Search

We developed and tested a complete measurement system to quantify CO2 and CH4 emissions at the scale of an industrial site based on the innovative sensor Airborne Ultra-light Spectrometer for Environmental Application (AUSEA), operated on board uncrewed aircraft vehicles (UAVs). The AUSEA sensor is a new light-weight (1.4 kg) open-path laser absorption spectrometer simultaneously recording in situ CO2 and CH4 concentrations at high frequency (24 Hz in this study) with precisions of 10 ppb for CH4 and 1 ppm for CO2 (when averaged at 1 Hz). It is suitable for industrial operation at a short distance from the sources (sensitivity up to 1000 ppm for CO2 and 200 ppm for CH4). Greenhouse gas concentrations monitored by this sensor throughout a plume cross section downwind of a source drive a simple mass balance model to quantify emissions from this source. This study presents applications of this method to different pragmatic cases representative of real-world conditions for oil and gas facilities. Two offshore oil and gas platforms were monitored for which our emissions estimates were coherent with mass balance and combustion calculations from the platforms. Our method has also been compared to various measurement systems (gas lidar, multispectral camera, infrared camera including concentrations and emissions quantification system, acoustic sensors, ground mobile and fixed cavity ring-down spectrometers) during controlled-release experiments conducted on the TotalEnergies Anomaly Detection Initiatives (TADI) test platform at Lacq, France. It proved suitable to detect leaks with emission fluxes down to 0.01 gs-1 , with 24 % of estimated CH4 fluxes within the - 20 % to + 20 % error range, 80 % of quantifications within the - 50 % to + 100 % error range and all of our results within the - 69 % to + 150 % error range. Such precision levels are better ranked than current top-down alternative techniques to quantify CH4 at comparable spatial scales. This method has the potential to be operationally deployed on numerous sites and on a regular basis to evaluate the space- and time-dependent greenhouse gas emissions of oil and gas facilities. [ABSTRACT FROM AUTHOR]

Fire is considered as an essential climate variable, emitting greenhouse gases in the combustion process. Current global assessments of fire emissions traditionally rely on coarse remotely-sensed burned area data, along with biome-specific combustion completeness and emission factors, to provide near real-time information. However, large uncertainties persist regarding burned areas, biomass affected, and emission factors. Recent increases in resolution have improved previous estimates of burned areas and aboveground biomass, while increasing the information content used to derive emission factors, complemented by airborne sensors deployed in the Tropics. To date, temperate forests, characterized by a lower fire incidence and stricter aerial surveillance restrictions near wildfires, have received less attention. In this study, we leveraged the distinctive fire season of 2022, which impacted Western European temperate forests, to investigate fire emissions monitored by the atmospheric tower network. We examined the role of soil smoldering combustion responsible for higher carbon emissions, locally reported by firefighters but not accounted for in global fire emission budgets. We assessed the CO/CO2 ratio released by major fires in the Mediterranean, Atlantic pine, and Atlantic temperate forests of France. Our findings revealed low Modified Combustion Efficiency (MCE) for the two Atlantic temperate regions, supporting the assumption of heavy smoldering combustion. This type of combustion was associated with specific fire characteristics, such as long-lasting thermal fire signals, and affected ecosystems encompassing needle leaf species, peatlands, and superficial lignite deposits in the soils. Thanks to high-resolution data (approximately 10 meters) on burned areas, tree biomass, peatlands, and soil organic matter, we proposed a revised combustion emission framework consistent with the observed MCEs. Our estimates revealed that 6.15 MtCO2 (± 2.65) were emitted, with belowground stock accounting for 51.75% (± 16.05). Additionally, we calculated a total emission of 1.14 MtCO (± 0.61), with 84.85% (± 3.75) originating from belowground combustion. As a result, the carbon emissions from the 2022 fires in France amounted to 7.95 MteqCO2 (± 3.62). These values exceed by 2-fold the generic GFAS global estimates of 4.18 MteqCO2 (CO and CO2). Fires represent 1.97% (± 0.89) of the country's annual carbon footprint, corresponding to a reduction of 30 % of the forest carbon sink this year. Consequently, we conclude that current European fire emissions estimates should be revised to account for soil combustion in temperate forests. We also recommend the use of atmospheric mixing ratios as an effective monitoring system of prolonged soil fires that have the potential to reignite in the following weeks. [ABSTRACT FROM AUTHOR]

