Abstract Remote sensing technologies are some of the most powerful tools for atmospheric monitori... more Abstract Remote sensing technologies are some of the most powerful tools for atmospheric monitoring of natural or anthropogenic ecosystems. Extensive developments were observed in the two last decades concerning both satellite, airborne, on-board and ground systems. The present paper focuses on an advanced 3D reconstruction of a gas cloud detected in the atmosphere of an urban area using a scanning infrared (IR) gas system (SIGIS2, Bruker). Several measurements were carried out from 3 different positions in order to monitor an atmospheric volume around 108 m3. The images generated by the imaging remote sensing system correspond to the 2-D projections of the 3-D gas cloud. All the 2-D data are fully georeferenced (x, y, z and t). Each pixel of the 2-D images is associated to an IR spectrum, which was approximated to a linear combination of reference spectra and expressed as a coefficient of correlation (0 to 1). Data with a correlation coefficient higher than 0.75 are selected for 3-D modeling. The method for 3-D reconstruction of gas clouds is based on the combination and relocation of all the oriented and georeferenced measurement data. The 3-D gas cloud is determined from the 2-D images in the volume of interest processing a 3-D interpolation using the gOcad® DSI procedure. This integrated approach was applied to a local case study in an urban area. It leads to the identification and the spatial demarcation of a cloud of SO2 with a total volume of 65 × 106 m3. The existence of this pollutant may be related to the presence of ancient underground tanks of gasoline, leaking because of a defect of waterproofness. Another source of SO2 can be the emission of gases stemming from diesel machines used for important public works in this urban area. This study demonstrates that the combination of scanning imaging IR spectroscopy with the measurement setup and the 3-D gOcad® processing can be used as a generic approach for 3-D reconstruction of gas clouds applied to any kind of ground emissive sites.
Volcanic CO2 emissions inventories have great importance in the understanding of the geological c... more Volcanic CO2 emissions inventories have great importance in the understanding of the geological carbon cycle. Volcanoes provide the primary pathway for solid-earth volatiles to reach the Earth’s atmosphere and have the potential to significantly contribute to the carbon-climate feedback. Volcanic carbon emissions (both passive and eruptive degassing) included in inventories, largely stem from patchy surface measurements that suffer from difficulties in removing the atmospheric background. With a 27-year-long ongoing open-vent eruption, Popocatépetl ranks as one of the highest permanent volcanic CO2 emitters worldwide and provides an excellent natural laboratory to design and experiment with new remote sensing methods for volcanic gas emission measurements. Since October 2012, infrared spectra at different spectral regions have been recorded with a solar occultation FTIR spectrometer. The near-infrared spectra allow for high precision measurements of CO2 and HCl columns. Under favora...
Volcanic plume composition is strongly influenced by both changes in magmatic systems and plume-a... more Volcanic plume composition is strongly influenced by both changes in magmatic systems and plume-atmosphere interactions. Understanding the degassing mechanisms controlling the type of volcanic activity implies deciphering the contributions of magmatic gases reaching the surface and their posterior chemical transformations in contact with the atmosphere. Remote sensing techniques based on direct solar absorption spectroscopy provide valuable information about most of the emitted magmatic gases but also on gas species formed and converted within the plumes. In this study, we explore the procedures, performances and benefits of combining two direct solar absorption techniques, high resolution Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet Differential Optical Absorption Spectroscopy (UV-DOAS), to observe the composition changes in the Popocatépetl’s plume with high temporal resolution. The SO2 vertical columns obtained from three instruments (DOAS, high resolution FTIR ...
Total column H2O is measured by two remote sensing techniques at the Altzomoni Atmospheric Observ... more Total column H2O is measured by two remote sensing techniques at the Altzomoni Atmospheric Observatory (19° 12'N, 98° 65'W, 4000 m a.s.l.), a high-altitude, tropical background site in central Mexico. A ground-based solar absorption FTIR spectrometer that is part of the Network for Detection of Atmospheric Composition Change (NDACC) is used to retrieve water vapor in three spectral regions (6074-6471, 2925-2941 and 1110-1253 cm-1) and is compared to data obtained from a GPS (Global Positioning System) receiver that is part of the TLALOCNet GPS-meteorological network. Strong correlations are obtained between the coincident hourly means from the three FTIR products and small relative bias and correction factors could be determined for each when compared to the more consistent GPS data. Retrievals from the 2925-2941 cm-1 spectral region have the highest correlation with GPS (R2= 0.998, std= 0.18 cm (78.39%), mean diff= 0.04 cm (8.33%)), although the other products are also high...
