques and Applications for Atmospheric Science" focuses on the latest developments and advances in a broad range of spectroscopic instrumentation and technologies, and their use in a variety of atmospheric applications. It aims to be a platform for sharing information on the state-of-the-art and emerging developments for atmospheric sensing. This interdis¬ciplinary forum aims to foster discussion among experimentalists, atmospheric scientists, and development engineers. It is also an opportunity for R&D and analytical equipment companies to evaluate the capabilities of new instrumentation and techniques.
Topics for presentation include developments, demonstrations and applications of novel spectroscopic methods and instruments dedicated to measuring atmospheric aerosols, isotopologues, greenhouse gases and other trace gases, as well as associated atmospheric meteorological parameters such as temperature, wind speed, humidity, etc. Studies of vertical concentration profiles and flux measurements are all welcome when the instrumentation is a focus of the work. Spectroscopic methods could include high sensitivity and selectivity spectroscopy (such as dual-comb spectroscopy, cavity-enhanced absorption/Raman spectroscopies, photoacoustic & photothermal spectroscopy and other spectroscopic methods), low-cost optical sensors, heterodyne radiometry and imaging spectroscopy. Applications include laboratory demonstration, ground and airborne platforms (UAV/drone, balloon, aircraft) observations, smog chamber studies. Approaches using new spectral data analysis tools (including machine learning) are encouraged.

Session assets

Session materials

Orals: Thu, 1 May | Room M1

Chairpersons: J. Houston Miller, Tobias D. Schmitt, Weixiong Zhao

16:15–16:20

5-minute convener introduction

16:20–16:30

EGU25-13660

ECS

On-site presentation

A compact light weight instrument for in situ detection of I2 in the marine boundary layer

Shogo Saito, Caroline Womack, Steven Brown, and Albert Ruth

The release of molecular iodine (I₂) from the oceans into the atmosphere has been recognized to correlate strongly with ozone depletion events and aerosol formation in the marine boundary layer [1,2]. The detailed mechanisms and dominant sources leading to the observed concentrations of I₂ and IO in the marine troposphere are still under investigation. One prime source of I₂ are brown macro-algae (kelp) such as Laminaria digitata, which release molecular iodine when under oxidative stress [3].

In order to further advance the understanding of I₂ exchange processes between the sea and atmosphere near the coast, it is essential to map the spatial and temporal distribution of I₂ over the shoreline. For that purpose we developed a low power (~20 W), compact, and light weight (~4 kg) instrument for the deployment in field trials on mobile platforms, including unmanned aerial vehicles. The instrument uses incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) [4] for I₂ detection, with a molecule-specific 3𝜎 detection limits of 48 pptv in 1 s, as demonstrated under laboratory conditions.

In this presentation, we outline the mechanical, optical, and electronic design of the instrument and discuss its general engineering features. Laboratory measurements of I₂ emitted by Laminaria digitata will be presented together with future applications and envisaged field deployments of the instrument.

Acknowledgement: This work is supported by Research Ireland (21/FFP-A-8973, AtmoTrace)

[1] A. Saiz-Lopez, J.M.C. Plane, Novel iodine chemistry in the marine boundary layer, Geophys. Res. Lett. 31, L04112 (2004).

[2] G. McFiggans et al., Direct evidence for coastal iodine particles from Laminaria macroalgae - linkage to emissions of molecular iodine, Atmos. Chem. Phys. 4, 701–713 (2004).

[3] S. Dixneuf et al., The time dependence of molecular iodine emission from Laminaria digitata, Atm. Chem. Phys. 9, 823–829 (2009).

[4] S.E. Fiedler et al. Incoherent broad-band cavity-enhanced absorption spectroscopy, Chem. Phys. Lett. 371, 284–294 (2003).

Key words: Marine boundary layer, iodine I₂, iodine oxide IO, macro-algae, cavity enhanced absorption spectroscopy.

How to cite: Saito, S., Womack, C., Brown, S., and Ruth, A.: A compact light weight instrument for in situ detection of I2 in the marine boundary layer, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13660, https://doi.org/10.5194/egusphere-egu25-13660, 2025.

16:30–16:40

EGU25-15173

ECS

On-site presentation

Atomic Oxygen and Temperature Retrieval in the MLT region by Terahertz Heterodyne Measurements from a Satellite: Single vs. Dual-frequency Scenarios

Peder Bagge Hansen, Martin Wienold, and Heinz-Wilhelm Hübers

Atomic oxygen is a key component of the mesosphere and lower thermosphere (MLT) in Earth's atmosphere. It plays a crucial role in the energy balance and chemical processes within the MLT region, along with the temperature.

The Keystone mission, which is an upper-atmosphere limb-sounding satellite initiative, has entered its phase-0 study [1]. Operating from a low Earth orbit, Keystone will scan the atmosphere at varying tangential heights to measure several atmospheric gases. Most notably, Keystone aims to observe atomic oxygen through its terahertz (THz) fine-structure transitions at 2.1 THz and 4.7 THz. These transitions, being in local thermodynamic equilibrium (LTE), enable the retrieval of vertical atomic oxygen concentration profiles without reliance on photochemical models, but requiring only the local temperature.

The fine-structure transitions of atomic oxygen can be spectrally resolved using heterodyne spectroscopy technology [2,3]. Temperature can then be derived from either the Doppler broadening of these transitions or from the relative intensities of the two transitions, as they originate from distinct upper electronic levels (0.028 eV for the 2.1 THz transition and 0.020 eV for the 4.7 THz transition).

This study evaluates the retrieval uncertainties in temperature and atomic oxygen density for a limb sounding satellite mission such as Keystone. We use the methodology also presented in [4] to compare scenarios with two THz channels measuring both the 2.1 THz and 4.7 THz transitions against those measuring only one transition. For two channels with similar noise levels we find that measuring both transitions improve the precision in atomic oxygen concentration beyond what is gained from the increased signal by using two detectors.

[1] D. Gerber, webpage, https://ceoi.ac.uk/eo-missions/earth-explorer-11/keystone/, visited 14th January 2025.

[2] Richter, H., et al., Commun Earth Environ 2, 19 (2021).

[3] Wienold, M., et al., IEEE Transactions on Terahertz Science and Technology, vol. 14, no. 3 (2024).

[4] Hansen, P., et al., EGU General Assembly 2024, Vienna, Austria, (2024).

How to cite: Hansen, P. B., Wienold, M., and Hübers, H.-W.: Atomic Oxygen and Temperature Retrieval in the MLT region by Terahertz Heterodyne Measurements from a Satellite: Single vs. Dual-frequency Scenarios, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15173, https://doi.org/10.5194/egusphere-egu25-15173, 2025.

16:40–16:50

EGU25-15608

On-site presentation

Quartz-Enhanced Photoacoustic Spectroscopy for Environmental Monitoring

Pietro Patimisco, Andrea Zifarelli, Raffaele De Palo, Mariagrazia Olivieri, Angelo Sampaolo, and Vincenzo Spagnolo

Air pollution is a critical global issue, contributing to over 4.2 million deaths annually due to stroke, heart disease, lung cancer, and chronic respiratory diseases. It also poses significant economic and social challenges, including increased healthcare costs and reduced productivity. The need for real-time, high-resolution air quality monitoring is essential to minimize public exposure, particularly for vulnerable populations. However, existing ambient pollutant detectors are bulky and impractical for widespread deployment, and current electrochemical sensors lack the stability and sensitivity required for regulatory compliance.

In this context, we report the results obtained within the European Project PASSEPARTOUT in advancing the development of miniature, hyperspectral optical sensors based on Quartz Enhanced Photoacoustic Spectroscopy (QEPAS). QEPAS is trace gas optical detection technique that exploits the photoacoustic effect occurring in a gas sample when a modulated, resonant light is absorbed by the target analytes. A weakly damped propagating acoustic (pressure) wave with wavelengths in the centimeter range is generated in the proximity of the exciting light beam. In QEPAS, these sound waves are detected by a spectrophone, composed of a quartz-tuning fork (QTF) transducer and a pair of millimeter-size resonator tubes, aligned on both sides of the QTF.

