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Monitoring the atmospheric concentrations of the greenhouse gases (GHG) carbon dioxide (CO2) and methane (CH4) is a key ingredient for fostering our understanding of the mechanisms behind the sources and sinks of these gases and for verifying and quantitatively attributing their anthropogenic emissions. Here, we present the instrumental setup and performance evaluation of an open-path GHG observatory in the city of Heidelberg, Germany. The observatory measures path-averaged concentrations of CO2 and CH4 along a 1.55 km path in the urban boundary layer above the city. We combine these open-path data with local in situ measurements to evaluate the representativeness of these observation types on the kilometer scale. This representativeness is necessary to accurately quantify emissions, since atmospheric models tasked with this job typically operate on kilometer-scale horizontal grids. For the operational period between 8 February and 11 July 2023, we find a precision of 2.7 ppm (0.58 %) and 18 ppb (0.89 %) for the dry-air mole fractions of CO2 (xCO2) and CH4 (xCH4) in 5 min measurements, respectively. After bias correction, the open-path measurements show excellent agreement with the local in situ data under atmospheric background conditions. Both datasets show clear signals of traffic CO2 emissions in the diurnal xCO2 cycle. However, there are particular situations, such as under southeasterly wind conditions, in which the in situ and open-path data reveal distinct differences up to 20 ppm in xCO2 , most likely related to their different sensitivity to local emission and transport patterns. Our setup is based on a Bruker IFS 125HR Fourier transform spectrometer, which offers a spacious and modular design providing ample opportunities for future refinements of the technique with respect to finer spectral resolution and wider spectral coverage to provide information on gases such as carbon monoxide and nitrogen dioxide. [ABSTRACT FROM AUTHOR]

Mapping the greenhouse gases (GHGs) carbon dioxide (CO 2) and methane (CH 4) above source regions such as urban areas can deliver insights into the distribution and dynamics of local emission patterns. Here, we present the prototype development and an initial performance evaluation of a portable spectrometer that allows for measuring CO 2 and CH 4 concentrations integrated along a long (>10 km) horizontal path component through the atmospheric boundary layer above a target region. To this end, the spectrometer is positioned at an elevated site from which it points downward at reflection targets in the region, collecting the reflected sunlight at shallow viewing angles. The path-integrated CO 2 and CH 4 concentrations are inferred from the absorption fingerprint in the shortwave–infrared (SWIR) spectral range. While mimicking the concept of the stationary California Laboratory for Atmospheric Remote Sensing – Fourier Transform Spectrometer (CLARS-FTS) in Los Angeles, our portable setup requires minimal infrastructure and is straightforward to duplicate and to operate in various locations. For performance evaluation, we deployed the instrument, termed EM27/SCA, side by side with the CLARS-FTS at the Mt. Wilson Observatory (1670 m a.s.l.) above Los Angeles for a 1-month period in April/May 2022. We determined the relative precision of the retrieved slant column densities (SCDs) for urban reflection targets to be 0.36 %–0.55 % for O 2 , CO 2 and CH 4 , where O 2 is relevant for light path estimation. For the partial vertical column (VCD) below instrument level, which is the quantity carrying emission information, the propagated precision errors amount to 0.75 %–2 % for the three gases depending on the distance to the reflection target and solar zenith angle. The comparison to simultaneous CLARS-FTS measurements shows good consistency, but the observed diurnal patterns highlight the need to take light scattering into account to enable detection of emission patterns. [ABSTRACT FROM AUTHOR]

Many industrial combustion emissions may be detected and quantified using imaging Fourier transform spectrometers (IFTSs). Unlike a conventional infrared camera, which generates a single image integrated over a spectrum, IFTSs generate a datacube of images, each at a distinct wavenumber. The resulting intensity spectra may be used to identify the species within the plume and map their column density estimates. However, these estimates can only be interpreted properly in the context of uncertainty, some of which arises from measurement noise. This work uses Bayesian inference to propagate spectral intensity measurement noise into column density estimate uncertainty. Two distinct models for measurement noise are presented and discussed: the signal-dependant Poisson–Gaussian noise model, and the noise-equivalent spectral radiance. The measurement noise is propagated through the inference and the species density quantification model to obtain density uncertainty estimates for carbon dioxide and methane releases in a laboratory experiment. • Imaging Fourier transform spectrometers may be used for gas species quantification. • IFTSs generate mid-wavelength hyperspectral images in the form of spectral datacubes. • CO 2 and CH 4 are released from a heated vent and an IFTS measurement is carried out. • The IFTS sensor noise equivalent spectra radiance (NESR) distribution is derived. • A Bayesian error model based on NESR is used to infer the species column density pdfs. [ABSTRACT FROM AUTHOR]

Accurate monitoring of atmospheric carbon dioxide (CO2) is of great significance for studying the carbon cycle. Compared to ground observational sites, airborne observations cover a wider area, which help in effectively monitoring the distribution of CO2 sources and sinks. In this study, an airborne campaign was carried out in June and July 2021 to measure the atmospheric CO2 concentration over a desert site, Dunhuang, located in western China. The dry-air column-averaged CO2 mole fraction (XCO2) inversion results obtained from the Atmospheric Carbon Dioxide Lidar (ACDL) system were compared with the Orbiting Carbon Observatory 2 (OCO-2) retrievals, portable Fourier Transform Spectrometer (EM27/SUN) measurement results, and with the XCO2 estimates derived using the airborne Ultraportable Greenhouse Gas Analyzer (UGGA) and the Copernicus Atmosphere Monitoring Service (CAMS) model measurements. Moreover, the vertical CO2 profiles obtained from the OCO-2 and the CAMS datasets were also compared with the airborne UGGA measurements. OCO-2 and CAMS CO2 measurements showed a vertical distribution pattern similar to that of the aircraft-based measurements of atmospheric CO2. In addition, the relationship of atmospheric CO2 with the aerosol optical depth (AOD) was also determined and the results showed a strong and positive correlation between the two variables. [ABSTRACT FROM AUTHOR]

A method that makes polymer sheets partially thinner with continuous-wave carbon dioxide (CO2) lasers has been developed. This method can create thin polymer films by attaching the polymer sheets to the copper base by vacuum suction through the holes in the base. Applying the method to polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and polytetrafluoroethylene (PTFE), the thin-film formation is confirmed in PP, PET, and PS but not PTFE. These polymers have the similar thermal properties. PP, PET, and PS show fluidity with increased temperature, but PTFE does not have fluidity. These characteristics of the polymers indicate that the fluidity of polymer is the important characteristic for film formation. The experiments with PP and PET sheets of different thickness show that thicker sheets make thicker films. The fluid flow of the molten polymer is considered to form the thin film at the bottom of the groove made by laser scribing. The numerical simulation of the 2D thermal model also indicates the week cooling effects of the base on the film formation and importance of polymer fluidity. The results of Fourier transform infrared spectrometer (FT-IR) show thermal degradation of the films. To decrease the heat's effect on the films, the polymer sheets should be processed at the highest laser-beam scanning speed that can make thin films. [ABSTRACT FROM AUTHOR]

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 CO 2 and CH 4. In an extended field trial, the OP-NIR achieved measurement repeatability 6 times better for CO 2 (0.28 ppm) and 10 times better for CH 4 (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 CO 2 and 1.61 % for CH 4 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 CH 4. The OP-NIR is well-suited for deployment in urban or rural settings to quantify atmospheric composition on kilometre scales. [ABSTRACT FROM AUTHOR]

In order to mitigate climate change, it is crucial to understand urban greenhouse gas (GHG) emissions precisely, as more than two-thirds of the anthropogenic GHG emissions worldwide originate from cities. Nowadays, urban emission estimates are mainly based on bottom-up calculation approaches with high uncertainties. A reliable and long-term top-down measurement approach could reduce the uncertainty of these emission inventories significantly. We present the Munich Urban Carbon Column network (MUCCnet), the world's first urban sensor network, which has been permanently measuring GHGs, based on the principle of differential column measurements (DCMs), since summer 2019. These column measurements and column concentration differences are relatively insensitive to vertical redistribution of tracer masses and surface fluxes upwind of the city, making them a favorable input for an inversion framework and, therefore, a well-suited candidate for the quantification of GHG emissions. However, setting up such a stationary sensor network requires an automated measurement principle. We developed our own fully automated enclosure systems for measuring column-averaged CO 2 , CH 4 and CO concentrations with a solar-tracking Fourier transform spectrometer (EM27/SUN) in a fully automated and long-term manner. This also includes software that starts and stops the measurements autonomously and can be used independently from the enclosure system. Furthermore, we demonstrate the novel applications of such a sensor network by presenting the measurement results of our five sensor systems that are deployed in and around Munich. These results include the seasonal cycle of CO 2 since 2015, as well as concentration gradients between sites upwind and downwind of the city. Thanks to the automation, we were also able to continue taking measurements during the COVID-19 lockdown in spring 2020. By correlating the CO 2 column concentration gradients to the traffic amount, we demonstrate that our network is capable of detecting variations in urban emissions. The measurements from our unique sensor network will be combined with an inverse modeling framework that we are currently developing in order to monitor urban GHG emissions over years, identify unknown emission sources and assess how effective the current mitigation strategies are. In summary, our achievements in automating column measurements of GHGs will allow researchers all over the world to establish this approach for long-term greenhouse gas monitoring in urban areas. [ABSTRACT FROM AUTHOR]