Fire is considered as an essential climate variable, emitting greenhouse gases in the combustion process. Current global assessments of fire emissions traditionally rely on coarse remotely-sensed burned area data, along with biome-specific combustion completeness and emission factors, to provide near real-time information. However, large uncertainties persist regarding burned areas, biomass affected, and emission factors. Recent increases in resolution have improved previous estimates of burned areas and aboveground biomass, while increasing the information content used to derive emission factors, complemented by airborne sensors deployed in the Tropics. To date, temperate forests, characterized by a lower fire incidence and stricter aerial surveillance restrictions near wildfires, have received less attention. In this study, we leveraged the distinctive fire season of 2022, which impacted Western European temperate forests, to investigate fire emissions monitored by the atmospheric tower network. We examined the role of soil smoldering combustion responsible for higher carbon emissions, locally reported by firefighters but not accounted for in global fire emission budgets. We assessed the CO/CO2 ratio released by major fires in the Mediterranean, Atlantic pine, and Atlantic temperate forests of France. Our findings revealed low Modified Combustion Efficiency (MCE) for the two Atlantic temperate regions, supporting the assumption of heavy smoldering combustion. This type of combustion was associated with specific fire characteristics, such as long-lasting thermal fire signals, and affected ecosystems encompassing needle leaf species, peatlands, and superficial lignite deposits in the soils. Thanks to high-resolution data (approximately 10 meters) on burned areas, tree biomass, peatlands, and soil organic matter, we proposed a revised combustion emission framework consistent with the observed MCEs. Our estimates revealed that 6.15 MtCO2 (± 2.65) were emitted, with belowground stock accounting for 51.75% (± 16.05). Additionally, we calculated a total emission of 1.14 MtCO (± 0.61), with 84.85% (± 3.75) originating from belowground combustion. As a result, the carbon emissions from the 2022 fires in France amounted to 7.95 MteqCO2 (± 3.62). These values exceed by 2-fold the generic GFAS global estimates of 4.18 MteqCO2 (CO and CO2). Fires represent 1.97% (± 0.89) of the country's annual carbon footprint, corresponding to a reduction of 30 % of the forest carbon sink this year. Consequently, we conclude that current European fire emissions estimates should be revised to account for soil combustion in temperate forests. We also recommend the use of atmospheric mixing ratios as an effective monitoring system of prolonged soil fires that have the potential to reignite in the following weeks. [ABSTRACT FROM AUTHOR]

We developed an innovative tool to quantify CO2 and CH4 emissions at the scale of an industrial site, based on a mass balance approach relying on a newly developed light-weight (1.4 kg) open path laser absorption spectrometer operable on-board Unmanned Aircraft Vehicles (UAVs). This spectrometer simultaneously records in situ CO2 and CH4 concentrations at high frequency (24 Hz in this study) with precisions of 10 ppb for CH4 and 1 ppm for CO2 averaged at 1 Hz. The large range of measurable concentrations, up to 1000 ppm for CO2 and 200 ppm for CH4, makes this analyzer suitable for operation on industrial sites at a short distance from the emission sources, therefore avoiding many logistical and legal limits associated with most long-range airborne observations. To quantify the emissions, high spatial resolution atmospheric concentration measurements obtained throughout a plume cross-section downwind of a source within the limited UAV flight period are exploited by calculations using a mass balance approach. This high spatial resolution, allowed by the high acquisition frequency, limits the use of horizontal interpolation, thus gaining in precision compared to current airborne alternative quantification techniques. A field validation campaign, conducted on the TotalEnergies TADI test platform at Lacq, France, consisted in controlled CO2 and CH4 leak experiments to which several institutes participated with various measurement systems (gas LiDAR, multispectral camera, infrared camera including concentrations and emissions quantification system, acoustic sensors, ground mobile and fixed Cavity RingDown Spectrometers). Our method was proved suitable to detect leaks during controlled release experiments with emission fluxes down to 0.01 g s-1, with 24 % of estimated CH4 fluxes within the -20 % to +20 % error range, 80 % of quantifications within the 50 % to +100 % error range and all of our results within the -69 % to +150 % error range. Such precision levels are better ranked than current top-down alternative techniques to quantify CH4 at comparable spatial scales. Observations across the plume of two offshore oil and gas platforms operated by TotalEnergies in the North Sea were used to quantify the instantaneous greenhouse gases emissions of these facilities and are coherent with reference emissions for these platforms estimated by mass balance and combustion calculations for CO2. The operational deployment of such instruments and quantification methods, on a large scale and on a regular basis, potentially with fully autonomous UAVs, will allow the quantification of the time dependent greenhouse gases emissions of numerous oil and gas facilities. [ABSTRACT FROM AUTHOR]