Eight different air pollutants, namely CH₄, NO₂, CO₂, N₂O, CO, NO, SO₂ and NH₃ have been detected with the same acoustic detection module (containing the spectrophone) and interchangeable laser sources, to prove the modularity of the technique as well as the adaptability to different lasers. Each gas species was detected with an ultimate detection limit well below their typical natural abundance in air even with a signal integration time as low as 0.1 s.

Two significant advancements have also been achieved. The first involves the development of a portable, field-deployable QEPAS sensor that eliminates the need for free-space optical components, thereby increasing the mechanical stability and robustness of the system. By integrating a single-mode fiber to guide the laser beam into the spectrophone, the sensor achieves enhanced flexibility and ease of deployment. The second innovation consists of a custom-designed three-wavelength laser module, combining three quantum cascade lasers (QCLs) into a single collimated beam, further extends the sensor’s capabilities for multi-gas detection with a single sensor architecture.

These advancements pave the way for the deployment of mobile, high-precision air quality monitoring systems that are scalable, adaptable, and capable of providing real-time data for regulatory compliance and public health protection.

How to cite: Patimisco, P., Zifarelli, A., De Palo, R., Olivieri, M., Sampaolo, A., and Spagnolo, V.: Quartz-Enhanced Photoacoustic Spectroscopy for Environmental Monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15608, https://doi.org/10.5194/egusphere-egu25-15608, 2025.

16:50–17:00

EGU25-17118

On-site presentation

Advances in lightweight laser-based analyzers for flying platforms

Béla Tuzson, Lorenz Heilmann, Simone Brunamonti, Philipp Scheidegger, André Kupferschmid, Alex Weitnauer, and Lukas Emmenegger

Laser absorption spectroscopy is a widely adopted technique for high-precision trace-gas analysis across a broad range of applications. However, commercial instruments remain too bulky for deployment on flying platforms, such as UAVs or balloons. The key challenge thus remains reducing their size without compromosing their analytical performance.

In this study, we address this challenge and showcase our ongoing developments that have enabled the creation of highly compact mid-infrared trace-gase analyzers. Key innovations include: i) a rapid frequency sweep of the laser using an intermittent continuous wave (icw) driving scheme [1], which reduces the footprint and improves energy and heat management efficiency, ii) a fully monolithic segmented circular multipass cell design [2] that overcomes the size and weight limitations of traditional absorption cells, and iii) an FPGA-based data acquisition system capable of processing large volumes of data in real-time with bandwidths up to 250 MB/s [3].

By combining these groundbreaking developments, we have developed fully autonomous devices that excel in robustness, compactness, rigidity, and lightweight design. Their exceptional in-flight performance is demonstrated through selected field deployments on UAVs and balloons [3-5]. Ongoing developments include multi-species trace-gases detection to monitor ship emissions. This requires a fundamental reconception of the circular multipass cell to increase its optical path length by an order of magnitude.

The versatility and ruggedness of these lightweight and low-footprint spectrometers unlocks new opportunities for applications requiring high spatio-temporal resolution, such as urban or industrial site monitoring and upper atmosphere observation.

References:

[1] C. Liu et al., Rev. Sci. Instr. 89, 065107, 2018.

[2] M. Graf et al., Opt. Lett. 43, 2434-2437, 2018.

[3] B. Tuzson et al., Atmos. Meas. Tech., 13(9), 4715-4726, 2020.

[4] M. Graf et al., Atmos. Meas. Tech., 14(2), 1365-1378, 2021.

[5] Brunamonti et al., Atmos. Meas. Tech., 16, 4391–4407, 2023.

How to cite: Tuzson, B., Heilmann, L., Brunamonti, S., Scheidegger, P., Kupferschmid, A., Weitnauer, A., and Emmenegger, L.: Advances in lightweight laser-based analyzers for flying platforms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17118, https://doi.org/10.5194/egusphere-egu25-17118, 2025.

17:00–17:10

EGU25-18041

ECS

On-site presentation

Real time monitoring of N2O and CO emissions from vehicles using a quartz-enhanced photoacoustic sensor

Mariagrazia Olivieri, Andrea Zifarelli, Angelo Sampaolo, Vincenzo Spagnolo, and Pietro Patimisco

Greenhouse gases represent a crucial component of Earth's atmospheric system, playing a fundamental role in maintaining the planet's heat balance through their ability to absorb and emit infrared radiation. Anthropogenic activities have increased the atmospheric concentration of these gases, leading to enhanced global warming effects. The primary greenhouse gases include carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and water vapor (H₂O). Among the other pollutants, carbon monoxide (CO) stands out as one of the most hazardous for human health. In urban areas, vehicle emissions represent the primary source of CO, produced through incomplete fuel combustion, with concentrations significantly higher than in unpolluted areas (∼50 ppb). Furthermore, vehicles emissions, particularly from those equipped with catalytic converters, partially contribute to the global atmospheric N2O budget, whose atmospheric concentration is ~300 ppb. The deployment of portable and reliable sensors to monitor these emissions is crucial for understanding their sources, assessing their impact, and developing effective mitigation strategies.
Quartz Enhanced Photoacoustic Spectroscopy (QEPAS) sensors offer an effective solution for monitoring air pollutants, providing high selectivity and sensitivity, compact dimensions, and rapid response times. Photoacoustic (PAS) basic principle consists in detecting sound waves induced by gas non-radiative energy relaxation as consequence of infrared modulated light absorption. QEPAS represents an evolution of the PAS approach and exploits a quartz tuning fork (QTF) to transduce the acoustic wave into an electric signal. Mid-IR Quantum Cascade Lasers (QCLs) have been employed as light source in QEPAS-based sensor to target the absorption bands of both N2O and CO.
Here we report on the realization of a QEPAS-based system employing a QCL with a central emission wavelength at 4.61 μm and a T-shaped QTF coupled with a pair of acoustic resonator tubes to amplify the sound wave. A ~1 min ramp was added to the fast laser modulation to scan the 2190.6-2188.7 cm-1 spectral range, where well-resolved absorption features of N2O and CO were selected. Laboratory calibrations with certified gas cylinders demonstrated the sensor's ability to detect N₂O and CO at hundreds and tens of ppb level, respectively, at a working pressure of 300 Torr and an integration time of 100 ms. We demonstrated the sensor capability to continuously monitor the QEPAS signal of the two gases both in indoor and outdoor environments. Indoor measurements were carried out over several days by sampling air inside the laboratory, while outdoor measurements took place in a university parking area in Bari to continuously monitor vehicle emissions. During spectral scans, the laser power, the sample temperature and its water vapor content was continuously measured, to eventually compensate for their influence on QEPAS signal. The resulting performances demonstrated its applicability for the realization of a compact and portable sensor for emission monitoring in urban areas.

How to cite: Olivieri, M., Zifarelli, A., Sampaolo, A., Spagnolo, V., and Patimisco, P.: Real time monitoring of N2O and CO emissions from vehicles using a quartz-enhanced photoacoustic sensor, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18041, https://doi.org/10.5194/egusphere-egu25-18041, 2025.

