Discrete-wavelength DOAS NO2 slant column retrievals from OMI and TROPOMI
Cristina Ruiz Villena, Jasdeep S. Anand, Roland J. Leigh, Paul S. Monks, Claire E. Parfitt, and Joshua D. Vande Hey
Atmos. Meas. Tech., 13, 1735–1756, https://doi.org/10.5194/amt-13-1735-2020, 2020
We present a new method to derive NO2 concentrations from satellite observations that uses up to 30 times less spectral information than traditional methods. We tested the method using data from existing instruments OMI and TROPOMI and found our results agree with the reference data to 5 % and 11 %, respectively. Our method could allow for simpler instrument designs that can be used in low-cost constellations of small satellites for air quality monitoring at high spatial and temporal resolution.
Estimates of lightning NOx production based on high-resolution OMI NO2 retrievals over the continental US
Xin Zhang, Yan Yin, Ronald van der A, Jeff L. Lapierre, Qian Chen, Xiang Kuang, Shuqi Yan, Jinghua Chen, Chuan He, and Rulin Shi
Atmos. Meas. Tech., 13, 1709–1734, https://doi.org/10.5194/amt-13-1709-2020, 2020
Lightning NOx has a strong impact on ozone and the hydroxyl radical production. However, the production efficiency of lightning NOx is still quite uncertain. This work develops the algorithm of estimating lightning NOx for both clean and polluted regions and evaluates the sensitivity of estimates to the model setting of lightning NO. Results reveal that our method reduces the sensitivity to the background NO2 and includes much of the below-cloud LNO2.
Discrete-wavelength DOAS NO2 slant column retrievals from OMI and TROPOMI
Cristina Ruiz Villena, Jasdeep S. Anand, Roland J. Leigh, Paul S. Monks, Claire E. Parfitt, and Joshua D. Vande Hey
Atmos. Meas. Tech., 13, 1735–1756, https://doi.org/10.5194/amt-13-1735-2020, 2020
We present a new method to derive NO2 concentrations from satellite observations that uses up to 30 times less spectral information than traditional methods. We tested the method using data from existing instruments OMI and TROPOMI and found our results agree with the reference data to 5 % and 11 %, respectively. Our method could allow for simpler instrument designs that can be used in low-cost constellations of small satellites for air quality monitoring at high spatial and temporal resolution.
Estimates of lightning NOx production based on high-resolution OMI NO2 retrievals over the continental US
Xin Zhang, Yan Yin, Ronald van der A, Jeff L. Lapierre, Qian Chen, Xiang Kuang, Shuqi Yan, Jinghua Chen, Chuan He, and Rulin Shi
Atmos. Meas. Tech., 13, 1709–1734, https://doi.org/10.5194/amt-13-1709-2020, 2020
Lightning NOx has a strong impact on ozone and the hydroxyl radical production. However, the production efficiency of lightning NOx is still quite uncertain. This work develops the algorithm of estimating lightning NOx for both clean and polluted regions and evaluates the sensitivity of estimates to the model setting of lightning NO. Results reveal that our method reduces the sensitivity to the background NO2 and includes much of the below-cloud LNO2.
Evaluation and calibration of a low-cost particle sensor in ambient conditions using machine-learning methods
Minxing Si, Ying Xiong, Shan Du, and Ke Du
Atmos. Meas. Tech., 13, 1693–1707, https://doi.org/10.5194/amt-13-1693-2020, 2020
The study evaluated the performance of a low-cost PM sensor in ambient conditions and calibrated its readings using simple linear regression (SLR), multiple linear regression (MLR), and two more powerful machine-learning algorithms with random search techniques for the best model architectures. The two machine-learning algorithms are XGBoost and a feedforward neural network (NN).