We report in this paper the development of an embedded ultralight spectrometer (<3 kg) based on tuneable diode laser absorption spectroscopy (with a sampling rate of 24 Hz) in the mid-infrared spectral region. This instrument is dedicated to in situ measurements of the vertical profile concentrations of three main greenhouse gases – carbon dioxide (CO2), methane (CH4) and water vapour (H2O) – via standard weather and tethered balloons. The plug and play instrument is compact, robust, cost-effective, and autonomous. The instrument also has low power consumption and is non-intrusive. It was first calibrated during an in situ experiment on an ICOS (Integrated Carbon Observation System) site for several days, then used in two experiments with several balloon flights of up to 30 km altitude in the Reims region of France in 2017–2018 in collaboration with Météo-France CNRM (Centre National de Recherches Météorologiques). This paper shows the valuable interest of the data measured by the AMULSE (Atmospheric Measurements by Ultra-Light Spectrometer) instrument during the APOGEE (Atmospheric Profiles of Greenhouse Gases) measurement experiment, specifically for the vertical profiles of CO2 and CH4 , measurements of which remain very sparse. We have carried out several experiments showing that the measured profiles have several applications: the validation of simulations of infrared satellite observations, evaluating the quality of chemical profiles from chemistry transport models (CTMs) and evaluating the quality of retrieved chemical profiles from the assimilation of infrared satellite observations. The results show that the simulations of infrared satellite observations from IASI (Infrared Atmospheric Sounding Interferometer) and CrIS (Cross-track Infrared Sounder) instruments performed in operational mode for numerical weather prediction (NWP) by the radiative transfer model (RTM) RTTOV (Radiative Transfer for the TIROS Operational Vertical Sounder) are of good quality. We also show that the MOCAGE (Modèle de Chimie Atmosphérique de Grande Echelle) and CAMS (Copernicus Atmospheric Monitoring Service) CTMs modelled ozone profiles fairly accurately and that the CAMS CTM represents the methane in the troposphere well compared to MOCAGE. Finally, the measured in situ ozone profiles allowed us to show the good quality of the retrieved ozone profiles by assimilating ozone-sensitive infrared spectral radiances from the IASI and CrIS. [ABSTRACT FROM AUTHOR]

The Integrated Carbon Observation System Research Infrastructure aims to provide long-term, continuous observations of sources and sinks of greenhouse gases such as carbon dioxide, methane, nitrous oxide, and water vapour. At ICOS ecosystem stations, the principal technique for measurements of ecosystem-atmosphere exchange of GHGs is the eddy-covariance technique. The establishment and setup of an eddy-covariance tower have to be carefully reasoned to ensure high quality flux measurements being representative of the investigated ecosystem and comparable to measurements at other stations. To fulfill the requirements needed for flux determination with the eddycovariance technique, variations in GHG concentrations have to be measured at high frequency, simultaneously with the wind velocity, in order to fully capture turbulent fluctuations. This requires the use of high-frequency gas analysers and ultrasonic anemometers. In addition, to analyse flux data with respect to environmental conditions but also to enable corrections in the post-processing procedures, it is necessary to measure additional abiotic variables in close vicinity to the flux measurements. Here we describe the standards the ICOS ecosystem station network has adopted for GHG flux measurements with respect to the setup of instrumentation on towers to maximize measurement precision and accuracy while allowing for flexibility in order to observe specific ecosystem features. [ABSTRACT FROM AUTHOR]