17:10–17:20

EGU25-17864

ECS

On-site presentation

Development of a Laser Heterodyne Radiometer for Atmospheric CO₂ and O₂ Measurements: Comparison with FTIR Data

Adela Collado-Rodríguez, Aldo Moreno-Oyervides, Oscar Elías Bonilla-Manrique, Omaira García, and Pedro Martín-Mateos

There is currently a major global interest in the monitoring of greenhouse gases (GHGs), recognized as the main cause of global warming. At present, the most widely accepted and utilized technique for accurate measurements of GHGs in the atmosphere is Fourier Transform Infrared (FTIR) analysis [1]. These systems are widely used in ground-based monitoring networks, because they provide high accuracy concentration measurements of many trace gases simultaneously. However, the main disadvantage of this type of systems, besides the cost, is its size, which makes it difficult to use for characterizing hot spot GHGs sources. This has led to a growing interest in the development of new, more portable, and compact GHGs systems. In this context, Laser Heterodyne Radiometry (LHR) is seen as a promising alternative to complement and improve current observation systems. The technique characteristics include high optical resolution, flexibility of operation and a compact instrument design. On the other hand, the optical span is restricted by the tuning range of the local oscillator, which generates certain constraints and challenges that still need to be properly studied and addressed.

In LHR systems, the incoming signal is combined with the local oscillator laser and taken to a photodetector, which provides a downshifted radiofrequency (RF) copy of the spectrum of the optical input signal. The RF signal is amplified and filtered to configure the optical resolution of the instrument and detected by a RF power meter [2]. If the laser emission frequency is swept the spectrum of the optical signal can be retrieved.

This contribution will present the development of a novel, high-performance LHR, with optical frequency comb calibration, which allows the measurement of CO₂ and O₂ atmospheric concentrations in the field. The results of a measurement campaign, in which the developed system has been compared in detail with the FTIR spectrometer of the TCCON network at the Izaña Atmospheric Observatory (Spain) [3], will be presented and discussed. We believe that the results obtained provide a clear and promising outlook on the future possibilities of using LHR systems for atmospheric composition monitoring.

[1] D. Wunch et al., “The Total Carbon Column Observing Network’s GGG2014 Data Version,” CaltechDATA, Oct. 2015, doi: 10.14291/TCCON.GGG2014.documentation.R0/1221662.

[2] A. Moreno-Oyervides, O. E. Bonilla-Manrique, O. García, and P. Martín- Mateos, “Design and evaluation of a portable frequency comb-referenced laser heterodyne radiometer,” Opt Lasers Eng, vol. 171, p. 107801, Dec. 2023, doi: 10.1016/J.OPTLASENG.2023.107801.

[3] E. Cuevas et al., “Izaña Atmospheric Research Center Activity Report 2019-2020,” State Meteorological Agency (AEMET), Madrid, Spain and World Meteorological Organization, Geneva, Switzerland, NIPO: 666-22-014-0, WMO/GAW Report No. 276, 2022, https://doi.org/10.31978/666-22-014-0.

How to cite: Collado-Rodríguez, A., Moreno-Oyervides, A., Bonilla-Manrique, O. E., García, O., and Martín-Mateos, P.: Development of a Laser Heterodyne Radiometer for Atmospheric CO₂ and O₂ Measurements: Comparison with FTIR Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17864, https://doi.org/10.5194/egusphere-egu25-17864, 2025.

17:20–17:30

EGU25-6779

ECS

On-site presentation

The ALBATROSS spectrometer for balloon-borne measurements of UTLS water vapor: Laboratory and in-flight validation

Simone Brunamonti, Alex Weitnauer, Philipp Scheidegger, Lukas Emmenegger, and Béla Tuzson

The amount of water vapor (H₂O) in the upper troposphere-lower stratosphere (UTLS) plays a critical role for the Earth's radiative balance. However, due to its low abundance, accurate measurements of H₂O in this region (~8‒25 km altitude) are still very challenging, and large discrepancies were often found between different techniques.

Here, we present the validation of a laser absorption spectrometer, ALBATROSS, specifically developed for balloon-borne measurements of UTLS H₂O [1]. ALBATROSS is a compact (< 3.5 kg) instrument using a continuous-wave (cw) distributed feedback quantum cascade laser (DFB-QCL) emitting at 6.014 μm, and a monolithic segmented circular multipass cell [2] with an optical path length of 6 m within a cell diameter of 10.8 cm. The multipass cell is highly resistant to thermal and mechanical stress, and can be operated both in a closed-path (laboratory) and an open-path (flight) configuration.

The performance of the spectrometer was assessed at UTLS-relevant conditions using SI-traceable reference gases generated by a dynamic-gravimetric permeation method [3]. The results show that ALBATROSS achieves an accuracy better than ±1.5 % with respect to the SI-traceable reference at all investigated pressures (30‒250 mbar) and H₂O amount fractions (2.5‒35 ppm), and a precision better than 0.3 % at 1 s resolution. The quadratic speed dependent Voigt profile (qSDVP) line shape model was implemented to assure this level of accuracy using first principles.

Further laboratory-based validation activities included the AquaVIT4 intercomparison of atmospheric hygrometers, held at the AIDA cloud simulation chamber in Karlsruhe, Germany. Here, the performance of four airborne hygromenters, including ALBATROSS, was evaluated under a wide range of challenging environmental conditions (pressure 20‒600 mbar, temperature 190‒245 K, H₂O amount fraction 0.5‒530 ppm).

Recently, ALBATROSS was deployed in a series of atmospheric test flights conducted from the Meteoswiss Payerne Observatory (Switzerland), within the framework of the Swiss H₂O-Hub project. In tandem with ALBATROSS, a cryogenic frospoint hygrometer (CFH) was also deployed as a reference. Good agreement within ±10 % was found between ALBATROSS and CFH up to about 24 km altitude (~30 mbar pressure).

Altogether, our results demonstrate the exceptional potential of mid-IR laser spectroscopy for in-situ measurements of UTLS H₂O. This is particularly relevant considering the ongoing reconception of the CFH method, currently used in long-term climate monitoring networks (e.g., the GCOS reference upper air network, GRUAN), due to its use of fluoroform (HFC-23) as cooling agent, which must be phased out due to its high global warming potential.

[1] Graf et al., Atmos. Meas. Tech., 14, 1365–1378, 2021.

[2] Graf et al., Opt. Lett., 43, 2434-2437, 2018.

[3] Brunamonti et al., Atmos. Meas. Tech., 16, 4391–4407, 2023.

How to cite: Brunamonti, S., Weitnauer, A., Scheidegger, P., Emmenegger, L., and Tuzson, B.: The ALBATROSS spectrometer for balloon-borne measurements of UTLS water vapor: Laboratory and in-flight validation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6779, https://doi.org/10.5194/egusphere-egu25-6779, 2025.

17:30–17:40

EGU25-9415

ECS

On-site presentation

A dual-comb spectrometer for open-path monitoring of greenhouse gases concentrations above an urban area

Romain Dubroeucq, Tobias D. Schmitt, André Butz, Thomas Pfeifer, and Markus Oberthaler

Remote sensing of trace gases in the atmosphere can be performed with numerous spectrometers relying on different sources of light. Incoherent sources such as those found with typical Fourier transform spectrometers provide broad spectral coverage, thus allowing to measure spectral signatures from multiple species simultaneously. However, this comes at the cost of limited sensitivity and spectral resolution. On the other hand, coherent sources such as lasers offer high spectral brightness and resolution, resulting in high sensitivity and selectivity at the cost of limited spectral coverage. Developed since the advent of the optical frequency comb (OFC) 25 years ago, state-of-the-art spectrometers operating with OFCs as probing light sources combine high sensitivity, high spectral resolution and broad spectral bandwidth. Among all comb-based spectroscopic techniques, dual-comb spectroscopy (DCS) does not require any dispersive or moving optical component to record a spectrum, allowing for relatively small footprints and mechanically robust instruments. This makes dual-comb spectrometers particularly suited for remote sensing [1] and field-deployed operation outside of the optical laboratory [2].

Here, we present the recent technical developments of a near-infrared dual-comb spectrometer for open-path monitoring of greenhouse gases above the city of Heidelberg. The instrument is located at the top of the Institute of Environmental Physics in Heidelberg University campus. The light from two fibered OFCs, spanning 1.58-1.7 µm, is coupled into free space with a telescope, and propagates along a 1.5 km path to a retroreflector array. The reflected signal is picked up by the telescope and coupled back into fiber for detection and data acquisition. We discuss performance of the instrument and the results of our upcoming measurement campaign.