Earth system models (ESMs) participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) showed large uncertainties in simulating atmospheric CO 2 concentrations. We utilize the Earth System Model Evaluation Tool (ESMValTool) to evaluate emission-driven CMIP5 and CMIP6 simulations with satellite data of column-average CO 2 mole fractions (XCO 2). XCO 2 time series show a large spread among the model ensembles both in CMIP5 and CMIP6. Compared to the satellite observations, the models have a bias of + 25 to - 20 ppmv in CMIP5 and + 20 to - 15 ppmv in CMIP6, with the multi-model mean biases at + 10 and + 2 ppmv, respectively. The derived mean atmospheric XCO 2 growth rate (GR) of 2.0 ppmv yr -1 is overestimated by 0.4 ppmv yr -1 in CMIP5 and 0.3 ppmv yr -1 in CMIP6 for the multi-model mean, with a good reproduction of the interannual variability. All models capture the expected increase of the seasonal cycle amplitude (SCA) with increasing latitude, but most models underestimate the SCA. Any SCA derived from data with missing values can only be considered an "effective" SCA, as the missing values could occur at the peaks or troughs. The satellite data are a combined data product covering the period 2003–2014 based on the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY)/Envisat (2003–2012) and Thermal And Near infrared Sensor for carbon Observation Fourier transform spectrometer/Greenhouse Gases Observing Satellite (TANSO-FTS/GOSAT) (2009–2014) instruments. While the combined satellite product shows a strong negative trend of decreasing effective SCA with increasing XCO 2 in the northern midlatitudes, both CMIP ensembles instead show a non-significant positive trend in the multi-model mean. The negative trend is reproduced by the models when sampling them as the observations, attributing it to sampling characteristics. Applying a mask of the mean data coverage of each satellite to the models, the effective SCA is higher for the SCIAMACHY/Envisat mask than when using the TANSO-FTS/GOSAT mask. This induces an artificial negative trend when using observational sampling over the full period, as SCIAMACHY/Envisat covers the early period until 2012, with TANSO-FTS/GOSAT measurements starting in 2009. Overall, the CMIP6 ensemble shows better agreement with the satellite data than the CMIP5 ensemble in all considered quantities (XCO 2 , GR, SCA and trend in SCA). This study shows that the availability of column-integral CO 2 from satellite provides a promising new way to evaluate the performance of Earth system models on a global scale, complementing existing studies that are based on in situ measurements from single ground-based stations. [ABSTRACT FROM AUTHOR]

Metal oxide (MOX) sensors are increasingly gaining attention in analytical applications. Their fundamental operation principle is based on conversion reactions of selected molecular species at their semiconducting surface. However, the exact turnover of analyte gas in relation to the concentration has not been investigated in detail to date. In the present study, two optical sensing techniques—luminescence quenching for molecular oxygen and infrared spectroscopy for carbon dioxide and methane—have been coupled for characterizing the behavior of an example semiconducting MOX methane gas sensor integrated into a recently developed low-volume gas cell. Thereby, oxygen consumption during MOX operation as well as the generation of carbon dioxide from the methane conversion reaction could be quantitatively monitored. The latter was analyzed via a direct mid-infrared gas sensor system based on substrate-integrated hollow waveguide (iHWG) technology combined with a portable Fourier transform infrared spectrometer, which has been able to not only detect the amount of generated carbon dioxide but also the consumption of methane during MOX operation. Hence, a method based entirely on direct optical detection schemes was developed for characterizing the actual signal generating processes—here for the detection of methane—via MOX sensing devices via near real-time online analysis. [ABSTRACT FROM AUTHOR]

The flexible mid-infrared hollow waveguide is used as the absorption cell for spectroscopic gas sensing. The low-loss bending shape is proposed to achieve a limit of detection (LOD) of ppb level. Simulation and experimentation demonstrate that the spring-shaped waveguide cell, characterized by a single rotation axis, exhibits reduced loss compared to the bending shapes with variable axes. The loss properties were comprehensively analyzed, and the loss spectra were measured using a Fourier transform infrared spectrometer (FTIR) system. To assess the practical application of the proposed spring-shaped waveguide cell, a CO 2 sensing system was established employing a low-cost broad-spectrum source and Fabry-Pérot (FP) pyroelectric detector. The fabricated waveguide cell has an inner diameter (ID) of 2 mm and a length of 119 cm. Experimental results show that the limit of detection (LOD) as low as 349 ppb is achieved, and further improvement can be obtained by increasing the ID. With a weight of merely 2.24 g and a radius of 5 cm, the spring-shaped hollow waveguide represents the most compact and portable waveguide gas cell to our best knowledge. The robustness of the spring-shaped waveguide cell to pitch allows for flexible changes in length and curvature radius, thereby facilitating easy adjustment of sensitivity and size without requiring the custom-made frames. Moreover, the hollow nature of the spring design significantly overcomes the space limitation, further enhancing the practicality of the waveguide cell. [Display omitted] • The loss properties of low-loss hollow waveguide cells with various bending shapes were discussed. • The spring-shaped waveguide cell shows the best property for application as gas absorption cell. • A miniaturized, low-cost CO 2 gas sensing system was established and the limit of detection (LOD) of 349 ppb was achieved. [ABSTRACT FROM AUTHOR]

• A near infrared all-fiber structure LHR with a spectral resolution of 0.09 cm−1 was developed. • The variation of CO 2 column concentration was continuously monitored. • The average measurements precision for the developed LHR is estimated to be about 1.6%. • The observation results for the LHR agree well with those of GOSAT and the ground-based Fourier transform spectrometer. We report a laser heterodyne radiometer (LHR) using a distributed feedback (DFB) diode laser operating in the near infrared region as the local oscillator to continuously measure atmospheric carbon dioxide (CO 2) column concentration, which has a spectral resolution of 0.09 cm−1. The measurements for three consecutive days show that the averaged CO 2 column concentration are 411.5 ppm, 410.4 ppm and 409.5 ppm, respectively. The averaged measurement precision is 1.6% by analyzing the standard deviation of CO 2 column concentration. The relative error of 0.3% is estimated by comparing to CO 2 average column concentration derived from GOSAT data on October 31, 2018 during the same measurement period. Moreover, the CO 2 results are in good agreement with those measured by the ground-based Fourier transform spectrometer (FTS) simultaneously. The results prove the capacity and the reliability of the developed near infrared LHR to monitor the time series of regional CO 2. [ABSTRACT FROM AUTHOR]