The Integrated Carbon Observation System Research Infrastructure aims to provide long-term, continuous observations of sources and sinks of greenhouse gases such as carbon dioxide, methane, nitrous oxide, and water vapour. At ICOS ecosystem stations, the principal technique for measurements of ecosystem-atmosphere exchange of GHGs is the eddy-covariance technique. The establishment and setup of an eddy-covariance tower have to be carefully reasoned to ensure high quality flux measurements being representative of the investigated ecosystem and comparable to measurements at other stations. To fulfill the requirements needed for flux determination with the eddycovariance technique, variations in GHG concentrations have to be measured at high frequency, simultaneously with the wind velocity, in order to fully capture turbulent fluctuations. This requires the use of high-frequency gas analysers and ultrasonic anemometers. In addition, to analyse flux data with respect to environmental conditions but also to enable corrections in the post-processing procedures, it is necessary to measure additional abiotic variables in close vicinity to the flux measurements. Here we describe the standards the ICOS ecosystem station network has adopted for GHG flux measurements with respect to the setup of instrumentation on towers to maximize measurement precision and accuracy while allowing for flexibility in order to observe specific ecosystem features. [ABSTRACT FROM AUTHOR]

Methane plays an important role in the radiative balance of the Earth climate: about 20% of the manmade global warming is related to methane emissions. To contribute to the study of CH trends, we have developed a compact lightweight spectrometer (2.5 kg) by combining an antimonide laser diode at 3.24 µm with an 8 m optical multipass path cell open to the atmosphere. This laser sensor is to be operated from weather balloons to provide with regular in situ methane soundings from ground level up to ~ 25 km. In this paper, the laser sensor is described as well as the processing of the absorption spectra and the calibration of the instrument. The concentration data obtained from recent stratospheric balloon flights are reported and discussed. [ABSTRACT FROM AUTHOR]

The concentration of greenhouse gases in the atmosphere plays an important role in the radiative effects in the Earth's climate system. Therefore, it is crucial to increase the number of atmospheric observations in order to quantify the natural sinks and emission sources. We report in this paper the development of a new compact lightweight spectrometer (1.8 kg) called AMULSE based on near infrared laser technology at 2.04 μm coupled to a 6-m open-path multipass cell. The measurements were made using the Wavelength Modulation Spectroscopy (WMS) technique and the spectrometer is hence dedicated to in situ measuring the vertical profiles of the CO2 at high precision levels (σAllan = 0.96 ppm in 1 s integration time (1σ) and with high temporal/spatial resolution (1 Hz/5 m) using meteorological balloons. The instrument is compact, robust, cost-effective, fully autonomous, has low-power consumption, a non-intrusive probe and is plug & play. It was first calibrated and validated in the laboratory and then used for 17 successful flights up to 10 km altitude in the region Champagne--Ardenne, France in 2014. A rate of 100% of instrument recovery was validated due to the pre-localization prediction of the Météo--France based on the flight simulation software. [ABSTRACT FROM AUTHOR]

Both laboratory and field experiments were carried out in order to define suitable configuration ranges for the gas sampling systems (GSSs) of infrared gas analyzers (IRGAs) used in eddy covariance measurements. In the laboratory, an original dynamic calibration bench was developed in order to test the frequency attenuation and pressure drop generated by filters. In the field, three IRGAs of the same type equipped with different filters or different rain caps were installed and run and the real frequency response of the complete setup was tested. The main results are as follows. * Filters may have a strong impact on the pressure drop in the GSS and this impact increases with flow rate. * Conversely, no impact of the tested filters on cut-off frequency was found, GSSs with and without filters pre senting similar cut-off frequencies. * The main limiting factor of cut-off frequency in the field was found to be the rain cap design. In addition, the impact of this design on pressure drop was also found to be noteworthy. [ABSTRACT FROM AUTHOR]