[1] G. B. Rieker et al., "Frequency-comb-based remote sensing of greenhouse gases over kilometer air paths," Optica 1, 290-298 (2014), DOI: 10.1364/OPTICA.1.000290.

[2] S. Coburn et al., "Regional trace-gas source attribution using a field-deployed dual frequency comb spectrometer," Optica 5, 320-327 (2018), DOI: 10.1364/OPTICA.5.000320.

How to cite: Dubroeucq, R., Schmitt, T. D., Butz, A., Pfeifer, T., and Oberthaler, M.: A dual-comb spectrometer for open-path monitoring of greenhouse gases concentrations above an urban area , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9415, https://doi.org/10.5194/egusphere-egu25-9415, 2025.

17:40–17:50

EGU25-14245

ECS

On-site presentation

Single-photon level detection technique of long open-air path dual-comb spectroscopy

Ruocan Zhao and Jiangtao Li

Optical frequency combs are important tools in the field of quantum precision measurement. Over the past decade, dual-comb spectroscopy technology has been widely applied in Earth sciences, especially in atmospheric laser remote sensing. It has demonstrated significant advantages in measurement accuracy and interference resistance compared to traditional laser remote sensing technologies. This work aims to address the key technical bottlenecks in current open-air dual-comb spectroscopy (DCS) technology for long-distance detection and non-cooperative target conditions, focusing on the application of single-photon weak signal detection technology in dual-comb spectroscopy. By introducing photon counting technology, we can achieve high-resolution spectral measurement under extremely low light conditions, significantly enhancing the detection capability of dual-comb spectroscopy. This work will conduct laboratory and field dual-comb spectroscopy experiments, focusing on the reconstruction of dual-comb interference spectra based on photon arrival times, precise spectral modulation and synchronization of optical frequency combs, and spectral processing and inversion algorithms. The research results will provide strong technical support for atmospheric science, environmental monitoring, and fundamental physics research, and are expected to promote the development of global atmospheric multi-element remote sensing technology.

How to cite: Zhao, R. and Li, J.: Single-photon level detection technique of long open-air path dual-comb spectroscopy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14245, https://doi.org/10.5194/egusphere-egu25-14245, 2025.

17:50–18:00

EGU25-19639

ECS

On-site presentation

Development of Open-Path Incoherent BroadBand Cavity Enhanced Absorption Spectroscopy (OP-IBB-CEAS) instruments for the measurement of trace gases in the Irish Atmospheric Simulation Chamber

Mixtli Campos-Pineda, Satheesh Chandran, Amir Ben Brik, Niall O'Sullivan, John Wenger, and Andy Ruth

The study of the reactions of volatile organic compounds (VOCs) in the troposphere is important to assess the impact of biogenic and anthropogenic emissions on climate, health and the economy. The challenge of these studies lies, principally, in the difficulty of designing experiments and instruments to measure VOCs and their reaction products under conditions that are significant for the atmosphere (e.g. low concentrations, short lifetimes). The Irish Atmospheric Simulation Chamber (27 m³ Teflon cuboid) is a research facility for the kinetic and mechanistic study of VOC oxidation processes, and a series of open-path incoherent broadband cavity enhanced absorption spectroscopy (OP-IBB-CEAS) setups have been developed for the measurement of different trace gases that are relevant for the study of atmospheric processes. The open-path characteristic of the IBB-CEAS instruments, ensures that there are no sampling losses and that the concentrations measured correspond directly to those of the trace gases in the static chamber. Currently, four OP-IBB-CEAS setups have been developed for measurements of different trace gases: a) A NIR-IBB-CEAS instrument was developed for the measurement of H₂O and CO₂, b) A visible IBB-CEAS instrument centred at 662 nm for the measurement of H₂O, NO₃, and NO₂, c) A visible IBB-CEAS instrument centred at 450 nm for the measurement of (CHO)₂and NO₂, and d) A UV IBB-CEAS instrument for the measurement of HONO, NO₂ and MACR. The effective mirror reflectivity of the UV-Vis IBB-CEAS instruments was calibrated with NO₂ in a simulated “nighttime” scenario and in a photo-stationary state, using a home-made extractive Cavity Ring-Down Setup. Absorption coefficients for the different instruments range from 10^-9to 10^-8cm^-1. A fast retrieval method based on singular value decomposition (SVD) was integrated into an iterative algorithm for fast and robust determination of the concentrations of the different analytes, corresponding to mixing ratios in the range of pptv (e.g. for NO₃), to ppbv (e.g. for MACR). In this presentation we will report on a series of NO_Yproduction experiments from the reaction of NO₂ and O₃ was conducted to benchmark the response of the IBB-CEAS instruments, and to study NO_Y photolysis. These benchmarking experiments shed some light on the importance of the transition stages between "nighttime" and “daytime” chemistry, and their possible impact on the chemistry of nitrogen oxides.

How to cite: Campos-Pineda, M., Chandran, S., Ben Brik, A., O'Sullivan, N., Wenger, J., and Ruth, A.: Development of Open-Path Incoherent BroadBand Cavity Enhanced Absorption Spectroscopy (OP-IBB-CEAS) instruments for the measurement of trace gases in the Irish Atmospheric Simulation Chamber, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19639, https://doi.org/10.5194/egusphere-egu25-19639, 2025.

Posters on site: Thu, 1 May, 14:00–15:45 | Hall X5

Display time: Thu, 1 May, 14:00–18:00

Chairpersons: Dean Venables, Weidong Chen

X5.131

EGU25-1170

ECS

1.57μm Active Laser Heterodyne Spectrometer and CO2 Concentration Measurement

Xingji Lu, Yinbo Huang, Zhengsong Cao, Haiping Mei, Chaolong Cui, Jun Huang, and Yao Huang

CO₂ is an important greenhouse gas(GHG) that affects the Earth's atmosphere, and continuous measurement of CO₂ helps understand its sources and sinks. The passive laser heterodyne spectrometer(LHS) has been used in meteorology and environmental monitoring recently, especially in the measurement of the radiation properties of the Earth and the densities of atmospheric greenhouse gases. As well known, the passive LHS uses sunlight, the heterodyne efficiency is low, the heterodyne signal processing is complex, and it cannot be measured without sunlight. Therefore, it is difficult for passive LHS to achieve continuous measurement of the GHG of interest. In order to improve the application field of LHS, a 1.57 μm active LHS is investigated and built by using a tunable DFB laser, acoustic-optic frequency shifter and fiber amplifier. It adopts the reflected laser after amplified and frequency shifted as the input light and mixed with seed laser, which possesses the advantage of high coherence efficiency and continuous observation day and night. The CO₂ absorption spectrum measurement in the range of 2.2 km is realized, and the signal-to-noise ratio is about 286. The densities of CO₂ are 419.15 ~ 424.48ppmv during the experiment. The research will make up for the deficiency of the passive laser heterodyne spectrometer.

How to cite: Lu, X., Huang, Y., Cao, Z., Mei, H., Cui, C., Huang, J., and Huang, Y.: 1.57μm Active Laser Heterodyne Spectrometer and CO2 Concentration Measurement, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1170, https://doi.org/10.5194/egusphere-egu25-1170, 2025.

X5.132

EGU25-4475

ECS

Optical sensing platform based on tunable laser absorption spectroscopy for the measurement of carbon dioxide dissolved in seawater

Yongyong Hu, Patrick Augustin, Jingjing Wang, Kun Liu, Ruyue Cui, Hongpeng Wu, Lei Dong, Xiaoming Gao, Marc Fourmentin, Tong Nguyen Ba, and Weidong Chen

Ocean-atmosphere gas exchange plays a critical role in the global carbon cycle, as the ocean acts as both a major sink and source of atmospheric CO₂. This exchange process regulates the Earth's carbon balance and influences climate systems on a global scale. Understanding the mechanisms of CO₂ absorption and release at the ocean surface is essential for accurately assessing the ocean’s contribution to carbon fluxes [1].