High-resolution, laboratory, absorption spectra of the a1Δg←X3Σg- oxygen (O2) band measured using cavity ring-down spectroscopy were fitted using the Voigt and speed-dependent Voigt line shapes. We found that the speed-dependent Voigt line shape was better able to model the measured absorption coefficients than the Voigt line shape. We used these line shape models to calculate absorption coefficients to retrieve atmospheric total columns abundances of O2 from ground-based spectra from four Fourier transform spectrometers that are a part of the Total Carbon Column Observing Network (TCCON). Lower O2 total columns were retrieved with the speed-dependent Voigt line shape, and the difference between the total columns retrieved using the Voigt and speed-dependent Voigt line shapes increased as a function of solar zenith angle. Previous work has shown that carbon dioxide (CO2) total columns are better retrieved using a speed-dependent Voigt line shape with line mixing. The column-averaged dry-air mole fraction of CO2 (XCO2) was calculated using the ratio between the columns of CO2 and O2 retrieved (from the same spectra) with both line shapes from measurements taken over a 1-year period at the four sites. The inclusion of speed dependence in the O2 retrievals significantly reduces the air mass dependence of XCO2 , and the bias between the TCCON measurements and calibrated integrated aircraft profile measurements was reduced from 1 % to 0.4 %. These results suggest that speed dependence should be included in the forward model when fitting near-infrared CO2 and O2 spectra to improve the accuracy of XCO2 measurements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bruker IFS 125 HR Fourier transform spectrometer with LED light source and optical path length of about 1 km reaches the sensitivity of 1.23 × 10-10 cm−1 near 660 nm. • First observation of the 3005 i − 00,001 (i = 2,3) and 60031–00001 absorption bands of 12C16O 2 near 660 nm. • Measured line positions and intensities of the 3005 i − 00,001 (i = 2,3) and 60031–00001 bands of 12C16O 2. • HITRAN2020 line parameters for the studied bands should be updated. The absorption spectra of carbon dioxide were recorded in the region from 15,000 to 15,300 cm−1, using a Bruker IFS 125 HR Fourier transform spectrometer and a 30 m multipass cell with the White type optical system. The recording was performed at a spectral resolution of 0.044 – 0.050 cm−1, room temperature, a path length of 1057.95 m and pressures of 185 and 362 mbar. Utilization of a LED as a light source provided a sensitivity (noise equivalent absorption) at the level of k ν = 1.23 × 10-10 cm−1 and allowed detection of a number of lines of two 3005 i − 00001 (i = 2,3) bands and several lines of the 60031 – 00001 band of 12C16O 2 with the intensity values down to 10-30 cm−1/(molecule cm−2) at 296 K. These bands were observed for the first time. The uncertainty of the line position measurements was estimated to be about 0.005 cm−1 for the unblended lines with a high signal-to-noise ratio. The uncertainties of the retrieved line intensities for the strongest unblended lines are at the level of 15 %. The spectroscopic constants for observed bands were fitted to the observed line positions. The vibrational transition dipole moments squared of these bands were fitted to the observed line intensities. The measured line positions were compared to those from the HITRAN2020 database and to those predicted with the global effective Hamiltonian. The measured line intensities were compared to the values from the HITRAN2020 database and from the Ames2021 line list. [ABSTRACT FROM AUTHOR]

CO concentration (XCO) shows the spatial and temporal variation in Iran. The major purpose of this investigation is the assessment of the spatial distribution of carbon dioxide concentration in the different seasons of 2013 based on the Thermal And Near Infrared Sensor for Carbon Observation-Fourier Transform Spectrometer (TANSO-FTS) level 2 GOSAT data by implementing the ordinary kriging (OK) method. In this study, the Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI) data from the MODerate resolution Imaging Spectroradiometer (MODIS), and metrological parameters (temperature and precipitation) were used for the analysis of the spatial distribution of CO over Iran in 2013. The spatial distribution maps of XCO show the highest concentration of this gas in the south and south-east and the lowest concentration in the north and north-west. These results indicate that the concentration of carbon dioxide decreased with the increase of LST and temperature and a decrease of NDVI and humidity in the study area. Therefore, the existence of vegetation has an effective role in capturing carbon from the atmosphere by photosynthesis phenomena, and sustainable land management can be effective for carbon absorption from the atmosphere and mitigation of climate change in arid and semi-arid regions. [ABSTRACT FROM AUTHOR]

The Greenhouse gases Observing SATellite (GOSAT) launched in January 2009 has provided radiance spectra with a Fourier Transform Spectrometer for more than eight years. The Orbiting Carbon Observatory 2 (OCO-2) launched in July 2014, collects radiance spectra using an imaging grating spectrometer. Both sensors observe sunlight reflected from Earth's surface and retrieve atmospheric carbon dioxide (CO2) concentrations, but use different spectrometer technologies, observing geometries, and ground track repeat cycles. To demonstrate the effectiveness of satellite remote sensing for CO2 monitoring, the GOSAT and OCO-2 teams have worked together pre- and post-launch to cross-calibrate the instruments and cross-validate their retrieval algorithms and products. In this work, we first compare observed radiance spectra within three narrow bands centered at 0.76, 1.60 and 2.06 μm, at temporally coincident and spatially collocated points from September 2014 to March 2017. We reconciled the differences in observation footprints size, viewing geometry and associated differences in surface bidirectional reflectance distribution function (BRDF). We conclude that the spectral radiances measured by the two instruments agree within 5% for all bands. Second, we estimated mean bias and standard deviation of column-averaged CO2 dry air mole fraction (XCO2) retrieved from GOSAT and OCO-2 from September 2014 to May 2016. GOSAT retrievals used Build 7.3 (V7.3) of the Atmospheric CO2 Observations from Space (ACOS) algorithm while OCO-2 retrievals used Version 7 of the OCO-2 retrieval algorithm. The mean biases and standard deviations are -0.57 ± 3.33 ppm over land with high gain, -0.17 ± 1.48 ppm over ocean with high gain and -0.19 ± 2.79 ppm over land with medium gain. Finally, our study is complemented with an analysis of error sources: retrieved surface pressure (Psurf), aerosol optical depth (AOD), BRDF and surface albedo inhomogeneity. We found no change in XCO2 bias or standard deviation with time, demonstrating that both instruments are well calibrated. [ABSTRACT FROM AUTHOR]

• The 2005 i - 00001 (i = 1,2) absorption bands of 12C16O 2 revisited. • First observation of the 20053 – 00001absorption band of 12C16O 2. • The first measurements of the line intensities of the 2005 i - 00001 (i = 1,2,3) bands of 12C16O 2. • The HITRAN2020 line parameters for the studied bands should be updated. The absorption spectra of carbon dioxide were recorded in the region from 13,500 to 14,200 cm−1, using a Bruker IFS 125 HR Fourier transform spectrometer and a 30 m multipass cell with the White type optical system. The recording was performed at spectral resolution of 0.03–0.04 cm−1, room temperature, path length of 1057.95 m and at three pressures of 252, 403 and 582 mbar. The achieved sensitivity (noise equivalent absorption) at the level of k ν = 6 × 10−10 cm−1 allowed detection of a number of lines of three 2005 i - 00001 (i = 1,2,3) bands of 12C16O 2 with the intensity values down to 10−29 cm−1/(molecule cm−2) at 296 K. The 20053–00001 band was observed for the first time. The line intensities for all bands were measured for the first time. The uncertainty of the line position measurements was estimated to be about 0.007 cm−1 for the unblended lines with a high value of the signal-to-noise ratio. The uncertainties of the retrieved line intensities for the strongest unblended lines are on the level of 10%. The spectroscopic constants for the three observed bands were fitted to the observed line positions. The vibrational transition dipole moments squared of these bands were fitted to the observed line intensities. A comparison of the measured line positions to those from the HITRAN2020 database was done. Finally a comparison of the measured line intensities to those contained in the HITRAN2020 database as well as in the new version of the Ames line list was also given. [ABSTRACT FROM AUTHOR]

The primary instrument on the Greenhouse gases Observing SATellite (GOSAT) is the Thermal And Near infrared Sensor for carbon Observations (TANSO) Fourier transform spectrometer (FTS). TANSO-FTS uses three shortwave infrared (SWIR) bands to retrieve total columns of CO2 and CH4 along its optical line of sight and one thermal infrared (TIR) channel to retrieve vertical profiles of CO2 and C< volume mixing ratios (VMRs) in the troposphere. We examine version 1 of the TANSO-FTS TIR CH4 product by comparing co-located CH4 VMR vertical profiles from two other remote-sensing FTS systems: the Canadian Space Agency's Atmospheric Chemistry Experiment FTS (ACEFTS) on SCISAT (version 3.5) and the European Space Agency's Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat (ESA ML2PP version 6 and IMK-IAA reduced-resolution version V5R_CH4_224/225), as well as 16 ground stations with the Network for the Detection of Atmospheric Composition Change (NDACC). This work follows an initial inter-comparison study over the Arctic, which incorporated a ground-based FTS at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Canada, and focuses on tropospheric and lowerstratospheric measurements made at middle and tropical latitudes between 2009 and 2013 (mid-2012 for MIPAS). For comparison, vertical profiles from all instruments are interpolated onto a common pressure grid, and smoothing is applied to ACE-FTS, MIPAS, and NDACC vertical profiles. Smoothing is needed to account for differences between the vertical resolution of each instrument and differences in the dependence on a priori profiles. The smoothing operators use the TANSO-FTS a priori and averaging kernels in all cases. We present zonally averaged mean CH4 differences between each instrument and TANSO-FTS with and without smoothing, and we examine their information content, their sensitive altitude range, their correlation, their a priori dependence, and the variability within each data set. Partial columns are calculated from the VMR vertical profiles, and their correlations are examined. We find that the TANSO-FTS vertical profiles agree with the ACE-FTS and both MIPAS retrievals' vertical profiles within 4% (± ~ 40 ppbv) below 15 km when smoothing is applied to the profiles from instruments with finer vertical resolution but that the relative differences can increase to on the order of 25% when no smoothing is applied. Computed partial columns are tightly correlated for each pair of data sets. We investigate whether the difference between TANSO-FTS and other CH4 VMR data products varies with latitude. Our study reveals a small dependence of around 0.1% per 10 degrees latitude, with smaller differences over the tropics and greater differences towards the poles. [ABSTRACT FROM AUTHOR]

