scholarly journals Airborne Mid-Infrared Cavity enhanced Absorption spectrometer (AMICA)

2021 ◽  
Vol 14 (8) ◽  
pp. 5271-5297
Author(s):  
Corinna Kloss ◽  
Vicheith Tan ◽  
J. Brian Leen ◽  
Garrett L. Madsen ◽  
Aaron Gardner ◽  
...  
Keyword(s):  
Time Resolution ◽  
Atmospheric Measurements ◽  
Mid Infrared ◽  
Infrared Wavelength ◽  
Mixing Ratios ◽  
Enhanced Absorption ◽  
Wide Range ◽  
Research Aircraft ◽  
Saturation Effects ◽  
Absorption Spectrometer

Abstract. We describe the Airborne Mid-Infrared Cavity enhanced Absorption spectrometer (AMICA) designed to measure trace gases in situ on research aircraft using Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS). AMICA contains two largely independent and exchangeable OA-ICOS arrangements, allowing for the simultaneous measurement of multiple substances in different infrared wavelength windows tailored to scientific questions related to a particular flight mission. Three OA-ICOS setups have been implemented with the aim to measure OCS, CO2, CO, and H2O at 2050 cm−1; O3, NH3, and CO2 at 1034 cm−1; and HCN, C2H2, and N2O at 3331 cm−1. The 2050 cm−1 setup has been characterized in the laboratory and successfully used for atmospheric measurements during two campaigns with the research aircraft M55 Geophysica and one with the German HALO (High Altitude and Long Range Research Aircraft). For OCS and CO, data for scientific use have been produced with 5 % accuracy (15 % for CO below 60 ppb, due to additional uncertainties introduced by dilution of the standard) at typical atmospheric mixing ratios and laboratory-measured 1σ precision of 30 ppt for OCS and 3 ppb for CO at 0.5 Hz time resolution. For CO2, high absorption at atmospheric mixing ratios leads to saturation effects that limit sensitivity and complicate the spectral analysis, resulting in too large uncertainties for scientific use. For H2O, absorption is too weak to be measured at mixing ratios below 100 ppm. By further reducing electrical noise and improving the treatment of the baseline in the spectral retrieval, we hope to improve precision for OCS and CO, resolve the issues inhibiting useful CO2 measurements, and lower the detection limit for H2O. The 1035 and 3331 cm−1 arrangements have only partially been characterized and are still in development. Although both setups have been flown and recorded infrared spectra during field campaigns, no data for scientific use have yet been produced due to unresolved deviations of the retrieved mixing ratios to known standards (O3) or insufficient sensitivity (NH3, HCN, C2H2, N2O). The ∼100 kg instrument with a typical in-flight power consumption of about 500 VA is dimensioned to fit into one 19 in. rack typically used for deployment inside the aircraft cabin. Its rugged design and a pressurized and temperature-stabilized compartment containing the sensitive optical and electronic hardware also allow for deployment in payload bays outside the pressurized cabin even at high altitudes of 20 km. A sample flow system with two parallel proportional solenoid valves of different size orifices allows for precise regulation of cavity pressure over the wide range of inlet port pressures encountered between the ground and maximum flight altitudes. Sample flow of the order of 1 SLM (standard litre per minute) maintained by an exhaust-side pump limits the useful time resolution to about 2.5 s (corresponding to the average cavity flush time), equivalent to 500 m distance at a typical aircraft speed of 200 m s−1.

scholarly journals Airborne Mid-Infrared Cavity enhanced Absorption spectrometer (AMICA)

2021 ◽  
Author(s):  
Corinna Kloss ◽  
Vicheith Tan ◽  
J. Brian Leen ◽  
Garrett L. Madsen ◽  
Aaron Gardner ◽  
...  
Keyword(s):  
Atmospheric Measurements ◽  
Mid Infrared ◽  
Infrared Wavelength ◽  
Enhanced Absorption ◽  
Cavity Output ◽  
Wide Range ◽  
Research Aircraft ◽  
Electronic Hardware ◽  
Scientific Questions ◽  
Absorption Spectrometer