The present work introduces the development of a optical sensor based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) for measurement of CO₂ dissolved in seawater. This approach enables real-time measurement of CO₂ concentrations in seawater for evaluation of CO₂ distribution and study of exchange processes between ocean and atmosphere. The developed sensing platform involves a 2008 nm distributed feedback laser coupled to a compact 30-m multipass cell with 7-circle spot dense pattern [2] using wavelength modulation spectroscopy approach [Figure 1]. CO₂ dissolved in seawater is extracted using a custom-designed membrane contactor extraction device.

Figure 1. Experimental measurements of 2f absorption spectra of CO₂ in air and dissolved in seawater.

Performance of the CO₂ sensing platform, experimental details and the preliminary results will be discussed and presented.

Acknowledgments

This work is partially supported by the French national research agency (ANR) under the Labex CaPPA (ANR-10-LABX-005) and the ICAR-HO2 (ANR-20-CE04-0003) contracts, the EU H2020-ATMOS project (Marie Skłodowska-Curie grant agreement No 872081), the regional CPER ECRIN program, and the National Natural Science Foundation of China (Grant No. 62235010). The Région Hauts-de-France and the Pôle Métropolitain de la Côte d’Opale are gratefully acknowledged for PhD scholarship support.

References

[1] Tim DeVries, “The ocean carbon cycle”, Annual Review of Environment and Resources 47 (2022) 317-341.

[2] Kun Liu, Lei Wang, Tu Tan, Guishi Wang, Weijun Zhang, Weidong Chen, Xiaoming Gao, “Highly sensitive detection of methane by near-infrared laser absorption spectroscopy using a compact dense-pattern multipass cell”, Sensors and Actuators B: Chemical 220 (2015) 1000-1005.

How to cite: Hu, Y., Augustin, P., Wang, J., Liu, K., Cui, R., Wu, H., Dong, L., Gao, X., Fourmentin, M., Nguyen Ba, T., and Chen, W.: Optical sensing platform based on tunable laser absorption spectroscopy for the measurement of carbon dioxide dissolved in seawater, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4475, https://doi.org/10.5194/egusphere-egu25-4475, 2025.

X5.133

EGU25-6525

ECS

Subpromille measurements of H2 absorption spectra near 1.2 μm

Hui Liang, Yan Tan, Jing Wang, and Shui Ming Hu

The molecule hydrogen is the most abundant neutral molecule in the universe and dominates the atmosphere of gas giants in the solar system and beyond. Laboratory-measured spectral data of the hydrogen molecule, including transition absorption (?) frequencies, intensities, and related temperature-/pressure-dependent spectroscopic parameters, are the basis for modeling the planetary atmospheres [1].

The present work is based on two high precision cavity enhanced spectroscopy methods. Both absorption and dispersion spectra were recorded with the same frequency-stabilized cavity-enhanced spectroscopy instrument referenced to an optical frequency comb. Doppler-broadened spectra of the first overtone Q(1) line of the H2 molecule near 1.2 µm were measured in the range of 20-80 kPa. The spectrums were fitted by the Hartmann-Tran profile (HTP) [2], which is suitable for molecule hydrogen analysis. The line intensities obtained by the two methods reached an accuracy of 0.15%, and they agree well with theoretical results [3]. It is the first time that subpromille measurements of a rovibrational transition of the hydrogen molecule have been performed with two different methods. The work paves the way for SI-traceable high-precision molecular density measurements based on laser spectroscopy.

The experimental detail and the data analysis results will be presented and discussed.

Acknowledgments

This work was jointly supported by the National Natural Science Foundation of China (Grant Nos. 12393825, 12393822, 22327801, 22241302), the Innovation Program for Quantum Science and Technology (Grant Nos. 2021ZD0303102, 2022YFF0606500), and the Chinese Academy of Sciences (Grant No. YSBR-055).

References

[1] Liu, Q. H., Tan, Y., Cheng, C. F., & Hu, S. M. (2023). Precision spectroscopy of molecular hydrogen. Physical Chemistry Chemical Physics, 25(41), 27914-27925.

[2] Konefał, M., Słowiński, M., Zaborowski, M., Ciuryło, R., Lisak, D., & Wcisło, P. (2020). Analytical-function correction to the Hartmann–Tran profile for more reliable representation of the Dicke-narrowed molecular spectra. Journal of Quantitative Spectroscopy and Radiative Transfer, 242, 106784.

[3] Komasa, J., Puchalski, M., Czachorowski, P., Łach, G., & Pachucki, K. (2019). Rovibrational energy levels of the hydrogen molecule through nonadiabatic perturbation theory. Physical Review A, 100(3), 032519.

How to cite: Liang, H., Tan, Y., Wang, J., and Hu, S. M.: Subpromille measurements of H2 absorption spectra near 1.2 μm, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6525, https://doi.org/10.5194/egusphere-egu25-6525, 2025.

X5.134

EGU25-8094

Sparsity and Non-Negativity Constrained FTIR Spectroscopic Analysis for VOC Detection

Yusheng Qin

Fourier Transform Infrared (FTIR) spectroscopy faces significant challenges in detecting volatile organic compounds (VOCs) within complex environments due to cross-absorption and spectral overlap among components. To address these challenges, an enhanced nonlinear least squares algorithm (SN-NNLS) that integrates sparsity and non-negativity constraints is proposed. The sparse regularization term effectively separates gas components with overlapping absorption features, improving the accuracy of multi-component analysis. Meanwhile, the non-negativity constraint ensures physically meaningful results by eliminating negative concentration estimates, enhancing the reliability of the outcomes. Additionally, the algorithm incorporates dynamic polynomial degree adjustments and nonlinear correction techniques to handle the nonlinear characteristics of diverse spectral datasets, further enhancing its adaptability and robustness. Experimental results demonstrate that the SN-NNLS algorithm significantly improves the precision, stability, and robustness of VOC concentration measurements. This method offers a reliable and efficient solution for quantitative infrared spectral analysis in complex environments.

How to cite: Qin, Y.: Sparsity and Non-Negativity Constrained FTIR Spectroscopic Analysis for VOC Detection, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8094, https://doi.org/10.5194/egusphere-egu25-8094, 2025.

X5.135

EGU25-9240

A net ozone production rate detection system based on dual-channel cavity ring-down spectroscopy

Renzhi Hu, Chuan Lin, Haotian Cai, Guoxian Zhang, Jinzhao Tong, and Pinhua Xie

A newly constructed cavity ring-down spectroscopy (OPR-CRDS) for measuring net photochemical ozone production rates was developed. The system consists of two chambers (a reaction chamber and a reference chamber) and a dual-channel Ox-CRDS detector. The inner surfaces of both chambers are coated with Teflon film to minimize the wall loss of Ox. It was found that even though the photolysis frequency (J value) decreased by 10%, the decrease in the P(O₃) caused by the ultraviolet-blocking film coating was less than 3%. The two chambers had a good consistency in the mean residence time and the measurement of NO₂ and Ox under the condition of no sunlight. The detection limit of the OPR-CRDS was determined to be 0.20 ppbv/hr. To further verify the accuracy of the system, the observed values of the OPR-CRDS were compared with the calculation results based on radical (OH, HO₂, and RO₂) reactions, and a good correlation was obtained. Finally, the developed instrument was applied to the comprehensive field campaign at an urban site in the Yangtze River Delta (China), the time series and change characteristics of the P(O₃) were required directly, and the good environmental adaptability and stability of the OPR-CRDS system were demonstrated. It is expected that the new instrument will be beneficial to investigations of the relationship between P(O₃) and its precursors.