<p>About seventy-five percent of the global carbon dioxide emissions from fossil fuel come ... more <p>About seventy-five percent of the global carbon dioxide emissions from fossil fuel come from cities. Reducing anthropogenic greenhouse gas emissions, in particular in developing countries, is a major concern for local, national and international policies. Different mitigation strategies are and will be implemented to reduce greenhouse gas emissions, and the evaluation of their success and their perennization depends on the ability to continuously measure and quantify the effects at different spatial and temporal scales.</p><p>Using continuous solar absorption Fourier transform Spectroscopy (FTIR) column measurements in both urban and background environments over the Mexico City metropolitan area, together with in situ datasets, we explore the spatial and temporal variability of the CO2 concentration over the 5 last years in the region. Measurements were performed from three permanent stations equipped with high and low spectral resolution FTIR spectrometers since 2012, 2016 and 2018, respectively, the first is part of the NDACC network while the other two contribute to the COCCON international initiative.</p><p>In the frame of the Mexico City&#8217;s Regional Carbon Impacts (MERCI-CO2) project, 4 complementary sites equipped with EM27/Sun instruments were temporarily implemented within the megacity since autumn 2020. In particular, our time series encompass the COVID shutdown in MCMA. In this contribution we present results of the long term measurements in background and urban environment, intercomparison measurements, and preliminary results of the temporary MERCI-CO2 stations. In addition we report about the obstacles and opportunities of this intensive measurement campaign.</p>
<p><span>Knowledge about water vapor isotopologues is a useful tool in the study of t... more <p><span>Knowledge about water vapor isotopologues is a useful tool in the study of the hydrological cycle. Total columns of water vapor isotopologues (H</span><sub><span>2</span></sub><sup><span>16</span></sup><span>O, H</span><sub><span>2</span></sub><sup><span>18</span></sup><span>O and HD</span><sup><span>16</span></sup><span>O) are measured by ground-based solar absorption FTIR spectroscopy at Altzomoni (3985 m.a.s.l, 19.12&#186;N, 98.66&#186;W), a high altitude subtropical remote background site in central Mexico (Barthlott et al., 2017). In the contribution we present the time series of the isotopic composition of water vapor columns and profiles above central Mexico and analyze differences in the isotopic ratios of H</span><sub><span>2</span></sub><sup><span>16</span></sup><span>O, H</span><sub><span>2</span></sub><sup><span>18</span></sup><span>O and HD</span><sup><span>16</span></sup><span>O between the rain and dry seasons of the year: in the rain season, changes in the isotopic ratios might be dominated by the diurnal cycle, which correlates with the relative humidity, temperature and dew point, while isotopic ratio in the dry season might depend more on the origin of the air parcels and transportation. We discuss the hydrological cycle in central Mexico using the relationship between light and heavy isotopes, and how this relationship gives valuable information about the pathways, sources and transport.</span></p>
<p>The Mexico City Metropolitan Area (MCMA), located in proximity to an active volcano, is ... more <p>The Mexico City Metropolitan Area (MCMA), located in proximity to an active volcano, is the largest urban center in North America and there is great interest to better characterize carbon emissions of this and other major urban centers in the country. NASA&#8217;s Orbiting Carbon Observatory (OCO-3) was installed in the International Space (ISS) in 2019. The inclusion of a Pointing Mirror Assembly (PMA) in this third iteration allows for a new mode of data collection that samples an area of ~80 x 80 km in approximately 2 minutes. This mode is used to collect map-like data, called Snapshot Area Maps (SAMs), over areas of interest (e.g. volcanos or urban areas). The OCO-3 module has collected SAMs over the MCMA (and the Popocat&#233;petl volcano) throughout 2020, and also of the metropolitan areas of Guadalajara and Monterrey throughout the second half of 2020.