Retrieval and evaluation of tropospheric aerosol extinction profiles using MAX-DOAS measurements over Athens, Greece
Myrto Gratsea, Tim Bösch, Panos Kokkalis, Andreas Richter, Mihalis Vrekoussis, Stelios Kazadzis, Alexandra Tsekeri, Alexandros Papayannis, Maria Mylonaki, Vassilis Amiridis, Nikos Mihalopoulos, and Evangelos Gerasopoulos
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-100,2020
Preprint under review for AMT (discussion: open, 0 comments)
In this study, we report on the retrieval of aerosol extinction profiles from ground-based scattered sunlight multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements, carried out at Athens, Greece. It is the first time that aerosol profiles are retrieved from MAX-DOAS measurements in Athens. The reported aerosol vertical distributions at 477 nm are derived from the oxygen dimer (O4) differential slant column density observations at different elevation angles by applying the BOREAS retrieval algorithm. Four case studies have been selected for validation purposes; the retrieved aerosol profiles and the corresponding aerosol optical depths (AODs) from the MAX-DOAS are compared with lidar extinction profiles and with sun photometric measurements (AERONET observations), respectively. Despite the different approach of each method regarding the retrieval of the aerosol information, the comparison with the lidar measurements at 532 nm reveals a very good agreement in terms of vertical distribution, with r > 0.85 in all cases. The AODs from the MAX-DOAS and the sun-photometer (the latter at 500 nm) show a satisfactory correlation (with r ≈ 0.6 in three out of the four cases). The comparison indicates that the MAX-DOAS systematically underestimates the AOD in the cases of large particles (small Ångström exponent) and for measurements at small relative azimuthal angles between the viewing direction and the Sun. Better agreement is achieved in the morning, at large relative azimuthal angles. Overall, the aerosol profiles retrieved from MAX-DOAS measurements are of good quality; thus, new perspectives are opened up for assessing urban aerosol pollution on a long term-basis in Athens from continuous and uninterrupted MAX-DOAS measurements.
Evaluation and calibration of a low-cost particle sensor in ambient conditions using machine-learning methods
Minxing Si, Ying Xiong, Shan Du, and Ke Du
Atmos. Meas. Tech., 13, 1693–1707, https://doi.org/10.5194/amt-13-1693-2020, 2020
The study evaluated the performance of a low-cost PM sensor in ambient conditions and calibrated its readings using simple linear regression (SLR), multiple linear regression (MLR), and two more powerful machine-learning algorithms with random search techniques for the best model architectures. The two machine-learning algorithms are XGBoost and a feedforward neural network (NN).
Retrieval and evaluation of tropospheric aerosol extinction profiles using MAX-DOAS measurements over Athens, Greece
Myrto Gratsea, Tim Bösch, Panos Kokkalis, Andreas Richter, Mihalis Vrekoussis, Stelios Kazadzis, Alexandra Tsekeri, Alexandros Papayannis, Maria Mylonaki, Vassilis Amiridis, Nikos Mihalopoulos, and Evangelos Gerasopoulos
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-100,2020
Preprint under review for AMT (discussion: open, 0 comments)
In this study, we report on the retrieval of aerosol extinction profiles from ground-based scattered sunlight multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements, carried out at Athens, Greece. It is the first time that aerosol profiles are retrieved from MAX-DOAS measurements in Athens. The reported aerosol vertical distributions at 477 nm are derived from the oxygen dimer (O4) differential slant column density observations at different elevation angles by applying the BOREAS retrieval algorithm. Four case studies have been selected for validation purposes; the retrieved aerosol profiles and the corresponding aerosol optical depths (AODs) from the MAX-DOAS are compared with lidar extinction profiles and with sun photometric measurements (AERONET observations), respectively. Despite the different approach of each method regarding the retrieval of the aerosol information, the comparison with the lidar measurements at 532 nm reveals a very good agreement in terms of vertical distribution, with r > 0.85 in all cases. The AODs from the MAX-DOAS and the sun-photometer (the latter at 500 nm) show a satisfactory correlation (with r ≈ 0.6 in three out of the four cases). The comparison indicates that the MAX-DOAS systematically underestimates the AOD in the cases of large particles (small Ångström exponent) and for measurements at small relative azimuthal angles between the viewing direction and the Sun. Better agreement is achieved in the morning, at large relative azimuthal angles. Overall, the aerosol profiles retrieved from MAX-DOAS measurements are of good quality; thus, new perspectives are opened up for assessing urban aerosol pollution on a long term-basis in Athens from continuous and uninterrupted MAX-DOAS measurements.
Mixing height derivation from aerosol lidar using machine learning: KABL and ADABL algorithms
Thomas Rieutord, Sylvain Aubert, and Tiago Machado
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-78,2020
Preprint under review for AMT (discussion: open, 0 comments)
This article describes two methods to estimate the height of the very first layer of atmosphere. It is measured with aerosol lidars and the two new methods are based on machine learning. Both are open source and under free license. A sensitivity analysis and a 2-years evaluation against meteorological balloons were carried out. One method has a good agreement with balloons but is limited by training and the other has less good agreement with balloons but is more flexible.