Global warming and climate change have been identified as the most important challenges of the 21st century. Greenhouse Gases Observation Satellite ( GOSAT) measures the concentrations of carbon dioxide ( CO2) and methane ( CH4) in the atmosphere column from the earth's surface to the upper atmosphere. In this research, GOSAT Thermal And Near Infrared Sensor for Carbon Observation - Fourier Transform Spectrometer ( TANSO- FTS) level 2 data and meteorological parameters were used in the assessment of changes in CO2 concentration ( XCO2) from 2009 to 2015. We investigated the relationship between XCO2 and meteorological parameters (temperature and precipitation) obtained from weather stations and the Normalized Difference Vegetation Index ( NDVI) in the year 2013 in Iran. The results reveal a steady increase in the mean atmospheric CO2 concentration, from 384.89 to 400.39 ppm. It was observed that the XCO2 varied significantly depending on the month, with the highest concentration of CO2 in April/ May and the lowest concentration in August/ September. The correlation between XCO2 and average monthly air temperature is negative, which means that a reduction in XCO2 with an increase in temperature is dependent on photosynthetic activities in the growing seasons. The highest and lowest correlation coefficient between the NDVI and XCO2 was obtained in the spring and in the fall, respectively. These findings are useful for recognizing factors that affect CO2 concentration in different seasons in arid and semi-arid regions, and as an initial step toward sustainable management. [ABSTRACT FROM AUTHOR]

In this study we introduce a new strategy for the measurement of CO2 distribution in the stratosphere. The proposed experiment is based on an orbiting limb sounder that measures the atmospheric emission within both the thermal infrared (TIR) and far-infrared (FIR) regions. The idea is to exploit the contribution of the pure rotational transitions of molecular oxygen in the FIR to determine the atmospheric fields of temperature and pressure that are necessary to retrieve the distribution of CO2 from its rovibrational transitions in the TIR. The instrument envisaged to test the new strategy is a Fourier transform spectrometer with two output ports hosting a FIR detector devoted to measuring the O2 transitions and a TIR detector devoted to measure the CO2 transitions. Instrumental and observational parameters of the proposed experiment have been defined by exploiting the heritage of both previous studies and operational limb sounders. The performance of the experiment has been assessed with two-dimensional (2-D) retrievals on simulated observations along a full orbit. For this purpose, optimal spectral intervals have been defined using a validated selection algorithm. Both precision and spatial resolution of the obtained CO2 distributions have been taken into account in the results-evaluation process. We show that the O2 spectral features significantly contribute to the performance of CO2 retrievals and that the proposed experiment can determine 2-D distributions of the CO2 volume mixing ratio with precisions of the order of 1 ppmv in the 10-50 km altitude range. The error budget, estimated for the test case of an ideal instrument and neglecting the spectroscopic errors, indicates that, in the 10-50 km altitude range, the total error of the CO2 fields is set by the random component. This is also the case at higher altitudes, provided the retrieval system is able to model the non-local thermal equilibrium conditions of the atmosphere. The best performance is obtained at altitudes between 20 and 50 km, where the vertical resolution ranges from 3 to 5 km, and the horizontal resolution is of the order of 300-350km depending on latitude. [ABSTRACT FROM AUTHOR]

The spectra of O A-band (0.76 μm) and CO near-infrared emissions (1.6 μm) are simulated by the SCIATRAN radiative transfer model (V3.1.23), and compared with those observed by GOSAT-FTS (Greenhouse gases Observing SATellite-Fourier Transform Spectrometer). Systematic deviations between the observed and simulated spectra are found to exist, especially for the O A-band. The discrepancies are characterized by their mean differences averaged over the observed spectral ranges. A correction is applied to the observed GOSAT-FTS L1B (V141.141) spectra by scaling the spectral intensity measured by TANSO-FTS (Thermal and Near infrared Sensor for carbon Observation Fourier Transform Spectrometer) onboard GOSAT. The average columnar CO concentrations (XCO) are retrieved from the observed and the corrected GOSAT-FTS spectra by using the SCIATRAN inversion algorithm. Compared with the GOSAT-FTS L2 XCO data products retrieved from the observed spectra of GOSAT-FTS, the SCIATRAN retrievals from the corrected spectra show a much better agreement, with the relative error less than 1%. But the results of GOSAT TANSO-FTS (V161.160) show smaller residuals than GOSAT TANSO-FTS (V141.141) without mean residual correction. The results indicate that the mean residual correction would increase the precision of XCO retrieval for spectra with systematic deviations. [ABSTRACT FROM AUTHOR]

[Display omitted] • The rotational spectrum of anisole-CO 2 was analyzed. • The complex is characterized by a dominant C···O tetrel bond and two secondary C H ∙∙∙O weak hydrogen bonds. • The network of the cooperative non-covalent interactions in the anisole-CO 2 complex is revealed. Rotational spectrum of the 1:1 anisole-CO 2 complex has been investigated using a pulsed jet Fourier transform microwave spectrometer supplemented with quantum chemical calculations. In the pulsed jet, only one isomer has been observed which is characterized by a dominant C···O tetrel bond and two C H···O CO2 weak hydrogen bonds. Different theoretical methods predict different orders of relative energies of plausible conformations. The experimental observation is most consistent with the theoretical estimation at the B3LYP-D3(BJ)/6–311++G(d,p) level of theory. Johnson's non-covalent interaction, quantum theory of atoms in molecules and natural bond orbital analyses have been applied to better understand the nature of non-covalent interactions at play in the anisole-CO 2 complex. [ABSTRACT FROM AUTHOR]

In total, 521 vibrational–rotational spectral lines of the Δ v = 1 transitions of 69 GaF and 71 GaF up to bands v = 5–4 and 4–3, respectively, were recorded in emission with a Fourier-transform spectrometer at unapodized resolution 0.010 cm −1 in range 625–660 cm −1 . The response of a HgCdTe detector enforced the lower limit, 625 cm −1 . To calibrate accurately the spectral lines, the absorption spectrum of CO 2 was simultaneously recorded, using dual sample cells, to serve as wavenumber standards. A set of 782 spectral lines comprising all present vibrational–rotational spectra of 69 GaF and 71 GaF, the reported laser-diode measurements of the Δ v = 1 band sequence and the reported rotational spectra was subjected to a global multi-isotopologue analysis through fitting with 11 isotopically invariant, irreducible molecular parameters in a single set. Normalized standard deviation 1.093 indicates a satisfactory fit. For the effects of the breakdown of the Born–Oppenheimer approximation on GaF, the values of non-Born–Oppenheimer parameters Δ B Ga , Δ ω Ga and r 1q Ga (= r 1q F ) are experimentally determined for the first time. To facilitate the calculations or predictions of spectral frequencies, the values of the Dunham coefficients of 24 Y ij and 81 band parameters for both 69 GaF and 71 GaF were back-calculated with uncertainties using the 11 evaluated molecular parameters. To date, various types of effective B e , r e , ω e , and k have been reported for GaF. Because, in the present work, Dunham coefficients Y ij are algebraically expressed with the genuine B e , ω e , a i ( i = 1, …) and the non-Born−Oppenheimer correction parameters, the exact expressions for the physical significance of effective quantities are derivable. The various effective quantities of B e , r e , ω e and k calculated with these expressions for the physical significance and the determined values of the fitted parameters of GaF agree satisfactorily with the reported values. The physical significance of the conventional treatments of adiabatic and nonadiabatic corrections for Δ 01 Ga and Δ 10 Ga is discussed. [ABSTRACT FROM AUTHOR]