Abstract. We describe the Airborne Mid-Infrared Cavity enhanced Absorption spectrometer (AMICA) designed to measure trace gases in situ on research aircraft using Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS). AMICA contains two largely independent and exchangeable OA-ICOS arrangements, allowing for the simultaneous measurement of multiple substances in different infrared wavelength windows tailored to scientific questions related to a particular flight mission. Three OA-ICOS setups have been implemented to measure OCS, CO2, CO and H2O at 2050 cm−1, O3, NH3 and CO2 at 1035 cm−1, and HCN, C2H2 and N2O at 3331 cm−1. The 2050 cm−1 setup has been fully characterized in the lab and successfully used for atmospheric measurements during two campaigns with the research aircraft M55-Geophysica and one with the German HALO aircraft. Nominal measurement precision is 30 ppt for OCS, 1 ppm for CO2, 3 ppb for CO and 100 ppm for H2O. The 1035 and 3331 cm−1 arrangements have only partially been characterized and are still in development. The ~100 kg instrument with a typical in-flight power consumption of about 500 VA is dimensioned to fit into one 19 inch rack typically used for deployment inside the aircraft cabin. Its rugged design and a pressurized and temperature stabilized compartment containing the sensitive optical and electronic hardware also allow for deployment in payload bays outside the pressurized cabin even at high altitudes of 20 km. A sample flow system with two parallel proportional solenoid valves of different size orifices allows for precise regulation of cavity pressure over the wide range of inlet port pressures encountered between the ground and maximum flight altitudes. Sample flow on the order of 1 SLM maintained by an exhaust-side pump limits the useful time resolution to about 2.5 s (corresponding to the average cavity flush time).

scholarly journals The development and evaluation of airborne in situ N<sub>2</sub>O and CH<sub>4</sub> sampling using a Quantum Cascade Laser Absorption Spectrometer (QCLAS)

2015 ◽  
Vol 8 (8) ◽  
pp. 8859-8902 ◽  
Author(s):  
J. R. Pitt ◽  
M. Le Breton ◽  
G. Allen ◽  
C. J. Percival ◽  
M. W. Gallagher ◽  
...  
Keyword(s):  
Quantum Cascade Laser ◽  
Ambient Pressure ◽  
Calibration Procedure ◽  
Atmospheric Measurements ◽  
Quantum Cascade ◽  
Laser Absorption ◽  
Influence Of Water ◽  
Research Aircraft ◽  
Potential Case ◽  
Absorption Spectrometer

Abstract. Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large Atmospheric Research Aircraft. We present details of the mid-IR Aerodyne Research Inc. Quantum Cascade Laser Absorption Spectrometer (QCLAS) employed, including its configuration for airborne sampling, and evaluate its performance over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. A new in-flight calibration procedure to account for the observed sensitivity of the instrument to ambient pressure changes is described, and its impact on instrument performance is assessed. Test flight data linking this sensitivity to changes in cabin pressure is presented. Total 1σ uncertainties of 1.81 ppb for CH4 and 0.35 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ = 5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Los Gatos Research Fast Greenhouse Gas Analyser (FGGA). Finally, a potential case study for the estimation of a regional N2O flux using a mass balance technique is identified, and the method for calculating such an estimate is outlined.

scholarly journals Ozone budget in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis) campaign

2009 ◽  
Vol 9 (2) ◽  
pp. 6979-7032
Author(s):  
M. Saunois ◽  
C. E. Reeves ◽  
C. Mari ◽  
J. G. Murphy ◽  
D. J. Stewart ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Lower Troposphere ◽  
Atmospheric Measurements ◽  
Air Masses ◽  
African Monsoon ◽  
Mixing Ratios ◽  
Budget Analysis ◽  
Multidisciplinary Analysis ◽  
Ozone Maximum ◽  
Research Aircraft