A compact QCL spectrometer for mobile, high-precision methane sensing aboard drones
Béla Tuzson, Manuel Graf, Jonas Ravelid, Philipp Scheidegger, André Kupferschmid, Herbert Looser, Randulph Paulo Morales, and Lukas Emmenegger
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-102,2020
Preprint under review for AMT (discussion: open, 0 comments)
We describe a lightweight (2 kg) mid-IR laser spectrometer for airborne, in situ atmospheric methane (CH4) measurements. The instrument, based on an open-path circular multipass cell, provides fast response (1 Hz) and sub-ppb precision. It can easily be mounted on a drone, giving access to highly resolved 4 D (spatial and temporal) data. The performance was assessed during field deployments involving artificial CH4 sources and vertical concentration gradients in the PBL.
Mixing height derivation from aerosol lidar using machine learning: KABL and ADABL algorithms
Thomas Rieutord, Sylvain Aubert, and Tiago Machado
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-78,2020
Preprint under review for AMT (discussion: open, 0 comments)
This article describes two methods to estimate the height of the very first layer of atmosphere. It is measured with aerosol lidars and the two new methods are based on machine learning. Both are open source and under free license. A sensitivity analysis and a 2-years evaluation against meteorological balloons were carried out. One method has a good agreement with balloons but is limited by training and the other has less good agreement with balloons but is more flexible.
A compact QCL spectrometer for mobile, high-precision methane sensing aboard drones
Béla Tuzson, Manuel Graf, Jonas Ravelid, Philipp Scheidegger, André Kupferschmid, Herbert Looser, Randulph Paulo Morales, and Lukas Emmenegger
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-102,2020
Preprint under review for AMT (discussion: open, 0 comments)
We describe a lightweight (2 kg) mid-IR laser spectrometer for airborne, in situ atmospheric methane (CH4) measurements. The instrument, based on an open-path circular multipass cell, provides fast response (1 Hz) and sub-ppb precision. It can easily be mounted on a drone, giving access to highly resolved 4 D (spatial and temporal) data. The performance was assessed during field deployments involving artificial CH4 sources and vertical concentration gradients in the PBL.
Surface flux estimates derived from UAS-based mole fraction measurements by means of a nocturnal boundary layer budget approach
Martin Kunz, Jost V. Lavric, Rainer Gasche, Christoph Gerbig, Richard H. Grant, Frank-Thomas Koch, Marcus Schumacher, Benjamin Wolf, and Matthias Zeeman
Atmos. Meas. Tech., 13, 1671–1692, https://doi.org/10.5194/amt-13-1671-2020, 2020
The nocturnal boundary layer (NBL) budget method enables the quantification of gas fluxes between ecosystems and the atmosphere under nocturnal stable stratification, a condition under which standard approaches struggle. However, up to now the application of the NBL method has been limited by difficulties in obtaining the required measurements. We show how an unmanned aircraft system (UAS) equipped with a carbon dioxide analyser can make this method more accessible.
A new method to correct the ECC ozone sonde time response and its implications for “background current” and pump efficiency
Holger Vömel, Herman G. J. Smit, David Tarasick, Bryan Johnson, Samuel J. Oltmans, Henry Selkirk, Anne M. Thompson, Ryan M. Stauffer, Jacquelyn C. Witte, Jonathan Davies, Roeland van Malderen, Gary A. Morris, Tatsumi Nakano, and Rene Stübi
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-62,2020
Preprint under review for AMT (discussion: open, 0 comments)
The time response of Electrochemical Concentration Cell (ECC) ozone sondes points to at least two distinct reaction pathways with time constants of approximately 20 s and 25 min. Properly considering these time constants eliminates the need for a poorly defined "background" and allows reducing ad-hoc corrections based on laboratory tests. This reduces the uncertainty of ECC ozone sonde measurements throughout the profile and especially in regions of low ozone and strong gradients of ozone.
