scholarly journals Ground-based Fourier transform infrared (FTIR) O<sub>3</sub> retrievals from the 3040 cm<sup>−1</sup> spectral range at Xianghe, China

2020 ◽  
Vol 13 (10) ◽  
pp. 5379-5394
Author(s):  
Minqiang Zhou ◽  
Pucai Wang ◽  
Bavo Langerock ◽  
Corinne Vigouroux ◽  
Christian Hermans ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Spectral Range ◽  
Systematic Uncertainty ◽  
Indium Antimonide ◽  
Degrees Of Freedom ◽  
Estimation Method ◽  
Fourier Transform Infrared ◽  
Atmospheric Composition ◽  
Retrieval Strategy ◽  
Vertical Range

Abstract. In this study, we present O3 retrievals from ground-based Fourier transform infrared (FTIR) solar absorption measurements between June 2018 and December 2019 at Xianghe, China (39.75∘ N, 116.96∘ E). The FTIR spectrometer at Xianghe is operated with indium gallium arsenide (InGaAs) and indium antimonide (InSb) detectors, recording the spectra between 1800 and 11 000 cm−1. As the harmonized FTIR O3 retrieval strategy (Vigouroux et al., 2015) within the Network for the Detection of Atmospheric Composition Change (NDACC) uses the 1000 cm−1 spectral range, we apply the O3 retrieval in the 3040 cm−1 spectral range at Xianghe. The retrieved O3 profile is mainly sensitive to the vertical range between 10 and 40 km, and the degrees of freedom for signal is 2.4±0.3 (1σ), indicating that there are two individual pieces of information in partial columns between the surface and 20 km and between 20 and 40 km. According to the optimal estimation method, the systematic and random uncertainties of the FTIR O3 total columns are about 13.6 % and 1.4 %, respectively. The random uncertainty is consistent with the observed daily standard deviation of the FTIR retrievals. To validate the FTIR O3 total and partial columns, we apply the same O3 retrieval strategy at Maïdo, Réunion (a.k.a. Reunion Island; 21.08∘ N, 55.38∘ E). The FTIR O3 (3040 cm−1) measurements at Xianghe and Maïdo are then compared with the nearby ozonesondes at Beijing (39.81∘ N, 116.47∘ E) and at Gillot (20.89∘ S, 55.53∘ E), respectively, as well as with co-located TROPOspheric Monitoring Instrument (TROPOMI) satellite measurements at both sites. In addition at Maïdo, we compare the FTIR O3 (3040 cm−1) retrievals with the standard NDACC FTIR O3 measurements using the 1000 cm−1 spectral range. It was found that the total columns retrieved from the FTIR O3 3040 cm−1 measurements are underestimated by 5.5 %–9.0 %, which is mainly due to the systematic uncertainty in the partial column between 20 and 40 km (about −10.4 %). The systematic uncertainty in the partial column between surface and 20 km is relatively small (within 2.4 %). By comparison with other measurements, it was found that the FTIR O3 (3040 cm−1) retrievals capture the seasonal and synoptic variations of the O3 total and two partial columns very well. Therefore, the ongoing FTIR measurements at Xianghe can provide useful information on the O3 variations and (in the future) long-term trends.

scholarly journals Ground-based FTIR O<sub>3</sub> retrievals from the 3040 cm<sup>−1</sup> spectral range at Xianghe, China

2020 ◽  
Author(s):  
Minqiang Zhou ◽  
Pucai Wang ◽  
Bavo Langerock ◽  
Corinne Vigouroux ◽  
Christian Hermans ◽  
...  
Keyword(s):  
Indium Gallium Arsenide ◽  
Spectral Range ◽  
Systematic Uncertainty ◽  
Indium Antimonide ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Atmospheric Composition ◽  
Retrieval Strategy ◽  
Solar Absorption ◽  
Vertical Range