Solar absorption spectra in the near-infrared region have been continuously acquired with a ground-based (g-b) high-resolution Fourier transform spectrometer (FTS) at Saga, Japan, since July 2011. Column-averaged dry-air mole fractions of greenhouse gases were retrieved from the measured spectra for the period from July 2011 to December 2014. Aircraft measurements of CO2 and CH4 for calibrating the g-b FTS data were performed in January 2012 and 2013, and it is found that the g-b FTS and aircraft data agree to within ± 0.2%. The column-averaged dry-air mole fractions of CO2 and CH4 (XCO2 and XCH4) show increasing trends, with average growth rates of 2.3 and 9.5 ppb yr-1, respectively, during the ~ 3.5 yr of observation. We compared the g-b FTS XCO2 and XCH4 data with those derived from backscattered solar spectra in the short-wavelength infrared (SWIR) region measured with Thermal And Near-infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS) onboard the Greenhouse gases Observing SATellite (GOSAT): NIES SWIR Level 2 products (versions 02.xx). Average differences between TANSO-FTS and g-b FTS data (TANSO-FTS minus g-b FTS) are 0.40 ± 2.51 and -7.6 ± 13.7 ppb for XCO2 and XCH4, respectively. Using aerosol information measured with a sky radiometer at Saga, we found that the differences between the TANSO-FTS and g-b FTS XCO2 data are moderately negatively correlated with aerosol optical thickness and do not depend explicitly on aerosol size. In addition, from several aerosol profiles measured with lidar located right by the g-b FTS, we were able to show that the presence of cirrus clouds tends to cause an overestimation in the TANSO-FTS XCO2 retrieval, while high aerosol loading in the lower troposphere tends to cause an underestimation. [ABSTRACT FROM AUTHOR]

Mixed matrix membranes (MMMs) are synthesized for efficient CO 2 separation released from various anthropogenic sources, which are due to global environmental concerns. The synergetic effect of porous nitrogen-rich, CO 2 -philic filler and polymer in mixed matrix-based membranes (MMMs) can separate CO 2 competent. The development of various loadings of porphyrin poly(N-isopropyl Acryl Amide) (P-NIPAM)as functionalized organic fillers (5–20%) in polysulfone (PSU) through solution casting is carried out followed by the various characterizations including field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), Fourier Transform Infrared Spectrometer(FT-IR) analysis and pure and mixed gas permeations ranging from 2 to 10 bar feed pressure. Due to both organic species interactions in the matrix, well-distributed fillers and homogenous surfaces, and cross-sectional structures were observed due to π-π interactions and Lewis's basic functionalities. The strong affinity of porous nitrogen-rich and CO 2 -philic fillers through gas permeation analysis showed high CO 2 /CH 4 and CO 2 /N 2 gas performance that surpassed Robeson's upper bound limit. Comparatively, MMMs showed improved CO 2 /CH 4 permeabilities from 87.5 ± 0.5 Barrer to 88.2 ± 0.9 Barrer than pure polymer matrix. For CO 2 /N 2 , CO 2 permeabilities improved to 75 ± 0.8 Barrer than pure polymer matrix. For both gas pairs (CO 2 /CH 4 , CO 2 /N 2), respective pureselectivities (84%; 86%) and binary selectivities (85% and 85%)were improved. Various theoretical gas permeation models were used to predict CO 2 permeabilities for MMMs from which the modified Maxwell-Wagner-Sillar model showed the least AARE% of 0.87. The results showed promising results for efficient CO 2 separation due to exceptional functionalized P-PNIPAM affinitive properties. Finally, cost analysis reflected the inflated cost of membranes production for industrial setup using indigenous resources. [Display omitted] • Development of porphyrin poly(N-isopropyl acryl amide) (P-NIPAM) based functionalized organic fillers in Polymer matrix. •Characterizations and CO 2 , CH 4 , and N 2 permeabilities improved by 97%, 82%, and 81%, respectively. •Modified Maxwell-Wagner-Sillar model showed least AARE% of 0.87. [ABSTRACT FROM AUTHOR]

The absorption spectra of carbon dioxide have been recorded in two wavenumber ranges 9250–9500 cm −1 and 10,700–10,860 cm −1 of the near infrared region using a Bruker IFS 125 HR Fourier transform spectrometer and a 30 m multipass cell with the White type optical system. The spectra were recorded at spectral resolution of 0.03 cm −1 , room temperature, path length of 726.7 m and at four pressures ranging from 187 to 674 mbar. The achieved sensitivity (noise equivalent absorption) at the level of k ν =7.2×10 −10 cm −1 allowed detection of numerous new transitions with intensity values down to 5×10 −29 cm/molecule. The respective measurement time is about 20 h. The multispectrum fittings with the Voigt profile were performed to retrieve the line positions and intensities of 12 observed bands. Three hot bands of 12 C 16 O 2 in the 9250–9500 cm −1 region were detected for the first time. The line intensities of 30032−00001 and 30033−00001 bands of 12 C 16 O 2 and of 20032−00001 band of 16 O 12 C 18 O were measured for the first time. The uncertainty of the line position determination is estimated to be about 0.001 cm −1 for the unblended lines with high value of signal-to-noise ratio. The uncertainty of the line intensity determination varies from 5% to 40% depending on the line strength and on extent of line overlapping. The measured line intensities of 30032−00001 and 30033−00001 bands together with those published for the 00051−00001 band were used to fit the effective dipole moment parameters of 12 C 16 O 2 for the Δ P =15 series of transitions, where P =2 V 1 + V 2 +3 V 3 is a polyad number ( V i ( i =1,2,3) are vibrational quantum numbers). The fitted parameters reproduce the measured line intensities within experimental uncertainties. Comparison of the measured line positions and intensities to those contained in HITRAN, GEISA, CDSD and AMES line lists is given. [ABSTRACT FROM AUTHOR]

Because a synoptic overview facilitates understanding of the temporal and spatial changes in the global distribution of greenhouse gases, we developed a statistical spatial estimation method using kriging. Level 3 (L3) data products for the Greenhouse Gases Observing Satellite (GOSAT) Thermal And Near infrared Sensor for Carbon Observation (TANSO) Fourier Transform Spectrometer (FTS) Short Wave Infrared (SWIR) were generated from column-averaged, dry-air mole fractions of carbon dioxide (XCO2) and methane (XCH4) TANSO-FTS SWIR Level 2 (L2) products using this method. Although there have been some reports on the use of kriging for analysing GOSAT products, the kriging method used in this research was specifically adapted to the statistical characteristics of GOSAT L2 products. In the context of using data for atmospheric research, spatially interpolated data (GOSAT L3 products) cannot be more accurate than model-simulated global distributions of gas concentrations (GOSAT Level 4B (L4B) products), which are generated using an atmospheric tracer transport model. However, the L3 product takes much less time to generate than the L4B. It would take about a year to produce the L4B after generation of an L2 product. The great advantage of the L3 product is that it gives a comprehensive and reasonable monthly global distribution of gas concentrations with little delay. The L3 product using the kriging method can be generated on a monthly basis by estimating global semi-variogram curves from the L2 products for each month and interpolating spatially within a region with a radius of 1000 km from existing L2 data locations. The main purpose of this paper is to describe the methodology and characteristics of kriging used to generate the GOSAT L3 product, not for strictly scientific use of the estimated values, but for a reasonable global map of gas concentrations derived statistically from the sparsely observed L2 products within a short time frame. The characteristics of this method are compared to XCO2products simulated with an atmospheric tracer transport model. The results show that the method proposed in this study is of practical use for generating L3 products from L2 products. [ABSTRACT FROM PUBLISHER]

Two most stable of the four structures of CH 3 CN-CO 2 complex, both having a carbon-tetrel bond have been observed by microwave spectroscopy. [Display omitted] • Rotational spectra of the acetonitrile-carbon dioxide complex. • Gas-phase study of a tetrel bonded complex. • Rotational spectra of two conformers of CH 3 CN-CO 2. • T -shaped complex of CH 3 CN-CO 2 bound by N⋯CO 2 tetrel bond. The rotational spectra of the weakly bound acetonitrile-carbon dioxide complex have been recorded using a pulsed-nozzle Fourier transform microwave spectrometer. In a supersonic expansion using helium as the carrier gas, the two lowest energy conformers were observed. A T -shaped structure where the nitrogen end of CH 3 CN donates electron density to the C center of CO 2 , and a slipped-parallel structure where the CO 2 and CH 3 CN are aligned such that the linear heavy atom backbones are parallel. Spectra were also recorded for the CD 3 CN∙∙∙CO 2 and the CH 3 13CN∙∙∙CO 2 isotopologues which help to confirm the structures observed. The spectra show hyperfine splitting due to nitrogen quadrupole coupling which could be resolved. The CH 3 CN∙∙∙CO 2 complex offers the possibility to study the tetrel bond involving the three C atoms of the system. The observed T -shaped structure is bound by a N∙∙∙C carbon/tetrel bond. The Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) analyses are used to identify the non-covalent interactions present in this complex and investigate different types of tetrel bonds. [ABSTRACT FROM AUTHOR]