How to cite: Hu, R., Lin, C., Cai, H., Zhang, G., Tong, J., and Xie, P.: A net ozone production rate detection system based on dual-channel cavity ring-down spectroscopy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9240, https://doi.org/10.5194/egusphere-egu25-9240, 2025.

X5.136

EGU25-12911

ECS

Spectroscopy of gas plumes in the laboratory: remote sensing of comets and icy satellites

Dominik Belousov, Omar Mokhtari, Linus Stöckli, Joël Fritschi, Daniele Piazza, Axel Murk, and Nicolas Thomas

Radiometry is a highly accurate technique of gas spectroscopy, widely used in observations of stellar objects (e.g., molecular clouds, accretion discs), planetary atmospheres, comets and icy satellites. Since observations are usually made far from the object, the spectrum detected is a combination of many gas layers lying between the gas source and the observer. Thus, gas models are needed to properly fit observations, which becomes especially challenging in optically thick layers and with large gradients in gas profiles. In addition, optically thick layers can mask the properties of the gas source which have a direct connection with chemical and physical conditions of subsurface layers.

Our project, called WEEVIL (the Water Emission of Vapour from Ice in the Laboratory), concerns the spectroscopy of gas plumes arising from the sublimation of icy, porous and dusty media in controlled laboratory experiments, following [1]. Project objectives are: 1) verification/correction of subsurface models of icy bodies by comparing laboratory and space observations; 2) studying the capabilities of radiometry for determining subsurface material properties.

A heterodyne radiometer operating primarily at the frequency of 557 GHz (water rotational line) is being used to investigate column densities, production rates, temperatures, and outflow gas velocities of sublimed icy samples. An internal cooling system using liquid nitrogen and a cryocooler ensures stable temperature of the sample and radiometer compounds, and mitigates the impact of the vacuum chamber on the gas plume. The radiometer has been developed/procured and is undergoing the necessary sensitivity tests. The vacuum chamber is in the final design/production stage. Measured brightness temperatures by the radiometer will be compared with DSMC (direct simulation Monte Carlo) of gas and radiative transfer calculations. The radiative transfer model includes time dependence due to gas expansion and non-LTE due to non-collisional background, following [2].

[1] O. Auriacombe et al. 2022 MNRAS 515 2

[2] M. A. Cordiner et al 2022 ApJ 929 38

How to cite: Belousov, D., Mokhtari, O., Stöckli, L., Fritschi, J., Piazza, D., Murk, A., and Thomas, N.: Spectroscopy of gas plumes in the laboratory: remote sensing of comets and icy satellites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12911, https://doi.org/10.5194/egusphere-egu25-12911, 2025.

X5.137

EGU25-14308

ECS

Open-path, portable, low-power laser methane sensor system using miniature multi-pass cell for methane mobile monitoring

Gang Wang, Ruyue Cui, Yongyong Hu, Hongpeng Wu, Weidong Chen, and Lei Dong

X5.138

EGU25-15148

ECS

A high-resolution microcavity transmission spectrometer

Bin Yang and Qin Yin

Spectral analysis is one of the most powerful tools for studying and understanding matter. As a key branch, absorption spectroscopy is widely used in material detection, isotope analysis, trace gas detection, and the study of atomic and molecular hyperfine structures. Traditional mode-locked optical frequency combs, which feature broad spectra and low repetition rates, have enabled high-precision absorption measurements through dual-comb techniques. These combs have found applications in trace gas detection, spectral imaging, and isotope analysis. However, their complexity, bulkiness, and large size limit their use outside laboratories. In contrast, low-noise optical frequency combs generated by optical micro-resonators offer significant potential advantages for spectroscopy due to their chip-scale size and lightweight design. We present a microcavity-based transmission spectrometer using a single silicon nitride microcavity soliton, achieving a 4 THz bandwidth with 200 kHz resolution. This system combines the stable dissipative Kerr soliton (DKS) comb from a silicon nitride micro-resonator with the dual-sideband scanning from an intensity electro-optic modulator (EOM), transferring sub-Hz RF precision to the optical domain. The resulting frequency-modulated (FM) comb inherits the high precision of the RF domain, with optical accuracy dominated by the pump laser and repetition rate stability. The DKS comb allows independent locking of the pump laser and repetition rate, facilitating ultra-precise FM comb generation. The frequency-modulated comb is then imaged onto a 2D CCD array using a VIPA in tandem with a diffraction grating, enabling the recording of a composite spectrum during scanning. It is anticipated that using an ultra-narrow linewidth laser locked to an ultra-stable cavity as the pump source could enable Hz-level precision and stability. Given the integration advantages of the key components in this approach, it holds significant potential for future miniaturization, offering vast possibilities for compact, high-precision spectroscopic measurements.

How to cite: Yang, B. and Yin, Q.: A high-resolution microcavity transmission spectrometer, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15148, https://doi.org/10.5194/egusphere-egu25-15148, 2025.

X5.139

EGU25-16084

ECS

A compact mid-IR laser absorption spectrometer for water vapor isotopologue measurements in the upper air

Alex Weitnauer, Lorenz Heilmann, Philipp Scheidegger, Lukas Emmenegger, Dominik Brunner, and Béla Tuzson

Water vapor is the main natural greenhouse gas controlling the Earth's energy balance. It significantly influences atmospheric chemistry and climate dynamics, particularly in the upper troposphere and lower stratosphere (UTLS), which makes it an essential climate variable. Therefore, systematic monitoring of the variability of water vapor in the UTLS is crucial for the understanding of the climate system. However, measurements of its concentration lack important information about the history and origin of the water. This issue can be addressed by considering stable isotopologues of water (e.g. H₂¹⁶O, H₂¹⁸O, and HDO) and quantifying tiny variations in their distribution, which is driven by environmental conditions and chemical/physical processes, making stable water isotopologues an ideal proxy for process studies of the hydrological cycle. Despite the large potential of such measurements, the availability of in-situ data is still very limited due to a lack of adequate analytical tools.

This project focuses on the development of a mobile laser absorption spectrometer (LAS) for airborne in-situ measurements of water vapor isotopologues up to the UTLS region, leveraging on our recent advances in the development of compact instruments [1, 2]. We target the strong absorption features of H₂¹⁶O, H₂¹⁸O, and HDO simultaneously using a single cw-DFB quantum cascade laser (QCL) at around 1359 cm^-1. This range was selected after a detailed spectral survey covering the whole infrared domain. We are currently evaluating a laboratory setup using an astigmatic Herriott multipass cell with an optical path length (OPL) of 76 m to assess the performance of the approach.

The mobile design will rely on our succesful concept [1, 2] including a segmented circular multipass cell [3] in open path configuration, which allows for an effective mitigation of memory effects and exhibits the fastest response time. However, the low abundance of the rare water vapor isotopologues needs to be compensated by substantially extending the OPL (30-fold) to enhance the signal-to-noise ratio. Simulations and laboratory tests have shown that this can be achieved while keeping the rigidity, low weight, and tolerance needed for harsh environmental conditions.

Ultimately, our concept should provide an easy-to-deploy tool for isotope-resolved water vapor profiles at high spatio-temporal resolution.

[1] Graf et al., Atmos. Meas. Tech., 14, 1365–1378, 2021.

[2] Brunamonti et al., Atmos. Meas. Tech., 16, 4391–4407, 2023.

[3] Graf et al., Opt. Lett., 43, 2434-2437, 2018.

How to cite: Weitnauer, A., Heilmann, L., Scheidegger, P., Emmenegger, L., Brunner, D., and Tuzson, B.: A compact mid-IR laser absorption spectrometer for water vapor isotopologue measurements in the upper air, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16084, https://doi.org/10.5194/egusphere-egu25-16084, 2025.

X5.140

EGU25-17500

ECS

A dual-comb spectrometer for remote sensing of greenhouse gases from commercially available devices and components – a progress report.