</p><p>Using data from the public release of OCO-3 Level 2 (L2) &#8220;Lite EarlyR&#8221; product, available at the Goddard Earth Sciences Data and Information Services Center (GES DISC), we have built maps of the spatial distribution of xCO<sub>2</sub> for these regions. Data is filtered according to the reported quality flag in the data product, compared with ground-based FTIR measurements of column xCO<sub>2</sub> over the MCMA region and averaged with an oversampling method. Surface pressure data with the averaged xCO<sub>2</sub> is used to calculate the concentrations within the mixed layer (xCO<sub>2</sub><sup>ML</sup>) in order to compensate for the effects of the complex terrain.&#160; This product is also used&#160; for comparison with CO spatial distributions obtained from TROPOMI data products and a simple xCO<sup>ML</sup>/xCO<sub>2</sub><sup>ML</sup> ratio is obtained and mapped for the three urban centers. This work showcases the utility of SAMs in cooperation with ground-based measurements to produce detailed descriptions of the spatial distribution of CO<sub>2</sub> for a wide variety of applications, as well as the importance of frequent soundings over important emission sources around the world.</p>
Urban areas are important contributors to the increase of global CO2 levels due to human activiti... more Urban areas are important contributors to the increase of global CO2 levels due to human activities, but continuous records of CO2 concentration in cities are scarce, especially in the developing world. In this study we present five years of simultaneous, in-situ measurements at a university campus in the south of Mexico City (UNAM) and at a high-altitude station, the Altzomoni atmospheric observatory (ALTZ), 60 km apart from the first site. The characteristics of the daily cycles, seasonality, and long-term trends were extracted from both time series. The features of the daily and seasonal cycles at UNAM are dominated by the dynamics of the boundary layer growth, while the seasonality at Altzomoni is determined by both the local meteorology and the photosynthetic activity of the vegetation. Annual CO2 growth rates of 2.4 and 2.6 ppm yr–1 were estimated for UNAM and Altzomoni, respectively, in close agreement with reported global growth rates and with previous estimates of total col...
Abstract Remote sensing technologies are some of the most powerful tools for atmospheric monitori... more Abstract Remote sensing technologies are some of the most powerful tools for atmospheric monitoring of natural or anthropogenic ecosystems. Extensive developments were observed in the two last decades concerning both satellite, airborne, on-board and ground systems. The present paper focuses on an advanced 3D reconstruction of a gas cloud detected in the atmosphere of an urban area using a scanning infrared (IR) gas system (SIGIS2, Bruker). Several measurements were carried out from 3 different positions in order to monitor an atmospheric volume around 108 m3. The images generated by the imaging remote sensing system correspond to the 2-D projections of the 3-D gas cloud. All the 2-D data are fully georeferenced (x, y, z and t). Each pixel of the 2-D images is associated to an IR spectrum, which was approximated to a linear combination of reference spectra and expressed as a coefficient of correlation (0 to 1). Data with a correlation coefficient higher than 0.75 are selected for 3-D modeling. The method for 3-D reconstruction of gas clouds is based on the combination and relocation of all the oriented and georeferenced measurement data. The 3-D gas cloud is determined from the 2-D images in the volume of interest processing a 3-D interpolation using the gOcad® DSI procedure. This integrated approach was applied to a local case study in an urban area. It leads to the identification and the spatial demarcation of a cloud of SO2 with a total volume of 65 × 106 m3. The existence of this pollutant may be related to the presence of ancient underground tanks of gasoline, leaking because of a defect of waterproofness. Another source of SO2 can be the emission of gases stemming from diesel machines used for important public works in this urban area. This study demonstrates that the combination of scanning imaging IR spectroscopy with the measurement setup and the 3-D gOcad® processing can be used as a generic approach for 3-D reconstruction of gas clouds applied to any kind of ground emissive sites.