An algorithm is developed to retrieve the vertical profile of carbon dioxide in the 5 to 25 km altitude range using mid-infrared solar occultation spectra from the main instrument of the ACE (Atmospheric Chemistry Experiment) mission, namely the Fourier transform spectrometer (FTS). The main challenge is to find an atmospheric phenomenon which can be used for accurate tangent height determination in the lower atmosphere, where the tangent heights (THs) calculated from geometric and timing information are not of sufficient accuracy. Error budgets for the retrieval of CO2 from ACE-FTS and the FTS on a potential follow-on mission named CASS (Chemical and Aerosol Sounding Satellite) are calculated and contrasted. Retrieved THs have typical biases of 60m relative to those retrieved using the ACE version 3.x software after revisiting the temperature dependence of the N2 CIA (collision-induced absorption) laboratory measurements and accounting for sulfate aerosol extinction. After correcting for the known residual high bias of ACE version 3.x THs expected from CO2 spectroscopic/isotopic inconsistencies, the remaining bias for tangent heights determined with the N2 CIA is -20 m. CO2 in the 5-13 km range in the 2009-2011 time frame is validated against aircraft measurements from CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container), CONTRAIL (Comprehensive Observation Network for Trace gases by Airline), and HIPPO (HIAPER Pole-to-Pole Observations), yielding typical biases of -1.7 ppm in the 5-13 km range. The standard error of these biases in this vertical range is 0.4 ppm. The multiyear ACE-FTS data set is valuable in determining the seasonal variation of the latitudinal gradient which arises from the strong seasonal cycle in the Northern Hemisphere troposphere. The annual growth of CO2 in this time frame is determined to be 2.6 ± 0.4 ppm year-1, in agreement with the currently accepted global growth rate based on ground-based measurements. [ABSTRACT FROM AUTHOR]

This work describes the radiometric calibration of the short-wave infrared (SWIR) bands of two instruments aboard the Greenhouse gases Observing SATellite (GOSAT), the Thermal And Near infrared Sensor for carbon Observations Fourier Transform Spectrometer (TANSO-FTS) and the Cloud and Aerosol Imager (TANSO-CAI). Four vicarious calibration campaigns (VCCs) have been performed annually since June 2009 at Railroad Valley, NV, USA, to estimate changes in the radiometric response of both sensors. While the 2009 campaign ( VCC2009) indicated significant initial degradation in the sensors compared to the prelaunch values, the results presented here show that the stability of the sensors has improved with time. The largest changes were seen in the 0.76 μm oxygen A-band for TANSO-FTS and in the 0.380 and 0.674 μm bands for TANSO-CAI. This paper describes techniques used to optimize the vicarious calibration of the GOSAT SWIR sensors. We discuss error reductions, relative to previous work, achieved by using higher quality and more comprehensive in situ measurements and proper selection of reference remote sensing products from the Moderate Resolution Imaging Spectroradiometer used in radiative transfer calculations to model top-of-the-atmosphere radiances. In addition, we present new estimates of TANSO-FTS radiometric degradation factors derived by combining the new vicarious calibration results with the time-dependent model provided by Yoshida (2012), which is based on analysis of on-board solar diffuser data. We conclude that this combined model provides a robust correction for TANSO-FTS Level 1B spectra. A detailed error budget for TANSO-FTS vicarious calibration is also provided. [ABSTRACT FROM PUBLISHER]

Fourier transform spectrometry has played an important role in the three-dimensional greenhouse gas monitoring as the focus of attention on global warming in the past few years. In this paper, a ground-based low-resolution remote sensing system measuring the total columns of CO2 and CH4 is developed, which tracks the sun automatically and records the spectra in real-time and has the advantages of portability and low cost. A spectral inversion algorithm based on nonlinear least squares spectral fitting procedure for determining the column concentrations of these species is described. Atmospheric transmittance spectra are computed line-by-line in the forward model and observed on-line by direct solar radiation. Also, the wavelength shifts are introduced and the influence of spectral resolution is discussed. Based on this system and algorithm, the vertical columns of O2, CO2, and CH4 are calculated from total atmospheric observation transmittance spectra in Hefei, and the results show that the column averaged dry-air mole fractions of CO2 and CH4 are measured with accuracies of 3.7% and 5%, respectively. Finally, the H2O columns are compared with the results observed by solar radiometer at the same site and the calculated correlation coefficient is 0.92, which proves that this system is suitable for field campaigns and used to monitor the local greenhouse gas sources under the condition of higher accuracy, indirectly. [ABSTRACT FROM AUTHOR]

Abstract: Pressing open questions about the carbon cycle can be addressed with precise measurements of the three most abundant CO2 isotopologues 16O12C16O, 16O13C16O, and . Such measurements can, e.g., help to further constrain oceanic and biospheric net fluxes or to differentiate between the gross biospheric fluxes photosynthesis and respiration. The (about ) spectral region contains separated absorption lines of the three most abundant CO2 isotopologues. Their spectral properties make this spectral region well suited for the use of a light path proxy method for the retrieval of and (the ratio of heavier to lighter isotopologues relative to a standard). An optimal estimation based light path proxy retrieval for and has been set up, applicable to GOSAT (Greenhouse gases Observing Satellite) and ground-based FTS (Fourier transform spectrometer) measurements. Initial results show that it is possible to retrieve and from ground-based FTS instruments with a precision of and from GOSAT with a precision of about . Comparison of the achievable precision with the expected atmospheric signals shows that ground-based FTS remote sensing measurements have the potential to gain valuable information on and if averaging a sufficient number of measurements. It seems unlikely that this applies also to GOSAT because of the lower precision and a conceptual larger sensitivity to scattering related errors in satellite viewing geometry. [Copyright &y& Elsevier]

The article presents a study which focuses on comparison of aircraft measurements of carbon dioxide and methane in calibrating ground-based high-resolution Fourier Transform Spectrometers (g-b FTSs) with Greenhouse gases Observing Satellite (GOSAT). The study used airborne in situ and flask-sampling instruments which were mounted into the aircraft. The comparison shows that the impact of contributing factors, aerosol and thin cirrus cloud, on the retrieval from GOSAT were not negligible.

Abstract: The latest release of a high-resolution transmission molecular absorption database along with two improved models of water vapor continuum absorption are used to check their impact on the improvement of state-of-art radiative transfer. Radiative transfer performance has been assessed using high mountains atmospheric emitted spectral downwelling radiance observations in the 360–1200cm−1 spectral regions. These high mountains observations are particularly suited to check the behavior and performance in the water vapor rotation band. In addition, they also have allowed us to gain insight into understanding the quality of recent new compilation of lines and related treatment for the CO2 band and the O3 band at . Comparisons are made between forward calculations of atmospheric transmission spectra and spectral radiances measured using two ground-based Fourier transform instruments. The results demonstrate that water vapor absorption largely benefits from the recent improvement in the related continuum (both self and foreign). In addition, ozone absorption is very accurately reproduced and, although to a less extent, this is also the case of CO2 absorption in the long wave band. [Copyright &y& Elsevier]

Abstract: CO2 broadened spectra of the 1–0 band of H35Cl and H37Cl, observed near 2886cm−1, and the 1–0 band of D35Cl and D37Cl, located near 2089cm−1, have been recorded at room temperature and five total pressures between 150 and 700Torr, using a Bruker IFS125HR Fourier transform spectrometer. Spectra of pure HCl were also recorded. CO2 broadening and shift coefficients of HCl and DCl have been measured using multi-spectrum non-linear least squares fitting of Voigt profiles. The analysis of the 1–0 band of DCl was complicated by the presence of overlapping CO2 bands, which were included in the treatment as absorption coefficients calculated taking line-mixing effects into account. [Copyright &y& Elsevier]

The kinetic temperature and line of sight elevation information are retrieved from the MIPAS Middle Atmosphere (MA), Upper Atmosphere (UA) and NoctiLucent-Cloud (NLC) modes of high spectral resolution limb observations of the CO2 15 µm emission using the dedicated IMK/IAA retrieval algorithm, which considers non-local thermodynamic equilibrium conditions. These variables are accurately derived from about 20 km (MA) and 40 km (UA and NLC) to 105 km globally and both at daytime and nighttime. Typical temperature random errors are smaller than 0.5K below 50 km, 0.5-2K at 50-70 km, and 2-7K above. The systematic error is typically 1K below 70 km, 1-3K from 70 to 85 km and 3-11K from 85 to 100 km. The average vertical resolution is typically 4 km below 35 km, 3 km at 35-50 km, 4-6 km at 50-90 km, and 6-10 km above. We compared our MIPAS temperature retrievals from 2005 to 2009 with co-located ground-based measurements from the lidars located at the Table Mountain Facility and Mauna Loa Observatory, the SATI spectrograph in Granada (Spain) and the Davis station spectrometer, and satellite observations from ACE-FTS, Aura-MLS and TIMED-SABER from 20 km to 100 km. We also compared MIPAS temperatures with the high latitudes climatology from falling sphere measurements. The comparisons show very good agreement, with differences smaller than 3K below 85-90 km in midlatitudes. Differences over the poles in this altitude range are larger but can be generally explained in terms of known biases of the other instruments. The comparisons above 90 km worsen and MIPAS retrieved temperatures are always larger than other instrument measurements. [ABSTRACT FROM AUTHOR]