Abstract. A bi-dimensional latitudinal-vertical meterological model coupled with O3-NOx-VOC chemistry is used to reproduce the distribution of ozone and precursors in the boundary layer over West Africa during the African Monsoon Multidisciplinary Analysis (AMMA) campaign as observed on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft. The model reproduces the increase of ozone mixing ratios in the boundary layer observed between the forested region south of 13° N and the Sahelian area northward. Sensitivity and budget analysis reveals that the intertropical convergence zone is a moderate source of O3 rich-air in the boundary layer due to convective downdrafts. Dry deposition drives the ozone minimum over the vegetated area. The combination of high NOx emissions from soil north of 13° N and northward advection by the monsoon flux of VOC-enriched air masses contributes to the ozone maximum simulated at higher latitudes. Simulated OH exhibit a well marked latitudinal gradient with minimum concentrations over the vegetated region where the reactions with biogenic compounds predominate. The model underestimates the observed OH mixing ratios, however this model discrepancy has slight effect on ozone budget and does not alter the conclusions.

scholarly journals Measurement of glyoxal using an incoherent broadband cavity enhanced absorption spectrometer

2008 ◽  
Vol 8 (4) ◽  
pp. 16517-16553 ◽  
Author(s):  
R. A. Washenfelder ◽  
A. O. Langford ◽  
H. Fuchs ◽  
S. S. Brown
Keyword(s):  
Rayleigh Scattering ◽  
Optical Cavity ◽  
Field Measurements ◽  
Array Detector ◽  
Enhanced Absorption ◽  
Minimum Detectable Absorption ◽  
Wide Range ◽  
Path Lengths ◽  
A Charge ◽  
Absorption Spectrometer

Abstract. We describe an instrument for simultaneous measurements of glyoxal (CHOCHO) and nitrogen dioxide (NO2) using cavity enhanced absorption spectroscopy with a broadband light source. The output of a Xenon arc lamp is coupled into a 1 m optical cavity, and the spectrum of light exiting the cavity is recorded by a grating spectrometer with a charge-coupled device (CCD) array detector. The mirror reflectivity and effective path lengths are determined from the known Rayleigh scattering of He and dry zero air (N2+O2). Least-squares fitting, using published reference spectra, allow the simultaneous retrieval of CHOCHO, NO2, O4, and H2O in the 441 to 469 nm spectral range. For a 1-min sampling time, the minimum detectable absorption is 4×10−10 cm−1, and the precision (±1σ) on signal for measurements of CHOCHO and NO2 is 29 pptv and 20 pptv, respectively. We directly compare the incoherent broadband cavity enhanced absorption spectrometer to 404 and 532 nm cavity ringdown instruments for CHOCHO and NO2 detection, and find linear agreement over a wide range of concentrations. The instrument has been tested in the laboratory with both synthetic and real air samples, and the demonstrated sensitivity and specificity suggest a strong potential for field measurements of both CHOCHO and NO2.

scholarly journals Development of a cavity-enhanced absorption spectrometer for airborne measurements of CH<sub>4</sub> and CO<sub>2</sub>

2013 ◽  
Vol 6 (5) ◽  
pp. 1095-1109 ◽  
Author(s):  
S. J. O'Shea ◽  
S. J.-B. Bauguitte ◽  
M. W. Gallagher ◽  
D. Lowry ◽  
C. J. Percival
Keyword(s):  
Biomass Burning ◽  
Dry Matter ◽  
First Year ◽  
Atmospheric Measurements ◽  
Airborne Measurements ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Research Aircraft ◽  
Infrared Spectrometer ◽  
Term Performance