Volcanic CO2 emissions inventories have great importance in the understanding of the geological c... more Volcanic CO2 emissions inventories have great importance in the understanding of the geological carbon cycle. Volcanoes provide the primary pathway for solid-earth volatiles to reach the Earth’s atmosphere and have the potential to significantly contribute to the carbon-climate feedback. Volcanic carbon emissions (both passive and eruptive degassing) included in inventories, largely stem from patchy surface measurements that suffer from difficulties in removing the atmospheric background. With a 27-year-long ongoing open-vent eruption, Popocatépetl ranks as one of the highest permanent volcanic CO2 emitters worldwide and provides an excellent natural laboratory to design and experiment with new remote sensing methods for volcanic gas emission measurements. Since October 2012, infrared spectra at different spectral regions have been recorded with a solar occultation FTIR spectrometer. The near-infrared spectra allow for high precision measurements of CO2 and HCl columns. Under favora...
Volcanic plume composition is strongly influenced by both changes in magmatic systems and plume-a... more Volcanic plume composition is strongly influenced by both changes in magmatic systems and plume-atmosphere interactions. Understanding the degassing mechanisms controlling the type of volcanic activity implies deciphering the contributions of magmatic gases reaching the surface and their posterior chemical transformations in contact with the atmosphere. Remote sensing techniques based on direct solar absorption spectroscopy provide valuable information about most of the emitted magmatic gases but also on gas species formed and converted within the plumes. In this study, we explore the procedures, performances and benefits of combining two direct solar absorption techniques, high resolution Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet Differential Optical Absorption Spectroscopy (UV-DOAS), to observe the composition changes in the Popocatépetl’s plume with high temporal resolution. The SO2 vertical columns obtained from three instruments (DOAS, high resolution FTIR ...
Total column H2O is measured by two remote sensing techniques at the Altzomoni Atmospheric Observ... more Total column H2O is measured by two remote sensing techniques at the Altzomoni Atmospheric Observatory (19° 12'N, 98° 65'W, 4000 m a.s.l.), a high-altitude, tropical background site in central Mexico. A ground-based solar absorption FTIR spectrometer that is part of the Network for Detection of Atmospheric Composition Change (NDACC) is used to retrieve water vapor in three spectral regions (6074-6471, 2925-2941 and 1110-1253 cm-1) and is compared to data obtained from a GPS (Global Positioning System) receiver that is part of the TLALOCNet GPS-meteorological network. Strong correlations are obtained between the coincident hourly means from the three FTIR products and small relative bias and correction factors could be determined for each when compared to the more consistent GPS data. Retrievals from the 2925-2941 cm-1 spectral region have the highest correlation with GPS (R2= 0.998, std= 0.18 cm (78.39%), mean diff= 0.04 cm (8.33%)), although the other products are also high...
<p>About seventy-five percent of the global carbon dioxide emissions from fossil fuel come ... more <p>About seventy-five percent of the global carbon dioxide emissions from fossil fuel come from cities. Reducing anthropogenic greenhouse gas emissions, in particular in developing countries, is a major concern for local, national and international policies. Different mitigation strategies are and will be implemented to reduce greenhouse gas emissions, and the evaluation of their success and their perennization depends on the ability to continuously measure and quantify the effects at different spatial and temporal scales.</p><p>Using continuous solar absorption Fourier transform Spectroscopy (FTIR) column measurements in both urban and background environments over the Mexico City metropolitan area, together with in situ datasets, we explore the spatial and temporal variability of the CO2 concentration over the 5 last years in the region. Measurements were performed from three permanent stations equipped with high and low spectral resolution FTIR spectrometers since 2012, 2016 and 2018, respectively, the first is part of the NDACC network while the other two contribute to the COCCON international initiative.</p><p>In the frame of the Mexico City&#8217;s Regional Carbon Impacts (MERCI-CO2) project, 4 complementary sites equipped with EM27/Sun instruments were temporarily implemented within the megacity since autumn 2020. In particular, our time series encompass the COVID shutdown in MCMA. In this contribution we present results of the long term measurements in background and urban environment, intercomparison measurements, and preliminary results of the temporary MERCI-CO2 stations. In addition we report about the obstacles and opportunities of this intensive measurement campaign.</p>