Abstract. In this study, we present O3 retrievals from ground-based Fourier-transform infrared (FTIR) solar absorption measurements between June 2018 and December 2019 at Xianghe, China (39.75° N, 116.96° E). The FTIR spectrometer at Xianghe is operated with indium gallium arsenide (InGaAs) and indium antimonide (InSb) detectors, recording the spectra between 1800 and 11000 cm−1. As the harmonized FTIR O3 retrieval strategy (Vigouroux et al., 2015) within the Network for the Detection of Atmospheric Composition Change (NDACC) uses the 1000 cm−1 spectral range, we designed an alternative O3 retrieval strategy in the 3040 cm−1 spectral range at Xianghe. The retrieved O3 profile is mainly sensitive to the vertical range between 5 and 40 km, and the degree of freedom for signal is 2.4 ± 0.3 (1σ), indicating that there are two individual pieces of information in partial columns between the surface and 20 km and between 20 and 40 km. According to the optimal estimation method, the systematic and random uncertainties of the FTIR O3 total columns are about 13.6 % and 1.4 %, respectively. The random uncertainty is consistent with the observed daily standard deviation of the FTIR retrievals. To validate the FTIR O3 total and partial columns, we apply the same O3 retrieval strategy at Maïdo, Reunion Island (21.08° N, 55.38° E). The FTIR O3 (3040 cm−1) measurements at Xianghe and Maïdo are then compared with the nearby ozonesondes at Beijing (39.81° N, 116.47° E) and at Gillot (20.89° S, 55.53° E), respectively, as well as with co-located TROPOspheric Monitoring Instrument (TROPOMI) satellite measurements at both sites. In addition, at Maïdo, we compare the FTIR O3 (3040 cm−1) retrievals with the standard NDACC FTIR O3 measurements using the 1000 cm−1 spectral range. It is found that the total columns retrieved from the FTIR O3 3040 cm−1 measurements are underestimated by 5.5–9.0 %, which is mainly due to the systematic uncertainty in the partial column between 20 and 40 km (about −10.4 %). The systematic uncertainty in the partial column between surface and 20 km is relatively small (within 2.4 %). By comparison with other measurements, it is found that the FTIR O3 (3040 cm−1) retrievals capture very well the seasonal and synoptic variations of the O3 total and two partial columns. Therefore, the ongoing FTIR measurements at Xianghe can provide useful information on the O3 variations and (in the future) long-term trends.

scholarly journals Characterization and potential for reducing optical resonances in Fourier transform infrared spectrometers of the Network for the Detection of Atmospheric Composition Change (NDACC)

2021 ◽  
Vol 14 (2) ◽  
pp. 1239-1252
Author(s):  
Thomas Blumenstock ◽  
Frank Hase ◽  
Axel Keens ◽  
Denis Czurlok ◽  
Orfeo Colebatch ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Indium Antimonide ◽  
Beam Splitter ◽  
Background Level ◽  
Fourier Transform Infrared ◽  
Air Gap ◽  
Atmospheric Composition ◽  
Composition Change ◽  
Infrared Source ◽  
Optical Resonances

Abstract. Although optical components in Fourier transform infrared (FTIR) spectrometers are preferably wedged, in practice, infrared spectra typically suffer from the effects of optical resonances (“channeling”) affecting the retrieval of weakly absorbing gases. This study investigates the level of channeling of each FTIR spectrometer within the Network for the Detection of Atmospheric Composition Change (NDACC). Dedicated spectra were recorded by more than 20 NDACC FTIR spectrometers using a laboratory mid-infrared source and two detectors. In the indium antimonide (InSb) detector domain (1900–5000 cm−1), we found that the amplitude of the most pronounced channeling frequency amounts to 0.1 ‰ to 2.0 ‰ of the spectral background level, with a mean of (0.68±0.48) ‰ and a median of 0.60 ‰. In the mercury cadmium telluride (HgCdTe) detector domain (700–1300 cm−1), we find even stronger effects, with the largest amplitude ranging from 0.3 ‰ to 21 ‰ with a mean of (2.45±4.50) ‰ and a median of 1.2 ‰. For both detectors, the leading channeling frequencies are 0.9 and 0.11 or 0.23 cm−1 in most spectrometers. The observed spectral frequencies of 0.11 and 0.23 cm−1 correspond to the optical thickness of the beam splitter substrate. The 0.9 cm−1 channeling is caused by the air gap in between the beam splitter and compensator plate. Since the air gap is a significant source of channeling and the corresponding amplitude differs strongly between spectrometers, we propose new beam splitters with the wedge of the air gap increased to at least 0.8∘. We tested the insertion of spacers in a beam splitter's air gap to demonstrate that increasing the wedge of the air gap decreases the 0.9 cm−1 channeling amplitude significantly. A wedge of the air gap of 0.8∘ reduces the channeling amplitude by about 50 %, while a wedge of about 2∘ removes the 0.9 cm−1 channeling completely. This study shows the potential for reducing channeling in the FTIR spectrometers operated by the NDACC, thereby increasing the quality of recorded spectra across the network.