Abstract. High-resolution CH4 and CO2 measurements were made on board the FAAM BAe-146 UK (Facility for Airborne Atmospheric Measurements, British Aerospace-146) atmospheric research aircraft during a number of field campaigns. The system was based on an infrared spectrometer using the cavity-enhanced absorption spectroscopy technique. Correction functions to convert the mole fractions retrieved from the spectroscopy to dry-air mole fractions were derived using laboratory experiments and over a 3 month period showed good stability. Long-term performance of the system was monitored using WMO (World Meteorological Office) traceable calibration gases. During the first year of operation (29 flights) analysis of the system's in-flight calibrations suggest that its measurements are accurate to 1.28 ppb (1σ repeatability at 1 Hz = 2.48 ppb) for CH4 and 0.17 ppm (1σ repeatability at 1 Hz = 0.66 ppm) for CO2. The system was found to be robust, no major motion or altitude dependency could be detected in the measurements. An inter-comparison between whole-air samples that were analysed post-flight for CH4 and CO2 by cavity ring-down spectroscopy showed a mean difference between the two techniques of −2.4 ppb (1σ = 2.3 ppb) for CH4 and −0.22 ppm (1σ = 0.45 ppm) for CO2. In September 2012, the system was used to sample biomass-burning plumes in Brazil as part of the SAMBBA project (South AMerican Biomass Burning Analysis). From these and simultaneous CO measurements, emission factors for savannah fires were calculated. These were found to be 2.2 ± 0.2 g (kg dry matter)−1 for CH4 and 1710 ± 171 g (kg dry matter)−1 for CO2, which are in excellent agreement with previous estimates in the literature.

scholarly journals Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR

2017 ◽  
Vol 10 (10) ◽  
pp. 4023-4053 ◽  
Author(s):  
Hendrik Fuchs ◽  
Anna Novelli ◽  
Michael Rolletter ◽  
Andreas Hofzumahaus ◽  
Eva Y. Pfannerstill ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
Water Vapour ◽  
Organic Compounds ◽  
Time Resolution ◽  
Limit Of Detection ◽  
Measurement Techniques ◽  
Atmospheric Measurements ◽  
Wide Range ◽  
Chemical Conditions ◽  
Simulation Chamber

Abstract. Hydroxyl (OH) radical reactivity (kOH) has been measured for 18 years with different measurement techniques. In order to compare the performances of instruments deployed in the field, two campaigns were conducted performing experiments in the atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich in October 2015 and April 2016. Chemical conditions were chosen either to be representative of the atmosphere or to test potential limitations of instruments. All types of instruments that are currently used for atmospheric measurements were used in one of the two campaigns. The results of these campaigns demonstrate that OH reactivity can be accurately measured for a wide range of atmospherically relevant chemical conditions (e.g. water vapour, nitrogen oxides, various organic compounds) by all instruments. The precision of the measurements (limit of detection  < 1 s−1 at a time resolution of 30 s to a few minutes) is higher for instruments directly detecting hydroxyl radicals, whereas the indirect comparative reactivity method (CRM) has a higher limit of detection of 2 s−1 at a time resolution of 10 to 15 min. The performances of the instruments were systematically tested by stepwise increasing, for example, the concentrations of carbon monoxide (CO), water vapour or nitric oxide (NO). In further experiments, mixtures of organic reactants were injected into the chamber to simulate urban and forested environments. Overall, the results show that the instruments are capable of measuring OH reactivity in the presence of CO, alkanes, alkenes and aromatic compounds. The transmission efficiency in Teflon inlet lines could have introduced systematic errors in measurements for low-volatile organic compounds in some instruments. CRM instruments exhibited a larger scatter in the data compared to the other instruments. The largest differences to reference measurements or to calculated reactivity were observed by CRM instruments in the presence of terpenes and oxygenated organic compounds (mixing ratio of OH reactants were up to 10 ppbv). In some of these experiments, only a small fraction of the reactivity is detected. The accuracy of CRM measurements is most likely limited by the corrections that need to be applied to account for known effects of, for example, deviations from pseudo first-order conditions, nitrogen oxides or water vapour on the measurement. Methods used to derive these corrections vary among the different CRM instruments. Measurements taken with a flow-tube instrument combined with the direct detection of OH by chemical ionisation mass spectrometry (CIMS) show limitations in cases of high reactivity and high NO concentrations but were accurate for low reactivity (< 15 s−1) and low NO (< 5 ppbv) conditions.