Tobias D. Schmitt, Romain Dubroeucq, Thomas Pfeifer, André Butz, and Markus K. Oberthaler

Estimating emissions of trace gases into the lower troposphere requires accurate concentration measurements of the species of interest. Most commonly, they are provided by networks of in-situ sensors or remote sensing instruments on satellites. In high-gradient environments (e.g. urban settings), in-situ instruments are only spatially representative for a small area. On the other hand, many satellites average on the kilometer scale on which also the aggregation of the data for inversion modelling takes place. But satellites can only provide data for sunny weather conditions, at best once a day in a specific region and typically lack sensitivity for local enhancements. Path averaged measurements of trace gases can potentially fill this observation gap. Between all the technological options for such measurements, dual comb spectroscopy (DCS) can provide high resolution spectra at high brightness with basically no instrument line function, all of which have already been demonstrated in the field [1]. But the high costs and the amount of experience required to set up and run such a system limit the application to metrology experts. With developments in recent years, like the commercial availability of turn-key frequency combs, DCS becomes a more realistic option for a wider scientific community and industry.

Here, we present our DCS setup, which is intended for greenhouse gas quantification in the near infra-red. Where possible, we used readily available parts and solutions. We present our current setup and first results obtained, as well as lessons learned and experiences gained in the process.

[1] Sean Coburn et al., "Regional trace-gas source attribution using a field-deployed dual frequency comb spectrometer," Optica 5, 320-327 (2018), DOI: 10.1364/OPTICA.5.000320.

How to cite: Schmitt, T. D., Dubroeucq, R., Pfeifer, T., Butz, A., and Oberthaler, M. K.: A dual-comb spectrometer for remote sensing of greenhouse gases from commercially available devices and components – a progress report., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17500, https://doi.org/10.5194/egusphere-egu25-17500, 2025.

X5.141

EGU25-18251

ECS

Heterodyne Spectroradiometer for Precise Measurements of Carbon Dioxide

Iskander Gazizov and Bernhard Lendl

Recent developments around instrumental control of carbon balance are aimed at accurate evaluation of sources and sinks of major greenhouse gases (GHG) by natural landscapes, cities, industrial and agricultural objects. And we see a significant progress in the development of instruments based on commercial telecom components to make global GHG measurements accessible [1].

Fig. 1. Prototype of MLHS instrument performing measurements in Arctic region.

Here we present the Multichannel Laser Heterodyne Spectroradiometer (MLHS) for exploring the Earth's atmosphere in the near-infrared range, addressing the lack of coverage for greenhouse gases in existing measurement networks. High spectral resolution of solar occultation heterodyne spectroscopy enables us to study the structure and dynamics of the atmosphere while maintaining a compact and low-cost design.

Following the 2022 measurement campaign with a Fourier-spectrometer station for CO₂ and CH₄, we identified key limitations of the prototype. By improving thermal stability, optimizing optical scheme, and applying accurate sensors for atmospheric parameters, we are presenting the next generation of MLHS.

References

[1] Zenevich, Sergei, et al. "A concept of 2U spaceborne multichannel heterodyne spectroradiometer for greenhouse gases remote sensing." Remote Sensing 13.12 (2021): 2235.

How to cite: Gazizov, I. and Lendl, B.: Heterodyne Spectroradiometer for Precise Measurements of Carbon Dioxide, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18251, https://doi.org/10.5194/egusphere-egu25-18251, 2025.

X5.142

EGU25-20358

Design of a Laser Heterodyne Radiometer (LHR) Sensor for Wildfire Detection and Characterization

J. Houston Miller and Erin McCaughey

Fire detection has traditionally been done optically using tools, ranging from human eyes to modern, advanced hyperspectral cameras. Both the intensity as well as the spectral signature of the light emitting from fires are important parameters to quantify and characterize. Our laboratory is developing and constructing two sensor platforms to demonstrate a novel technology in Fire Optical Measurements (FOM) for both laboratory and simple “field-scale” demonstrations. The first system, to be described in this presentation, operates in the near-infrared region and will focus on potassium light emissions (K-FOM). Radiative emissions from hot potassium are characteristic of intense fires involving biological materials, distinguishing them from fossil fuel combustion.

The system design for K-FOM is framed by our prior experience in developing Laser Heterodyne Radiometry (LHR) sensors used in solar occultation measurements of greenhouse gases, employing a similar optical design. In K-FOM, light from a flame containing potassium is collected onto a single-mode optical fiber. The collected radiation is mixed with light from a tunable diode laser (Eblana Photonics), operating near 770 nm, using a 2x2 combiner. The two output fibers from the combiner arerouted to a a balanced detector (Thorlabs), and the resulting radio frequency (rf) power is measured using a Digikey power sensor.

In this presentation, the design and characterization of the K-FOM sensor will be described, along with tests using laboratory flame burners. Simple field demonstrations are planned for calendar year 2025.

How to cite: Miller, J. H. and McCaughey, E.: Design of a Laser Heterodyne Radiometer (LHR) Sensor for Wildfire Detection and Characterization, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20358, https://doi.org/10.5194/egusphere-egu25-20358, 2025.

X5.143

EGU25-2361

High-performance data acquisition and processing system based on SOM-FPGA and its application in optical instruments

Weixiong Zhao, Shichuan Ni, Jiacheng Zhou, Weijun Zhang, and Weidong Chen

An ideal data acquisition and processing system has the characteristics of high integration, low latency, wide applicability, and scalability. Its development plays a vital role in the advancement of optical instruments. Most of the data acquisition and processing systems currently used are based on digital signal processing (DSP) or system-on-chip (SoC) architectures, which are limited in processor performance, number of interfaces, and edge computing capabilities. In this presentation, we report a data acquisition system (SOM-FPGA lock-in, SFLI) based on modular system-on-module (SOM) and field-programmable gate array (FPGA) architecture. The SFLI system integrates high-speed signal acquisition and processing, digital lock-in amplifier (DLIA), and edge data storage functions, improves the edge computing capability of the system, and has the advantages of high performance, multiple interfaces, and low cost. The system can simultaneously achieve four-channel high-speed acquisition (sampling rate up to 65 MSPS) and digital phase sensitive detector (demodulation frequency from DC to 5 MHz). When the modulation frequency is 20 kHz and the input voltage range is 1 V, the input voltage noise of the SFLI system is about 41 nV/√Hz. The performance of the SFLI system is compared with that of a commercial lock-in amplifier, showing good consistency. The SFLI has been applied to cavity-enhanced spectroscopy technology, providing a new solution for the miniaturization of optical instruments and edge computing in practical applications.

How to cite: Zhao, W., Ni, S., Zhou, J., Zhang, W., and Chen, W.: High-performance data acquisition and processing system based on SOM-FPGA and its application in optical instruments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2361, https://doi.org/10.5194/egusphere-egu25-2361, 2025.

X5.144

EGU25-19036

Potential capabilities of CO2 measurement in the atmospheric column using a near infrared laser heterodyne radiometer (LHR)

Weidong Chen, Marie Thérèse El Kattar, Tingting Wei, Aditya Saxena, and Hervé Herbin

Vertical concentration distributions of atmospheric trace gases, depending on vertical air transport from the Earth’s surface to the tropopause, play crucial roles in air pollution, ozone depletion and climate change. Accurate determination of the mixing ratios of the greenhouse gases (GHGs) in the lower troposphere, is thus important in the current international context of fighting against global warming and climate change. Laser heterodyne radiometry (LHR) technique, which extracts target molecular absorption information from the broadband sunlight by beating it with a local oscillator for heterodyne measurement, is a highly effective method for ground-based remoting measurement of GHGs’ concentration and vertical profile in the atmospheric column [1].