scholarly journals First ground-based Fourier transform infrared (FTIR) spectrometer observations of HFC-23 at Rikubetsu, Japan, and Syowa Station, Antarctica

2021 ◽  
Vol 14 (9) ◽  
pp. 5955-5976
Author(s):  
Masanori Takeda ◽  
Hideaki Nakajima ◽  
Isao Murata ◽  
Tomoo Nagahama ◽  
Isamu Morino ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Fourier Transform Infrared ◽  
In Situ Measurements ◽  
Atmospheric Composition ◽  
Syowa Station ◽  
Spectroscopic Parameters ◽  
Dry Air ◽  
Systematic Uncertainties ◽  
Ftir Spectrometer

Abstract. We have developed a procedure for retrieving atmospheric abundances of HFC-23 (CHF3) with a ground-based Fourier transform infrared (FTIR) spectrometer and analyzed the spectra observed at Rikubetsu, Japan (43.5∘ N, 143.8∘ E), and at Syowa Station, Antarctica (69.0∘ S, 39.6∘ E). The FTIR retrievals were carried out with the SFIT4 retrieval program, and the two spectral windows of 1138.5–1148.0 cm−1 and 1154.0–1160.0 cm−1 in the overlapping ν2 and ν5 vibrational–rotational transition bands of HFC-23 were used to avoid strong H2O absorption features. We considered O3, N2O, CH4, H2O, HDO, CFC-12 (CCl2F2), HCFC-22 (CHClF2), peroxyacetyl nitrate (PAN) (CH3C(O)OONO2), HCFC-141b (CH3CCl2F), and HCFC-142b (CH3CClF2) to be interfering species. Vertical profiles of H2O, HDO, and CH4 are preliminarily retrieved with other independent spectral windows because these profiles may induce large uncertainties in the HFC-23 retrieval. Each HFC-23 retrieval has only one piece of vertical information with sensitivity to HFC-23 in the troposphere and the lower stratosphere. Retrieval errors mainly arise from the systematic uncertainties of the spectroscopic parameters used to obtain HFC-23, H2O, HDO, and CH4 abundances. For comparison between FTIR-retrieved HFC-23 total columns and surface dry-air mole fractions provided by AGAGE (Advanced Global Atmospheric Gases Experiment), FTIR-retrieved HFC-23 dry-air column-averaged mole fractions (XHFC-23) were calculated. The FTIR-retrieved XHFC-23 values at Rikubetsu and Syowa Station have negative biases of −15 % to −20 % and −25 % compared to the AGAGE datasets, respectively. These negative biases might mainly come from systematic uncertainties of HFC-23 spectroscopic parameters. The trend of the FTIR-retrieved XHFC-23 data at Rikubetsu was derived for December to February (DJF) observations, which are considered to represent the background values when an air mass reaching Rikubetsu has the least influence by transport of HFC-23 emissions from nearby countries. The DJF trend of Rikubetsu over the 1997–2009 period is 0.810 ± 0.093 ppt yr−1 (ppt: parts per trillion), which is in good agreement with the trend derived from the annual global mean datasets of the AGAGE 12-box model for the same period (0.820 ± 0.013 ppt yr−1). The DJF trend of Rikubetsu over the 2008–2019 period is 0.928 ± 0.108 ppt yr−1, which is consistent with the trend in the AGAGE in situ measurements at Trinidad Head (41.1∘ N, 124.2∘ W) for the same period (0.994 ± 0.001 ppt yr−1). The trend of the FTIR-retrieved XHFC-23 data at Syowa Station over the 2007–2016 period is 0.819 ± 0.071 ppt yr−1, which is consistent with that derived from the AGAGE in situ measurements at Cape Grim (40.7∘ S, 144.7∘ E) for the same period (0.874 ± 0.002 ppt yr−1). Although there are systematic biases in the FTIR-retrieved XHFC-23 at both sites, these results indicate that ground-based FTIR observations have the capability to monitor the long-term trend of atmospheric HFC-23. If this FTIR measurement technique were extended to other Network for the Detection of Atmospheric Composition Change (NDACC) ground-based FTIR sites around world, the measurements reported from these sites would complement the global AGAGE observations by filling spatial and temporal gaps and may lead to improved insights about changes in regional and global emissions of HFC-23 and its role in global warming.