scholarly journals An aircraft based three channel broadband cavity enhanced absorption spectrometer for simultaneous measurements of NO<sub>3</sub>, N<sub>2</sub>O<sub>5</sub> and NO<sub>2</sub>

2011 ◽  
Vol 4 (3) ◽  
pp. 3499-3544 ◽  
Author(s):  
O. J. Kennedy ◽  
B. Ouyang ◽  
J. M. Langridge ◽  
M. J. S. Daniels ◽  
S. Bauguitte ◽  
...  
Keyword(s):  
Thermal Dissociation ◽  
Atmospheric Measurements ◽  
Night Time ◽  
Optical Cavities ◽  
Airborne Measurements ◽  
Enhanced Absorption ◽  
The North ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Research Aircraft ◽  
Oxidation Chemistry

Abstract. A three channel broadband cavity enhanced absorption spectroscopy (BBCEAS) instrument has been developed for airborne measurements of atmospheric trace gases involved in night-time oxidation chemistry and air quality. The instrument was deployed on board the Facility for Airborne Atmospheric Measurements BAe 146-301 atmospheric research aircraft during the Role of Nighttime Chemistry in Controlling the Oxidising Capacity of the Atmosphere (RONOCO) measurement campaigns between December 2009 and January 2011. In its present configuration (i.e. specifications of the cavity optics and spectrometers) the instrument is designed to measure NO3, N2O5 (by detection of NO3 after thermal dissociation of N2O5), H2O and NO2 by characterising the wavelength dependent optical attenuation within ambient samples by molecular absorption around 662 nm (NO3 and H2O) and 445 nm (NO2). This paper reports novel advancements in BBCEAS instrumentation including a refined method for performing BBCEAS mirror reflectivity calibrations using measurements of the phase delay introduced by the optical cavities to amplitude modulated radiation. Furthermore, a new methodology is introduced for fitting the strong but unresolved transitions of water vapour, which is required for accurate retrieval of water absorption features from the 662 nm absorption band used to measure NO3 concentrations. The paper also details the first example of airborne measurements of NO3, N2O5 and NO2 over Europe from a flight over the North Sea and Thames Estuary on the night of the 20 July 2010, one of the most polluted days of the RONOCO summertime flying period. As part of this analysis, the performance of the BBCEAS instrument is assessed by comparing airborne NO2 measurements to those reported concurrently by a photolytic chemiluminescence based detector.

Demonstration of a Mid-Infrared Cavity Enhanced Absorption Spectrometer for Breath Acetone Detection

2012 ◽  
Vol 85 (2) ◽  
pp. 846-850 ◽  
Author(s):  
Luca Ciaffoni ◽  
Gus Hancock ◽  
Jeremy J. Harrison ◽  
Jean-Pierre H. van Helden ◽  
Cathryn E. Langley ◽  
...  
Keyword(s):  
Mid Infrared ◽  
Enhanced Absorption ◽  
Breath Acetone ◽  
Acetone Detection ◽  
Absorption Spectrometer

scholarly journals An aircraft based three channel broadband cavity enhanced absorption spectrometer for simultaneous measurements of NO<sub>3</sub>, N<sub>2</sub>O<sub>5</sub> and NO<sub>2</sub>

2011 ◽  
Vol 4 (9) ◽  
pp. 1759-1776 ◽  
Author(s):  
O. J. Kennedy ◽  
B. Ouyang ◽  
J. M. Langridge ◽  
M. J. S. Daniels ◽  
S. Bauguitte ◽  
...  
Keyword(s):  
Thermal Dissociation ◽  
Atmospheric Measurements ◽  
Night Time ◽  
Optical Cavities ◽  
Airborne Measurements ◽  
Enhanced Absorption ◽  
The North ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Research Aircraft ◽  
Oxidation Chemistry