In-orbit Earth reflectance validation of TROPOMI on board the Sentinel-5 Precursor satellite
Lieuwe G. Tilstra, Martin de Graaf, Ping Wang, and Piet Stammes
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-98,2020
Preprint under review for AMT (discussion: open, 0 comments)
The goal of the study was to determine the accuracy of the radiometric calibration of the TROPOMI instrument on board the Sentinel-5 Precursor satellite in-flight. The Earth reflectances were compared to radiative transfer calculations. We report calibration accuracies and errors for 21 selected wavelength bands between 328 and 2314 nm, located in TROPOMI spectral bands 3–7. The reported numbers can be used to perform corrections that will benefit the retrievals of many atmospheric properties.
Surface flux estimates derived from UAS-based mole fraction measurements by means of a nocturnal boundary layer budget approach
Martin Kunz, Jost V. Lavric, Rainer Gasche, Christoph Gerbig, Richard H. Grant, Frank-Thomas Koch, Marcus Schumacher, Benjamin Wolf, and Matthias Zeeman
Atmos. Meas. Tech., 13, 1671–1692, https://doi.org/10.5194/amt-13-1671-2020, 2020
The nocturnal boundary layer (NBL) budget method enables the quantification of gas fluxes between ecosystems and the atmosphere under nocturnal stable stratification, a condition under which standard approaches struggle. However, up to now the application of the NBL method has been limited by difficulties in obtaining the required measurements. We show how an unmanned aircraft system (UAS) equipped with a carbon dioxide analyser can make this method more accessible.
A new method to correct the ECC ozone sonde time response and its implications for “background current” and pump efficiency
Holger Vömel, Herman G. J. Smit, David Tarasick, Bryan Johnson, Samuel J. Oltmans, Henry Selkirk, Anne M. Thompson, Ryan M. Stauffer, Jacquelyn C. Witte, Jonathan Davies, Roeland van Malderen, Gary A. Morris, Tatsumi Nakano, and Rene Stübi
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-62,2020
Preprint under review for AMT (discussion: open, 0 comments)
The time response of Electrochemical Concentration Cell (ECC) ozone sondes points to at least two distinct reaction pathways with time constants of approximately 20 s and 25 min. Properly considering these time constants eliminates the need for a poorly defined "background" and allows reducing ad-hoc corrections based on laboratory tests. This reduces the uncertainty of ECC ozone sonde measurements throughout the profile and especially in regions of low ozone and strong gradients of ozone.
In-orbit Earth reflectance validation of TROPOMI on board the Sentinel-5 Precursor satellite
Lieuwe G. Tilstra, Martin de Graaf, Ping Wang, and Piet Stammes
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-98,2020
Preprint under review for AMT (discussion: open, 0 comments)
The goal of the study was to determine the accuracy of the radiometric calibration of the TROPOMI instrument on board the Sentinel-5 Precursor satellite in-flight. The Earth reflectances were compared to radiative transfer calculations. We report calibration accuracies and errors for 21 selected wavelength bands between 328 and 2314 nm, located in TROPOMI spectral bands 3–7. The reported numbers can be used to perform corrections that will benefit the retrievals of many atmospheric properties.
An instrument for in situ measurement of total ozone reactivity
Roberto Sommariva, Louisa J. Kramer, Leigh R. Crilley, Mohammed S. Alam, and William J. Bloss
Atmos. Meas. Tech., 13, 1655–1670, https://doi.org/10.5194/amt-13-1655-2020, 2020
Ozone is a key atmospheric pollutant formed through chemical processing of natural and anthropogenic emissions and removed by reaction with organic compounds emitted by plants. We describe a new instrument – the Total Ozone Reactivity System or TORS – that measures the total loss of ozone in the troposphere. The objective of the TORS instrument is to provide an estimate of the organic compounds emitted by plants which are not measured and thus to improve our understanding of the ozone budget.
Comparison of GTO-ECV and adjusted MERRA-2 total ozone columns from the last 2 decades and assessment of interannual variability
Melanie Coldewey-Egbers, Diego G. Loyola, Gordon Labow, and Stacey M. Frith
Atmos. Meas. Tech., 13, 1633–1654, https://doi.org/10.5194/amt-13-1633-2020, 2020
We compare total ozone columns from the satellite-based GOME-type Total Ozone Essential Climate Variable record and the adjusted Modern Era Retrospective Analysis for Research and Applications version 2 reanalysis during their overlap period from 1995 to 2018. Ozone columns and anomalies show a very good agreement in terms of spatial and temporal patterns. In the tropics the interannual variability is assessed by means of an EOF analysis and both data records show a remarkable consistency.