scholarly journals Fourier transform infrared time series of tropospheric HCN in eastern China: seasonality, interannual variability, and source attribution

2020 ◽  
Vol 20 (9) ◽  
pp. 5437-5456
Author(s):  
Youwen Sun ◽  
Cheng Liu ◽  
Lin Zhang ◽  
Mathias Palm ◽  
Justus Notholt ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Interannual Variability ◽  
Eastern China ◽  
Fourier Transform Infrared ◽  
Atmospheric Composition ◽  
High Spectral Resolution ◽  
Source Attribution ◽  
Solar Absorption ◽  
Back Trajectories ◽  
Mauna Loa

Abstract. We analyzed seasonality and interannual variability of tropospheric hydrogen cyanide (HCN) columns in densely populated eastern China for the first time. The results were derived from solar absorption spectra recorded with a ground-based high-spectral-resolution Fourier transform infrared (FTIR) spectrometer in Hefei (31∘54′ N, 117∘10′ E) between 2015 and 2018. The tropospheric HCN columns over Hefei, China, showed significant seasonal variations with three monthly mean peaks throughout the year. The magnitude of the tropospheric HCN column peaked in May, September, and December. The tropospheric HCN column reached a maximum monthly mean of (9.8±0.78)×1015 molecules cm−2 in May and a minimum monthly mean of (7.16±0.75)×1015 molecules cm−2 in November. In most cases, the tropospheric HCN columns in Hefei (32∘ N) are higher than the FTIR observations in Ny-Ålesund (79∘ N), Kiruna (68∘ N), Bremen (53∘ N), Jungfraujoch (47∘ N), Toronto (44∘ N), Rikubetsu (43∘ N), Izana (28∘ N), Mauna Loa (20∘ N), La Reunion Maido (21∘ S), Lauder (45∘ S), and Arrival Heights (78∘ S) that are affiliated with the Network for Detection of Atmospheric Composition Change (NDACC). Enhancements of tropospheric HCN column were observed between September 2015 and July 2016 compared to the same period of measurements in other years. The magnitude of the enhancement ranges from 5 % to 46 % with an average of 22 %. Enhancement of tropospheric HCN (ΔHCN) is correlated with the concurrent enhancement of tropospheric CO (ΔCO), indicating that enhancements of tropospheric CO and HCN were due to the same sources. The GEOS-Chem tagged CO simulation, the global fire maps, and the potential source contribution function (PSCF) values calculated using back trajectories revealed that the seasonal maxima in May are largely due to the influence of biomass burning in Southeast Asia (SEAS) (41±13.1 %), Europe and boreal Asia (EUBA) (21±9.3 %), and Africa (AF) (22±4.7 %). The seasonal maxima in September are largely due to the influence of biomass burnings in EUBA (38±11.3 %), AF (26±6.7 %), SEAS (14±3.3 %), and North America (NA) (13.8±8.4 %). For the seasonal maxima in December, dominant contributions are from AF (36±7.1 %), EUBA (21±5.2 %), and NA (18.7±5.2 %). The tropospheric HCN enhancement between September 2015 and July 2016 at Hefei (32∘ N) was attributed to an elevated influence of biomass burnings in SEAS, EUBA, and Oceania (OCE) in this period. In particular, an elevated number of fires in OCE in the second half of 2015 dominated the tropospheric HCN enhancement between September and December 2015. An elevated number of fires in SEAS in the first half of 2016 dominated the tropospheric HCN enhancement between January and July 2016.

scholarly journals Thermal Camera-Based Fourier Transform Infrared Thermospectroscopic Imager