Abstract. A three channel broadband cavity enhanced absorption spectroscopy (BBCEAS) instrument has been developed for airborne measurements of atmospheric trace gases involved in night-time oxidation chemistry and air quality. The instrument was deployed on board the Facility for Airborne Atmospheric Measurements BAe 146-301 atmospheric research aircraft during the Role of Nighttime Chemistry in Controlling the Oxidising Capacity of the Atmosphere (RONOCO) measurement campaigns between December 2009 and January 2011. In its present configuration (i.e. specifications of the cavity optics and spectrometers) the instrument is designed to measure NO3, N2O5 (by detection of NO3 after thermal dissociation of N2O5), H2O and NO2 by characterising the wavelength dependent optical attenuation within ambient samples by molecular absorption around 662 nm (NO3 and H2O) and 445 nm (NO2). This paper reports novel advancements in BBCEAS instrumentation including a refined method for performing BBCEAS mirror reflectivity calibrations using measurements of the phase delay introduced by the optical cavities to amplitude modulated radiation. Furthermore, a new methodology is introduced for fitting the strong but unresolved transitions of water vapour, which is required for accurate retrieval of water absorption features from the 662 nm absorption band used to measure NO3 concentrations. The paper also details the first example of airborne measurements of NO3, N2O5 and NO2 over Europe from a flight over the North Sea and Thames Estuary on the night of the 20 July 2010, one of the most polluted days of the RONOCO summertime flying period. As part of this analysis, the performance of the BBCEAS instrument is assessed by comparing airborne NO2 measurements to those reported concurrently by a photolytic chemiluminescence based detector.

scholarly journals The development and evaluation of airborne in situ N<sub>2</sub>O and CH<sub>4</sub> sampling using a quantum cascade laser absorption spectrometer (QCLAS)

2016 ◽  
Vol 9 (1) ◽  
pp. 63-77 ◽  
Author(s):  
J. R. Pitt ◽  
M. Le Breton ◽  
G. Allen ◽  
C. J. Percival ◽  
M. W. Gallagher ◽  
...  
Keyword(s):  
Quantum Cascade Laser ◽  
Ambient Pressure ◽  
Calibration Procedure ◽  
Atmospheric Measurements ◽  
Quantum Cascade ◽  
Laser Absorption ◽  
Influence Of Water ◽  
Research Aircraft ◽  
Potential Case ◽  
Absorption Spectrometer

Abstract. Spectroscopic measurements of atmospheric N2O and CH4 mole fractions were made on board the FAAM (Facility for Airborne Atmospheric Measurements) large atmospheric research aircraft. We present details of the mid-infrared quantum cascade laser absorption spectrometer (QCLAS, Aerodyne Research Inc., USA) employed, including its configuration for airborne sampling, and evaluate its performance over 17 flights conducted during summer 2014. Two different methods of correcting for the influence of water vapour on the spectroscopic retrievals are compared and evaluated. A new in-flight calibration procedure to account for the observed sensitivity of the instrument to ambient pressure changes is described, and its impact on instrument performance is assessed. Test flight data linking this sensitivity to changes in cabin pressure are presented. Total 1σ uncertainties of 2.47 ppb for CH4 and 0.54 ppb for N2O are derived. We report a mean difference in 1 Hz CH4 mole fraction of 2.05 ppb (1σ =  5.85 ppb) between in-flight measurements made using the QCLAS and simultaneous measurements using a previously characterised Fast Greenhouse Gas Analyser (FGGA, Los Gatos Research, USA). Finally, a potential case study for the estimation of a regional N2O flux using a mass balance technique is identified, and the method for calculating such an estimate is outlined.

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