scholarly journals Long open path measurements of greenhouse gases in air using near infrared Fourier transform spectroscopy

2017 ◽  
Author(s):  
David W. T. Griffith ◽  
Denis Pöhler ◽  
Stefan Schmitt ◽  
Samuel Hammer ◽  
Sanam N. Vardag ◽  
...  
Keyword(s):  
Near Infrared ◽  
Measurement Techniques ◽  
Trace Gas ◽  
Small Scale ◽  
Gas Composition ◽  
Spatial Averaging ◽  
Mid Infrared ◽  
Open Path ◽  
Atmospheric Trace Gas

Abstract. In complex and urban environments, atmospheric trace gas composition is highly variable in time and space. Point measurement techniques for trace gases with in situ instruments are well established and accurate, but do not provide spatial averaging to compare against developing high resolution atmospheric models of composition and small scale meteorology with resolutions of the order of a kilometre. Open path measurement techniques provide path average concentrations and spatial averaging which, if sufficiently accurate, may be better suited to assessment and interpretation with such models. Open path Fourier Transform Spectroscopy (FTS) in the mid infrared region, and Differential Optical Absorption Spectroscopy (DOAS) in the UV and visible, have been used for many years for open path spectroscopic measurements of selected species in both clean air and in polluted environments. Compared to the mid infrared, near infrared instrumentation allows measurements over longer paths than mid IR FTS, for species such as greenhouse gases which are not easily accessible to DOAS. In this pilot study we present the first open path near infrared (4000–10 000 cm−1, 1.0–2.5 μm) FTS measurements of CO2, CH4, O2, H2O and HDO over a 1.5 km path in urban Heidelberg, Germany. We describe the construction of the open path FTS system, the analysis of the collected spectra, precision and accuracy of the measurements, and the results from a four-month trial measurement period in July–November 2014. The open path measurements are compared to calibrated in situ measurements made at one end of the open path. There are small but significant differences between in situ and open path measurements coincident in time which reflect local sources and sinks and the way in which they are sampled by the point and path-averaged measurements. Open path FTS may provide a valuable new tool for investigations of atmospheric trace gas composition in complex, small scale environments such as cities.

scholarly journals Long open-path measurements of greenhouse gases in air using near-infrared Fourier transform spectroscopy

2018 ◽  
Vol 11 (3) ◽  
pp. 1549-1563 ◽  
Author(s):  
David W. T. Griffith ◽  
Denis Pöhler ◽  
Stefan Schmitt ◽  
Samuel Hammer ◽  
Sanam N. Vardag ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Near Infrared ◽  
Measurement Techniques ◽  
Trace Gas ◽  
Gas Composition ◽  
Spatial Averaging ◽  
Mid Infrared ◽  
Open Path ◽  
Atmospheric Trace Gas

Abstract. In complex and urban environments, atmospheric trace gas composition is highly variable in time and space. Point measurement techniques for trace gases with in situ instruments are well established and accurate, but do not provide spatial averaging to compare against developing high-resolution atmospheric models of composition and meteorology with resolutions of the order of a kilometre. Open-path measurement techniques provide path average concentrations and spatial averaging which, if sufficiently accurate, may be better suited to assessment and interpretation with such models. Open-path Fourier transform spectroscopy (FTS) in the mid-infrared region, and differential optical absorption spectroscopy (DOAS) in the UV and visible, have been used for many years for open-path spectroscopic measurements of selected species in both clean air and in polluted environments. Near infrared instrumentation allows measurements over longer paths than mid-infrared FTS for species such as greenhouse gases which are not easily accessible to DOAS.In this pilot study we present the first open-path near-infrared (4000–10 000 cm−1, 1.0–2.5 µm) FTS measurements of CO2, CH4, O2, H2O and HDO over a 1.5 km path in urban Heidelberg, Germany. We describe the construction of the open-path FTS system, the analysis of the collected spectra, several measures of precision and accuracy of the measurements, and the results a four-month trial measurement period in July–November 2014. The open-path measurements are compared to calibrated in situ measurements made at one end of the open path. We observe significant differences of the order of a few ppm for CO2 and a few tens of ppb for CH4 between the open-path and point measurements which are 2 to 4 times the measurement repeatability, but we cannot unequivocally assign the differences to specific local sources or sinks. We conclude that open-path FTS may provide a valuable new tool for investigations of atmospheric trace gas composition in complex, small-scale environments such as cities.

scholarly journals Performance of an open-path near-infrared measurement system for measurements of CO<sub>2</sub> and CH<sub>4</sub> during extended field trials

2021 ◽  
Vol 14 (4) ◽  
pp. 3119-3130
Author(s):  
Nicholas M. Deutscher ◽  
Travis A. Naylor ◽  
Christopher G. R. Caldow ◽  
Hamish L. McDougall ◽  
Alex G. Carter ◽  
...  
Keyword(s):  
Near Infrared ◽  
In Situ Measurements ◽  
Point Sources ◽  
Atmospheric Composition ◽  
Small Scale ◽  
Open Path ◽  
Local Point ◽  
Extended Field ◽  
Measurement Repeatability