2020 ◽  
pp. 000370282097302 ◽  
Author(s):  
Stéphane Chevalier ◽  
Jean-Noël Tourvieille ◽  
Alain Sommier ◽  
Jean-Christophe Batsale ◽  
Bruno Beccard ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Spectral Resolution ◽  
Indium Antimonide ◽  
Thermal Emission ◽  
Fourier Transform Infrared ◽  
Technical Note ◽  
Thermal Camera ◽  
Ir Camera ◽  
New Instrument ◽  
Ft Ir

In this technical note, we present an advanced thermospectroscopic imager based on a Fourier transform infrared (FT-IR) spectrometer and a thermal camera. This new instrument can image both thermal emission and multispectral absorbance fields in a few seconds at a resolution of 4 cm−1 or less. The setup is made of a commercial FT-IR spectrometer (ThermoFisher Nicolet iS50R) synchronized to an IR camera (indium antimonide and strained layer superlattice) as a detector to record the interferograms in each pixel of the images. A fast Fourier transform algorithm with apodization and Mertz phase correction is applied to the images, and the background is rationed to process the interferograms into the absorbance spectra in each pixel. The setup and image processing are validated using thin polystyrene films; during this processing, more than 1750 spectra per second are recorded. A spectral resolution equivalent to that of commercial FT-IR spectrometers is obtained for absorbance peaks valued less than two. The transient capability of the FT-IR thermospectroscopic imager is illustrated by measuring the heterogeneous thermal and absorbance fields during the phase change of paraffin over a few minutes. The complete mechanism of the thermochemical processes during a polymer solidification is revealed through the thermospectroscopic images, demonstrating the usefulness of such an instrument in studying fast transient thermal and chemical phenomena with an improved spectral resolution.

scholarly journals Detection and attribution of wildfire pollution in the Arctic and northern midlatitudes using a network of Fourier-transform infrared spectrometers and GEOS-Chem

2020 ◽  
Vol 20 (21) ◽  
pp. 12813-12851
Author(s):  
Erik Lutsch ◽  
Kimberly Strong ◽  
Dylan B. A. Jones ◽  
Thomas Blumenstock ◽  
Stephanie Conway ◽  
...  
Keyword(s):  
Time Series ◽  
Fourier Transform ◽  
Standard Deviation ◽  
Biomass Burning ◽  
Fourier Transform Infrared ◽  
Atmospheric Composition ◽  
The Arctic ◽  
Back Trajectory ◽  
Pollution Events ◽  
Emission Ratios

Abstract. We present a multiyear time series of column abundances of carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) measured using Fourier-transform infrared (FTIR) spectrometers at 10 sites affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC). Six are high-latitude sites: Eureka, Ny-Ålesund, Thule, Kiruna, Poker Flat, and St. Petersburg, and four are midlatitude sites: Zugspitze, Jungfraujoch, Toronto, and Rikubetsu. For each site, the interannual trends and seasonal variabilities of the CO time series are accounted for, allowing background column amounts to be determined. Enhancements above the seasonal background were used to identify possible wildfire pollution events. Since the abundance of each trace gas emitted in a wildfire event is specific to the type of vegetation burned and the burning phase, correlations of CO to the long-lived wildfire tracers HCN and C2H6 allow for further confirmation of the detection of wildfire pollution. A GEOS-Chem tagged CO simulation with Global Fire Assimilation System (GFASv1.2) biomass burning emissions was used to determine the source attribution of CO concentrations at each site from 2003 to 2018. For each detected wildfire pollution event, FLEXPART back-trajectory simulations were performed to determine the transport times of the smoke plume. Accounting for the loss of each species during transport, the enhancement ratios of HCN and C2H6 with respect to CO were converted to emission ratios. We report mean emission ratios with respect to CO for HCN and C2H6 of 0.0047 and 0.0092, respectively, with a standard deviation of 0.0014 and 0.0046, respectively, determined from 23 boreal North American wildfire events. Similarly, we report mean emission ratios for HCN and C2H6 of 0.0049 and 0.0100, respectively, with a standard deviation of 0.0025 and 0.0042, respectively, determined from 39 boreal Asian wildfire events. The agreement of our emission ratios with literature values illustrates the capability of ground-based FTIR measurements to quantify biomass burning emissions. We provide a comprehensive dataset that quantifies HCN and C2H6 emission ratios from 62 wildfire pollution events. Our dataset provides novel emission ratio estimates, which are sparsely available in the published literature, particularly for boreal Asian sources.

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