SCIAMACHY onboard ENVISAT (launched in 2002) enables the retrieval of global long-term column-averaged dry air mole fractions of the two most important anthropogenic greenhouse gases carbon dioxide and methane (denoted XCO2 and XCH4). In order to assess the quality of the greenhouse gas data obtained with the recently introduced v2 of the scientific retrieval algorithm WFM-DOAS, we present validations with ground-based Fourier Transform Spectrometer (FTS) measurements and comparisons with model results at eight Total Carbon Column Observing Network (TCCON) sites providing realistic error estimates of the satellite data. Such validation is a prerequisite to assess the suitability of data sets for their use in inverse modelling. It is shown that there are generally no significant differences between the carbon dioxide annual increases of SCIAMACHY and the assimilation system CarbonTracker (2.00± 0.16 ppm yr-1 compared to 1.94±0.03 ppm yr-1 on global average). The XCO2 seasonal cycle amplitudes derived from SCIAMACHY are typically larger than those from TCCON which are in turn larger than those from CarbonTracker. The absolute values of the northern hemispheric TCCON seasonal cycle amplitudes are closer to SCIAMACHY than to CarbonTracker and the corresponding differences are not significant when compared with SCIAMACHY, whereas they can be significant for a subset of the analysed TCCON sites when compared with CarbonTracker. At Darwin we find discrepancies of the seasonal cycle derived from SCIAMACHY compared to the other data sets which can probably be ascribed to occurrences of undetected thin clouds. Based on the comparison with the reference data, we conclude that the carbon dioxide data set can be characterised by a regional relative precision (mean standard deviation of the differences) of about 2.2 ppm and a relative accuracy (standard deviation of the mean differences) of 1.1-1.2 ppm for monthly average composites within a radius of 500 km. For methane, prior to November 2005, the regional relative precision amounts to 12 ppb and the relative accuracy is about 3 ppb for monthly composite averages within the same radius. The loss of some spectral detector pixels results in a degradation of performance thereafter in the spectral range currently used for the methane column retrieval. This leads to larger scatter and lower XCH4 values are retrieved in the tropics for the subsequent time period degrading the relative accuracy. As a result, the overall relative precision is estimated to be 17 ppb and the relative accuracy is in the range of about 10-20 ppb for monthly averages within a radius of 500 km. The derived estimates show that the SCIAMACHY XCH4 data set before November 2005 is suitable for regional source/sink determination and regional-scale flux uncertainty reduction via inverse modelling worldwide. In addition, the XCO2 monthly data potentially provide valuable information in continental regions, where there is sparse sampling by surface flask measurements. [ABSTRACT FROM AUTHOR]

The article presents a study which looks into the remote sensing of carbon dioxide (CO) and atmospheric methane (CH4) through solar absorption spectrometry. The study operates the high resolution instrument as part of the Total Carbon Column Observing Network (TCCON). It concludes that a low resolution Fourier Transform Spectrometry (FTS) instrument is effective in measuring XCO2.

Several existing and proposed satellite remote sensing instruments are designed to derive concentrations of trace gases, such as carbon dioxide (CO2) and methane (CH4), from measured spectra of reflected sunlight in absorption bands of the gases. Generally, these analyses require that the scenes be free of cloud and aerosol, necessitating robust screening algorithms. In this work, two cloud-screening algorithms are compared. One applies threshold tests, similar to those used by the MODerate resolution Imaging Spectrometer (MODIS), to visible and infrared reflectances measured by the Cloud and Aerosol Imager aboard the Greenhouse gases Observing SATellite (GOSAT). The second is a fast retrieval algorithm that operates on high-resolution spectra in the oxygen A-band measured by the Fourier Transform Spectrometer on GOSAT. Near-simultaneous cloud observations from the MODIS Aqua satellite are used for comparison. Results are expressed in terms of agreement and disagreement in the identification of clear and cloudy scenes for land and non-sun glint viewing over water. The accuracy, defined to be the fraction of scenes that are classified the same, is approximately 80% for both algorithms over land when comparing with MODIS. The accuracy rises to approximately 90% over ocean. Persistent difficulties with identifying cirrus clouds are shown to yield a large fraction of the disagreement with MODIS. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO 2) emitted from thermal power plants accounts for approximately 40% of energy-related CO 2 emissions in the world. CO 2 emission datasets for thermal power plants have large uncertainties, especially those from developing countries. We performed CO 2 column measurements with solar-viewing portable Fourier transform spectrometers and wind measurements with a Doppler lidar at sites approximately 3–7 km from a thermal power plant in Japan during field campaigns in October 2018 and October/November 2019 to evaluate the uncertainty in CO 2 emission estimates based on ground-based atmospheric measurements. Under the assumption that the CO 2 plume from a thermal power plant disperses according to a Gaussian plume model, CO 2 emission rates were estimated simultaneously with the dispersion coefficient of lateral plume width and wind direction by an optimal estimation method. The estimated CO 2 emission rates were in good agreement with those determined from hourly fuel consumption data, with a mean bias of 2.8% and a standard deviation of 16.8%. Analyses of 27 plumes observed for approximately one month during the 2019 campaign when the actual CO 2 emission rate was nearly constant revealed that monthly CO 2 emissions can be quantified with a precision (standard error) of 6.9% at the 95% confidence level. Evaluations using different wind data demonstrated that accurate data for determining the wind field are of importance in the column measurement-based emission estimates. • CO 2 column measurements were performed with portable FTSs around a power plant. • Wind data in the planetary boundary layer were observed with a Doppler lidar. • CO 2 emission rates were estimated by two (simple and optimal estimation) methods. • The emission rate uncertainty was evaluated by comparing with fuel consumption. • Precision of monthly emission estimate was equivalent to inventory uncertainties. [ABSTRACT FROM AUTHOR]

The Fourier Transform Spectrometer (FTS) at the Beijing Satellite Meteorological Ground Station observed XCO2 (the dry carbon dioxide column) from 2 March 2016 to 4 December 2018. The validation results of ground-based XCO2, as well as GOSAT, OCO-2, and TanSat XCO2, show that the best temporal matching setting for ground-based XCO2 and satellite XCO2 is ±1 h, and the best spatial matching setting for GOSAT is 0.5° × 0.5°. Consistent with OCO-2, the best spatial matching setting of TanSat is 5° × 5° or 6° × 6°. Among GOSAT, OCO-2, and TanSat, the satellite observation validation characteristics near 5° × 5° from the ground-based station are obviously different from other spatial matching grids, which may be due to the different observation characteristics of satellites near 5° × 5°. To study the influence of local CO2 sources on the characteristics of satellite observation validation, we classified the daily XCO2 observation sequence into concentrated, dispersive, increasing, and decreasing types, respectively, and then validated the satellite observations. The results showed that the concentrated and decreasing sub-datasets have better validation performance. Our results suggest that it is best to use concentrated and decreasing sub-datasets when using the Beijing Satellite Meteorological Ground Station XCO2 for satellite validation. The temporal matching setting should be ±1 h, and the spatial matching setting should consider the satellites observation characteristics of 5° × 5° distance from the ground-based station. [ABSTRACT FROM AUTHOR]