Abstract. Open-path measurements of atmospheric composition provide spatial averages of trace gases that are less sensitive to small-scale variations and the effects of meteorology. In this study we introduce improvements to open-path near-infrared (OP-NIR) Fourier transform spectrometer measurements of CO2 and CH4. In an extended field trial, the OP-NIR achieved measurement repeatability 6 times better for CO2 (0.28 ppm) and 10 times better for CH4 (2.1 ppb) over a 1.55 km one-way path than its predecessor. The measurement repeatability was independent of path length up to 1.55 km, the longest distance tested. Comparisons to co-located in situ measurements under well-mixed conditions characterise biases of 1.41 % for CO2 and 1.61 % for CH4 relative to in situ measurements calibrated to World Meteorological Organisation – Global Atmosphere Watch (WMO-GAW) scales. The OP-NIR measurements can detect signals due to local photosynthesis and respiration, and local point sources of CH4. The OP-NIR is well-suited for deployment in urban or rural settings to quantify atmospheric composition on kilometre scales.

scholarly journals Performance of an open-path near infrared measurement system for measurements of CO<sub>2</sub> and CH<sub>4</sub> during extended field trials

2020 ◽  
Author(s):  
Nicholas M. Deutscher ◽  
Travis A. Naylor ◽  
Christopher G. R. Caldow ◽  
Hamish L. McDougall ◽  
Alex G. Carter ◽  
...  
Keyword(s):  
Near Infrared ◽  
In Situ Measurements ◽  
Point Sources ◽  
Atmospheric Composition ◽  
Small Scale ◽  
Open Path ◽  
Local Point ◽  
Extended Field ◽  
Measurement Repeatability

Abstract. Open-path measurements of atmospheric composition provide spatial averages of trace gases that are less sensitive to small-scale variations and the effects of meteorology. In this study we introduce improvements to Open-Path Near Infrared (OP-NIR) Fourier Transform Spectrometer measurements of CO2 and CH4. In an extended field trial, the OP-NIR achieved measurement repeatability six times better for CO2 (0.26 ppm) and ten times better for CH4 (2.0 ppb) over a 1.55 km one-way path than its predecessor. The measurement repeatability was independent of pathlength up to 1.55 km, the longest distance tested. Comparisons to co-located in situ measurements under well-mixed conditions characterise biases of 2.67 % for CO2 and 2.46 % for CH4 relative to in situ measurements calibrated to World Meteorological Organisation – Global Atmosphere Watch (WMO-GAW) scales. The OP-NIR measurements can detect signals due to local photosynthesis and respiration, and local point sources of CH4. The OP-NIR is well-suited for deployment in urban or rural settings to quantify atmospheric composition on kilometre scales.

Research on Open-Path Detection for Atmospheric Trace Gas CO Based on TDLAS

2015 ◽  
Vol 42 (2) ◽  
pp. 0215003 ◽  
Author(s):  
姚路 Yao Lu ◽  
刘文清 Liu Wenqing ◽  
刘建国 Liu Jianguo ◽  
阚瑞峰 Kan Ruifeng ◽  
许振宇 Xu Zhenyu ◽  
...  
Keyword(s):  
Trace Gas ◽  
Open Path ◽  
Atmospheric Trace Gas ◽  
Path Detection

Mobile system for open-path trace gas detection in the mid-infrared using a Raman-shifted Cr:LiSAF source

1999 ◽  
Author(s):  
Paula R. Wamsley ◽  
Carl S. Weimer ◽  
Jeffrey T. Applegate ◽  
Stuart P. Beaton ◽  
Brian S. Beyer
Keyword(s):  
Gas Detection ◽  
Trace Gas ◽  
Mobile System ◽  
Trace Gas Detection ◽  
Mid Infrared ◽  
Open Path

Shot-noise-limited dual-beam detector for atmospheric trace-gas monitoring with near-infrared diode lasers

2000 ◽  
Vol 39 (30) ◽  
pp. 5609 ◽  
Author(s):  
Georges Durry ◽  
Ivan Pouchet ◽  
Nadir Amarouche ◽  
Théodore Danguy ◽  
Gerard Megie
Keyword(s):  
Shot Noise ◽  
Near Infrared ◽  
Diode Lasers ◽  
Trace Gas ◽  
Gas Monitoring ◽  
Dual Beam ◽  
Atmospheric Trace Gas

scholarly journals Emissions of trace gases from Australian temperate forest fires: emission factors and dependence on modified combustion efficiency

2017 ◽  
Author(s):  
Elise-Andrée Guérette ◽  
Clare Paton-Walsh ◽  
Maximilien Desservettaz ◽  
Thomas E. L. Smith ◽  
Liubov Volkova ◽  
...  
Keyword(s):  
Forest Fires ◽  
Temperate Forest ◽  
Combustion Efficiency ◽  
Emission Factors ◽  
Trace Gas ◽  
Airborne Measurements ◽  
Trace Gas Emissions ◽  
Open Path ◽  
Modified Combustion Efficiency

Abstract. We characterised trace gas emissions from Australian temperate forest fires through a mixture of in situ open-path FTIR measurements spectroscopy and selective ion flow tube mass spectrometry (SIFT-MS) and White cell FTIR spectroscopy of grab samples. We report emission factors for a total of 25 trace gas species measured in smoke from nine prescribed fires. We find significant dependence on modified combustion efficiency (MCE) for some species, although regional differences indicate that the use of MCE as a proxy may be limited. We also find that the fire-integrated MCE values derived from our in situ on-the-ground open-path measurements are not significantly different from those reported for airborne measurements of smoke from fires in the same ecosystem. We then compare our average emission factors to those measured for fires in North American temperate ecosystems and for fires in Australian savanna and find that, although emission factors of some species agree within 20 %, others differ by a factor of 2 or more. This indicates that the use of ecosystem-specific emission factors is warranted for applications involving emissions from Australian forest fires.

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