A transportable, all-fiber-coupled LHR instrument has been developed at the LPCA for ground-based remote sensing of carbon dioxide (CO₂) [2] in the atmospheric column by using a wide band tunable external-cavity diode laser (1520 – 1620 nm) as local oscillator. The measured LHR spectra of CO₂ in the atmospheric column demonstrate strong agreement with spectra recorded by FTIR spectrometer of the TCCON at Paris and simulated from atmospheric transmission model.

The main objective of this study is to quantify the contribution of the LHR to the measurement of tropospheric abundances of CO₂ in the atmospheric column from the ground. We present the LHR’s capabilities to measure CO₂ vertical profiles through a complete information content analysis, a channel selection and an error budget estimation, using the radiative transfer model ARAHMIS (Atmospheric Radiation Algorithm for High-Spectral Resolution Measurements from Infrared Spectrometers), developed at the LOA [3]. A comparison with the other ground-based instruments like the EM27/SUN and the IFS125HR of the TCCON networks are also presented.

Acknowledgments

This work is partially supported by the French national research agency (ANR) under the Labex CaPPA (ANR-10-LABX-005) contract, the EU H2020-ATMOS project (Marie Skłodowska-Curie grant agreement No 872081), the regional CPER ECRIN program, and the CNES ATMOSFER project.

References

[1] D. Weidmann, "Atmospheric trace gas measurements using laser heterodyne spectroscopy", Ch. 4, pp. 159-223, in Advances in Spectroscopic Monitoring of the Atmosphere, eds. by Weidong Chen, Dean S. Venables, Markus W. Sigrist, ISBN: 978-0-12-815014-6, Elsevier (2021).

[2] J. Wang, T. Tu, F. Zhang, F. Shen,J. Xu, Z. Cao, X. Gao, S. Plus, and W. Chen, "An external-cavity diode laser-based near-infrared broadband laser heterodyne radiometer for remote sensing of atmospheric CO₂", Optics Express 31 (2023) 9251-9263.

[3] M.T. El Kattar, F. Auriol, H. Herbin, “Instrumental Characteristics and potential greenhouse gas measurement capabilities of the Compact High-Spectral-Resolution Infrared spectrometer: CHRIS”, Atmospheric Measurement Technique 13 (2020) 3769-3786.

How to cite: Chen, W., El Kattar, M. T., Wei, T., Saxena, A., and Herbin, H.: Potential capabilities of CO2 measurement in the atmospheric column using a near infrared laser heterodyne radiometer (LHR), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19036, https://doi.org/10.5194/egusphere-egu25-19036, 2025.

X5.146

EGU25-7781

Measurement of Pollutants in Petrochemical Complexes Using Spectroscopic Remote Sensing Techniques

(withdrawn)

Jeonghun Kim, Sunghwan Cho, Wonseok Jung, and Daeil Kang

X5.147

EGU25-13275

ECS

New experimental measurements of the Collision-Induced Absorptions of H2-H2 and H2-He in the 3600-5500 cm-1 spectral range from 120 to 500 K

Francesca Vitali, Stefania Stefani, Giuseppe Piccioni, Marcel Snels, Davide Grassi, David Biondi, and Angelo Boccaccini

The atmospheres of the gaseous and icy giant planets represent a high-density environment, whose composition is generally dominated by H₂ and He.

Consequently, the H₂ Collision-Induced Absorption (CIA) represents one of the main sources of opacity in the near-infrared spectral range between 1 and 5 μm, a spectral range widely used by remote sensing instruments.

To reduce the retrieval uncertainty of the atmospheric gases, it is very important to have experimental data on the CIA absorption compared with the available theoretical models. These models are necessary in any case where these are missing due to technological limits in the lab.

We measured in our lab the H₂ CIA fundamental band in the [3600, 5500] cm^-1 spectral range using an experimental setup called PASSxS (Planetary Atmosphere Simulation for Spectroscopy) (Snels et al, 2021).

This setup consists of a simulation chamber that contains a Multi-Pass cell coupled with a Fourier spectrometer and aligned to reach an optical path of 3.28 m. The chamber can be heated up to 550 K, cooled down to 100 K, and sustain pressures up to 70 bar.

We measured the H₂-H₂ and H₂-He binary absorption coefficients for temperatures going from 120 to 550 K by using a pure H₂ gas and an H₂-He mixture, as shown in Figures 1 and 2.

Figure 1: H₂-H₂ binary absorption coefficients

Figure 2: H₂-He binary absorption coefficients

A large water vapor absorption can be noted on the band’s wings, highlighted by the two light blue rectangles.

The results obtained have been recently published (Vitali et al., 2024) and the data can be downloaded from the Zenodo platform at the following link https://doi.org/10.5281/zenodo.13142014.

Those measurements can be of particular interest in the field of planetary atmospheres since they can be recombined to obtain the total absorption coefficients, at a fixed temperature, of a H₂-He mixture for any desired mixing ratio.

Moreover, these are essential input parameters when using radiative transfer models such as the NASA Planetary Spectrum Generator (PSG).

We plan to extend the investigation of the CIA in a wider spectral range, including the [7500, 9500] cm^-1 range interested by the H₂CIA first overtone band, with a more detailed temperature scale for both spectral ranges.

Figures 1 and 2 show the so-called interference dips (Van Kranendonk, 1968) around 4150 cm^-1 and 4700 cm^-1, which represent a lack of absorption at specific wavelengths not taken into account by the CIA models.

A further investigation of the density dependence of those features is already in progress, by exploiting the new Fourier spectrometer at a higher spectral resolution and the entire optical path in vacuum.

We plan to perform high-resolution measurements at different densities using both a pure H2 gas and a H2-He mixture. We will use the line profile developed by Van Kranendonk to study the dependence of the inter-collisional halfwidth on density. Finally, we will also investigate the dip’s behavior while varying the He mixing ratio.

Acknowledgments: This work has been developed under the ASI-INAF agreement n. 2023-6-HH.0.

How to cite: Vitali, F., Stefani, S., Piccioni, G., Snels, M., Grassi, D., Biondi, D., and Boccaccini, A.: New experimental measurements of the Collision-Induced Absorptions of H2-H2 and H2-He in the 3600-5500 cm-1 spectral range from 120 to 500 K , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13275, https://doi.org/10.5194/egusphere-egu25-13275, 2025.

X5.150

EGU25-15692

ECS

Design of a new cryogenically cooled radiometer for middle atmospheric water vapor measurements:CRYOWARA

Adrianos Filinis, Gunter Stober, and Axel Murk

Continuous monitoring of atmospheric trace gases in the middle atmosphere presents
significant challenges. Remote sensing instruments are essential for understanding and
characterizing changes in atmospheric chemical composition. Although water vapor is
present in low concentrations in the middle atmosphere, it plays a critical role as one
of the most significant greenhouse gases, profoundly influencing climate change. Water
vapor is a key climate variable, important for radiative balance, and is involved in various
chemical reactions, including ozone depletion through the formation of polar stratospheric
clouds.
With the decommissioning of the AURA-MLS 183 GHz water vapor line, there is an
increasing need to expand the ground-based network of microwave (MW) radiometers.
At the Institute of Applied Physics (IAP), within the Microwave Group (MW), we have
designed a new cryogenically cooled radiometer to measure the emitted radiation from the
22 GHz water vapor line. This instrument, called CRYOWARA, is intended to replace
the existing 22 GHz radiometer known as MIAWARA, which is currently used by the
MW group at the Zimmerwald observatory in Switzerland.
The primary distinction of CRYOWARA is its partially cryogenically cooled front end,
which significantly reduces instrumental noise. This enhancement will enable more ac-
curate water vapor retrievals at higher altitudes, further advancing the study of middle
atmospheric dynamics. At the EGU 2025 conference, we will present the instrument’s
design along with some preliminary results from the breadboard assembly.

How to cite: Filinis, A., Stober, G., and Murk, A.: Design of a new cryogenically cooled radiometer for middle atmospheric water vapor measurements:CRYOWARA, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15692, https://doi.org/10.5194/egusphere-egu25-15692, 2025.