• Supercritical CO 2 technology was innovatively used on PVDF recycling. • PVDF dissolves completely using supercritical CO 2 - dimethyl sulfoxide system. • Recovered PVDF remained the same surficial chemical properties as the raw sample. • Supercritical CO 2 technology was effectively used in liberation of Li-ion battery cathode materials. The growing demand for energy storage devices due to the skyrocketing production/consumption of portable electrical and electronic equipment as well as electric vehicles has promoted battery technologies, resulting in the piling of a large number of waste lithium-ion batteries (LIBs). Organic binders wrapped on electrode particles are usually the main reason that causes the difficulty of liberation and extraction of electrode materials. Pyrolysis or incineration is the general approach to separate the organic binder, leading to fluorinated exhaust gas emissions. In this study, the supercritical carbon dioxide (SC CO 2) combined with a cosolvent dimethyl sulfoxide was innovatively adapted to enable the extraction of organic binders from spent LIBs to facilitate the liberation of the cathode material from aluminum foil. Pure polyvinylidene fluoride was preferentially used to study the SC CO 2 dissolution mechanism. The results indicate that 98.5 wt% polyvinylidene fluoride (PVDF) dissolves in SC CO 2 dimethyl sulfoxide system under the optimum conditions; 70°C process temperature, 80 bar pressure, and 13 min duration. After removing PVDF, the recovered sample was characterized by Fourier Transform Infrared Spectrometer (FTIR) and thermogravimetric analyzer (TGA) to observe its possible re-utilization. It is clear that the surficial chemical groups and content remained the same after treatment. SC CO 2 processing effectively liberates the active cathode material from the aluminum substrate due to removal of the binder. The suggested innovative approach is promising as an alternative pretreatment method due to its high efficiency, relatively low energy consumption, and environmentally friendly features. [Display omitted] [ABSTRACT FROM AUTHOR]

Single-atom MoN 2 site was introduced into COF to construct Mo-COF materials for photocatalytic conversion of CO 2 at atmosphere concentration to high added value hydrocarbons products (C x H y), such as CH 4 and C 2 H 4. [Display omitted] • COF with single-atom MoN 2 site was successfully prepared. • Single-atom MoN 2 site COF with showed excellent performance of photocatalytic reduction of CO 2. • The mechanism of single-atom MoN 2 site improving performance was revealed. The application of covalent organic framework (COF) for photocatalytic CO 2 conversion has received more and more attention. However, it is still a challenge for photocatalytic conversion of CO 2 with atmosphere concentration to high added value hydrocarbons products (C x H y) such as CH 4 and C 2 H 4. Here, integrating the advantages of micropore structure and single atom catalysis, we introduced single- atom MoN 2 sites into COF to construct Mo-COF materials. The aberration-COrrected high-angle annular dark-field scanning transmission electron microscopy (HAADF- STEM) confirms that Mo single atom on COF. Mo-COF can reduce CO 2 to C x H y under visible light with a selectivity of 42.92 % and C 2 H 4 product was found for the the first time. In-situ fourier transform infrared spectrometer (In situ FT-IR) and theoretical calculation showed that the introduction of single-atom MoN 2 sites is the key to improving the catalysis performance. It also provides a new idea for converting CO 2 into high added value C x H y products. [ABSTRACT FROM AUTHOR]

2• The Fourier transform (FT) spectra were employed to extend the study of hyperfine structure (HFS) in Co I and Co II. 2• HFS constants A for 36 levels of Co I from 0.00 to 60,262.463 cm−1 were determined, of which 33 results are reported for the first time, as far as we know. Our study increased the total number of HFS constants A to over 333 for Co I. 2• HFS constants A for 61 levels of Co II from 11,651.277 to 85,876.271 cm−1 were determined, of which 58 results are reported for the first time, as far as we know. Our study increased the total number of HFS constants A to over 86 for Co II. We used some archival data from the Fourier transform spectrometer (FTS) at the US National Solar Observatory to study the hyperfine structure (HFS) patterns of Co I and Co II, and determined the HFS constants of Co I and Co II. In total, HFS constants A for 36 levels of Co I from 0.00 to 60,262.463 cm−1 and for 61 levels of Co II from 11,651.277 to 85,876.271 cm−1 were determined, of which 33 results for Co I and 58 results for Co II are reported for the first time, as far as we know. Our study increased the total number of HFS constants A to over 333 for Co I and over 86 for Co II. [ABSTRACT FROM AUTHOR]

The Cross-track Infrared Sounder (CrIS) aboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite is a spaceborne Fourier transform infrared spectrometer. The study aims to retrieve carbon dioxide (CO2) information (the CO2 profile and column-averaged dry-air mole fraction of XCO2) from June 2018 to December 2019 based on the The National Oceanic and Atmospheric Administration (NOAA)-Unique Combined Atmospheric Processing System (NUCAPS) Cloud-Cleared Radiances (CCRs) via the CrIS. The CCRs products for the CrIS with 2223 channels have been available since 22 May 2018. Characteristics of the CO2 weighting functions inform the choice of multiple channels that are around 15 μm in size that differ by latitude and season to maximize retrieval sensitivity to CO2 and minimize sensitivity to other interfering atmospheric parameters. CO2 was retrieved from these channels using an adopted nonlinear optimization algorithm. The temperature, water vapor, and ozone profiles used in the inversion process were gathered from the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5). Validations of CO2 concentrations as retrieved from CrIS showed the following conclusions: (1) The relative error of the retrieved CO2 concentrations, as compared to Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container (CARIBIC) in situ aircraft measurements, was less than 0.5%, and the root mean square errors (RMSE) were less than 0.7 ppmv (with correlation coefficients of 0.56–0.86); (2) the retrieved XCO2 from June 2018 to December 2019 correlated well with the ground-based Total Carbon Column Observing Network (TCCON) observations, and the differences were within ±0.2 ppmv. Further analysis of the temporal and spatial distribution of the retrieved CO2 at 300 hPa demonstrated a strong seasonal variation of CO2 in 0–60° N in the Northern Hemisphere with the maximum values in June–August and larger amplitudes of seasonal variation in the northeast of Asia and northeastern part of North America. The variations likely occurred due to larger sinks of atmospheric CO2 that are dominated by CO2 uptake in the summer. In the Southern Hemisphere, the CO2 displayed high concentration anomalies in the latitudinal range of 30–60° S in September–November and December–February, which probably occurred due to the lofted smoke plumes from the strong fire seasons in South America and Southern Africa. [ABSTRACT FROM AUTHOR]

• Catalytic ethanolysis of Xilinguole lignite with MMgAlO x was conducted. • The MMgAlO x have layered and mesoporous structures with tunable acidity/basicity. • Yields of ethanol-soluble portions can be dramatically enhanced by the catalysts. • The catalysts can preferably reserve the aromatic rings to produce arenes and phenols. • Platform chemicals can be controlled by changing the catalysts. Ethanolysis is an efficient approach for converting lignites into chemicals under mild conditions. However, yield of soluble portion from lignite ethanolysis is limited and product distribution cannot be well regulated. In this paper, a series of catalysts (MMgAlO x , M = Cu, Zn, Co, Ni) were prepared by a coprecipitation method. The catalysts were characterized by X-ray powder diffraction, high resolution transmission electron microscope, N 2 physisorption, and CO 2 - and NH 3 -temperature-programed desorption. The results show that the catalysts have layered and mesoporous structures with tunable acidity/basicity. Catalytic ethanolysis of Xilinguole lignite was performed and the resulting ethanol-soluble portions (ESPs) were analyzed with a Fourier transform infrared spectrometer, thermogravimetric analyzer, and gas chromatograph/mass spectrometer. The results suggest that except NiMgAlO x , other catalysts significantly increased the yields of the ESPs, especially CuMgAlO x and ZnMgAlO x , which is probably related to the amount of H 2 produced from ethanol. Four major platform chemicals, i.e., arenes, phenols, alcohols, and esters, can be produced via the catalytic ethanolysis. The catalysts have high ethanolysis activity and low hydrogenation ability and therefore aromatic rings can be reserved. Distribution of the platform chemicals could be tuned by altering the catalysts. In addition, possible pathways on the catalytic ethanolysis were proposed. [ABSTRACT FROM AUTHOR]

• Laboratory measured line intensities of the 01111–00001 magnetic dipole band of 12C16O 2. • Measured line intensities of the 01111–00001 electric dipole band of 16O12C18O. • Refined value of the vibrational transition magnetic dipole moment for the 01111–00001 band of 12C16O 2. The spectra of carbon dioxide in the 3.3 µm region were recorded at three pressures using Bruker IFS 125 HR Fourier transform spectrometer and a 30 m base multipass gas cell of V.E. Zuev Institute of Atmospheric Optics SB RAS. Several lines of the 01111–00001 (ν 2 + ν 3) magnetic dipole band of 12C16O 2 were detected and their line intensities were measured. The vibrational transition magnetic dipole moment was fitted to the observed line intensities. The fitted value of the vibrational transition magnetic dipole moment of 0.71(1) µ N is substantially smaller than the value of 0.96µ N obtained in the result of the analysis of the Martian atmosphere spectra (here µ N is the nuclear magneton). Using the known set of the effective Hamiltonian parameters and fitted value of the vibrational transition magnetic dipole moment the list of the line parameters of this band was generated for the HITRAN database. In addition the line intensities of the R-branch of the electric dipole 01111–00001 band of the 16O12C18O isotopologue were measured for the first time. [ABSTRACT FROM AUTHOR]