<p><span>Knowledge about water vapor isotopologues is a useful tool in the study of t... more <p><span>Knowledge about water vapor isotopologues is a useful tool in the study of the hydrological cycle. Total columns of water vapor isotopologues (H</span><sub><span>2</span></sub><sup><span>16</span></sup><span>O, H</span><sub><span>2</span></sub><sup><span>18</span></sup><span>O and HD</span><sup><span>16</span></sup><span>O) are measured by ground-based solar absorption FTIR spectroscopy at Altzomoni (3985 m.a.s.l, 19.12&#186;N, 98.66&#186;W), a high altitude subtropical remote background site in central Mexico (Barthlott et al., 2017). In the contribution we present the time series of the isotopic composition of water vapor columns and profiles above central Mexico and analyze differences in the isotopic ratios of H</span><sub><span>2</span></sub><sup><span>16</span></sup><span>O, H</span><sub><span>2</span></sub><sup><span>18</span></sup><span>O and HD</span><sup><span>16</span></sup><span>O between the rain and dry seasons of the year: in the rain season, changes in the isotopic ratios might be dominated by the diurnal cycle, which correlates with the relative humidity, temperature and dew point, while isotopic ratio in the dry season might depend more on the origin of the air parcels and transportation. We discuss the hydrological cycle in central Mexico using the relationship between light and heavy isotopes, and how this relationship gives valuable information about the pathways, sources and transport.</span></p>
<p>The Mexico City Metropolitan Area (MCMA), located in proximity to an active volcano, is ... more <p>The Mexico City Metropolitan Area (MCMA), located in proximity to an active volcano, is the largest urban center in North America and there is great interest to better characterize carbon emissions of this and other major urban centers in the country. NASA&#8217;s Orbiting Carbon Observatory (OCO-3) was installed in the International Space (ISS) in 2019. The inclusion of a Pointing Mirror Assembly (PMA) in this third iteration allows for a new mode of data collection that samples an area of ~80 x 80 km in approximately 2 minutes. This mode is used to collect map-like data, called Snapshot Area Maps (SAMs), over areas of interest (e.g. volcanos or urban areas). The OCO-3 module has collected SAMs over the MCMA (and the Popocat&#233;petl volcano) throughout 2020, and also of the metropolitan areas of Guadalajara and Monterrey throughout the second half of 2020.</p><p>Using data from the public release of OCO-3 Level 2 (L2) &#8220;Lite EarlyR&#8221; product, available at the Goddard Earth Sciences Data and Information Services Center (GES DISC), we have built maps of the spatial distribution of xCO<sub>2</sub> for these regions. Data is filtered according to the reported quality flag in the data product, compared with ground-based FTIR measurements of column xCO<sub>2</sub> over the MCMA region and averaged with an oversampling method. Surface pressure data with the averaged xCO<sub>2</sub> is used to calculate the concentrations within the mixed layer (xCO<sub>2</sub><sup>ML</sup>) in order to compensate for the effects of the complex terrain.&#160; This product is also used&#160; for comparison with CO spatial distributions obtained from TROPOMI data products and a simple xCO<sup>ML</sup>/xCO<sub>2</sub><sup>ML</sup> ratio is obtained and mapped for the three urban centers. This work showcases the utility of SAMs in cooperation with ground-based measurements to produce detailed descriptions of the spatial distribution of CO<sub>2</sub> for a wide variety of applications, as well as the importance of frequent soundings over important emission sources around the world.</p>
Urban areas are important contributors to the increase of global CO2 levels due to human activiti... more Urban areas are important contributors to the increase of global CO2 levels due to human activities, but continuous records of CO2 concentration in cities are scarce, especially in the developing world. In this study we present five years of simultaneous, in-situ measurements at a university campus in the south of Mexico City (UNAM) and at a high-altitude station, the Altzomoni atmospheric observatory (ALTZ), 60 km apart from the first site. The characteristics of the daily cycles, seasonality, and long-term trends were extracted from both time series. The features of the daily and seasonal cycles at UNAM are dominated by the dynamics of the boundary layer growth, while the seasonality at Altzomoni is determined by both the local meteorology and the photosynthetic activity of the vegetation. Annual CO2 growth rates of 2.4 and 2.6 ppm yr–1 were estimated for UNAM and Altzomoni, respectively, in close agreement with reported global growth rates and with previous estimates of total col...
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