Both laboratory and field experiments were carried out in order to define suitable configuration ranges for the gas sampling systems (GSSs) of infrared gas analyzers (IRGAs) used in eddy covariance measurements. In the laboratory, an original dynamic calibration bench was developed in order to test the frequency attenuation and pressure drop generated by filters. In the field, three IRGAs of the same type equipped with different filters or different rain caps were installed and run and the real frequency response of the complete setup was tested. The main results are as follows. - Filters may have a strong impact on the pressure drop in the GSS and this impact increases with flow rate. - Conversely, no impact of the tested filters on cut-off frequency was found, GSSs with and without filters presenting similar cut-off frequencies. - The main limiting factor of cut-off frequency in the field was found to be the rain cap design. In addition, the impact of this design on pressure drop was also found to be noteworthy. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the interest of the singular value decomposition (SVD) data processing method applied to the in situ monitoring of gases (NO) b mid-infrared quantum cascade laser absorption spectroscopy. An approach by simulation is used to determine the most appropriate parameters of the SVD treatment for this specific laser sensing application. The simulation is further used to estimate the effectiveness of the SVD in terms of improvement of the concentration data precision. Finally, the proposed SVD method is applied to experimental NO measurements achieved in the laboratory with calibrated gas samples and with NO flux measurements yielded during a field campaign in farm parcels. [ABSTRACT FROM AUTHOR]

The main characteristics that a sensor must possess for trace gas detection and pollution monitoring are high sensitivity, high selectivity and the capability to perform in situ measurements. The photacoustic Helmholtz sensor developed in Reims, used in conjunction with powerful Quantum Cascade Lasers (QCLs), fulfils all these requirements. The best cell response is # 1200 V W−1 cm and the corresponding ultimate sensitivity is j 3.3 × 10−10 W cm−11 Hz−11/2. This efficient sensor is used with mid-infrared QCLs from Alpes Lasers to reach the strong fundamental absorption bands of some atmospheric gases. A first cryogenic QCL emitting at 7.9 μm demonstrates the detection of methane in air with a detection limit of 3 ppb. A detection limit of 20 ppb of NO in air is demonstrated using another cryogenic QCL emitting in the 5.4 μm region. Real in-situ measurements can be achieved only with room-temperature QCLs. A room-temperature QCL emitting in the 7.9 μm region demonstrates the simultaneous detection of methane and nitrous oxide in air (17 and 7 ppb detection limit, respectively). All these reliable measurements allow the estimated detection limit for various atmospheric gases using quantum cascade lasers to be obtained. Each gas absorbing in the infrared may be detected at a detection limit in the ppb or low-ppb range. [ABSTRACT FROM AUTHOR]

A network of remote and in-situ sensors was deployed in a Paris suburb in order to evaluate the mesoscale evolution of the daily cycle of CO2 and related tracers in the atmospheric boundary layer (ABL) and its relation to ABL dynamics and nearby natural and anthropogenic sources and sinks. A 2-μm heterodyne Doppler differential absorption lidar, which combines measurements of, (1) structure of the atmosphere, (2) radial velocity, and (3) CO2 differential absorption was a particularly unique element of the observational array. We analyse the differences in the diurnal cycle of CO, CO2, lidar reflectivity (a proxy for aerosol content) and H2O using the lidar, airborne measurements in the free troposphere and ground-based measurements made at two sites located few kilometres apart. We demonstrate that vertical mixing dominates the early morning drawdown of CO and aerosol content trapped in the former nocturnal layer but not the H2O and CO2 mixing ratio variations. Surface fluxes, vertical mixing and advection all contribute to the ABL CO2 mixing ratio decrease during the morning transition, with the relative importance depending on the rate and timing of ABL rise. We also show evidence that when the ABL is stable, small-scale (0.1-km vertical and 1-km horizontal) gradients of CO2 and CO are large. The results illustrate the complexity of inferring surface fluxes of CO2 from atmospheric budgets in the stable boundary layer. [ABSTRACT FROM AUTHOR]