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1. On the effect of sea breeze regime on aerosols and gases properties in the urban area of Rome, Italy

Author: Di Bernardino, Annalisa, Iannarelli, Anna Maria, Casadio, Stefano, Mevi, Gabriele, Campanelli, Monica, Casasanta, Giampietro, Cede, Alexander, Tiefengraber, Martin, Siani, Anna Maria, Spinei, Elena, and Cacciani, Marco
Published: 2021
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2. Comparisons of Spectral Aerosol Single Scattering Albedo in Seoul, South Korea

Author: Mok, Jungbin, Krotkov, Nickolay A, Torres, Omar, Jethva, Hiren, Li, Zhanqing, Kim, Jhoon, Koo, Ja-Ho, Go, Sujung, Irie, Hitoshi, Labow, Gordon, Eck, Thomas F, Holben, Brent N, Herman, Jay, Loughman, Robert P, Spinei, Elena, Lee, Seoung Soo, Khatri, Pradeep, and Campanelli, Monica
Subjects: Environment Pollution
Abstract: Quantifying aerosol absorption at ultraviolet (UV) wavelengths is important for monitoring air pollution and aerosol amounts using current (e.g., Aura/OMI (Ozone Monitoring Instrument)) and future (e.g., TROPOMI (TROPOspheric Monitoring Instrument), TEMPO (Tropospheric Emissions: Monitoring of POllution), GEMS (Geostationary Environment Monitoring Spectrometer) and Sentinel-4) satellite measurements. Measurements of column average atmospheric aerosol single scattering albedo (SSA) are performed on the ground by the NASA AERONET (AEROsol robotic NETwork) in the visible (VIS) and near-infrared (NIR) wavelengths and in the UV-VIS-NIR by the SKYNET (SKY radiometer NETwork) networks. Previous comparison studies have focused on VIS and NIR wavelengths due to the lack of co-incident measurements of aerosol and gaseous absorption properties in the UV. This study compares the SKYNET-retrieved SSA in the UV with the SSA derived from a combination of AERONET, MFRSR (MultiFilter Rotating Shadowband Radiometer), and Pandora (AMP) retrievals in Seoul, South Korea, in spring and summer 2016. The results show that the spectrally invariant surface albedo assumed in the SKYNET SSA retrievals leads to underestimated SSA compared to AMP values at near UV wavelengths. Re-processed SKYNET inversions using spectrally varying surface albedo, consistent with the AERONET retrieval improve agreement with AMP SSA. The combined AMP inversions allow for separating aerosol and gaseous (NO2 and O3) absorption and provide aerosol retrievals from the shortest UVB (305 nanometers) through VIS to NIR wavelengths (870 nanometers).
Published: 2018
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3. Can Column Formaldehyde Observations Inform Air Quality Monitoring Strategies for Ozone and Related Photochemical Oxidants?

Author: Travis, K. R., primary, Judd, L. M., additional, Crawford, J. H., additional, Chen, Gao, additional, Szykman, James, additional, Whitehill, Andrew, additional, Valin, Lukas C., additional, Spinei, Elena, additional, Janz, Scott, additional, Nowlan, Caroline R., additional, Kwon, Hyeong‐Ahn, additional, Fried, Alan, additional, and Walega, James, additional
Published: 2022
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4. Can Column Formaldehyde Observations Inform Air Quality Monitoring Strategies for Ozone and Related Photochemical Oxidants?

Author: Travis, K. R., Judd, L. M., Crawford, J. H., Chen, Gao, Szykman, James, Whitehill, Andrew, Valin, Lukas C., Spinei, Elena, Janz, Scott, Nowlan, Caroline R., Kwon, Hyeong-Ahn, Fried, Alan, Walega, James, Travis, K. R., Judd, L. M., Crawford, J. H., Chen, Gao, Szykman, James, Whitehill, Andrew, Valin, Lukas C., Spinei, Elena, Janz, Scott, Nowlan, Caroline R., Kwon, Hyeong-Ahn, Fried, Alan, and Walega, James
Abstract: Formaldehyde column density (omega HCHO) showed a potentially useful correlation with surface ozone during the LISTOS campaign on Long Island Sound and the KORUS-AQ campaign in Seoul, South Korea. This builds on previous work that identified this relationship from in situ aircraft observations with similar findings for ground-based and airborne remote sensing of omega HCHO. In the Long Island Sound region, omega HCHO and surface ozone exhibited strong temporal (r(2) = 0.66) and spatial (r(2) = 0.73) correlation. The temporal variability in omega HCHO (similar to 1 Dobson units [DU]) was larger than the range in the spatial average (similar to 0.1 DU). The spatial average is most useful for informing ozone monitoring strategies, demonstrating the challenge in using omega HCHO satellite data sets for this purpose. In Seoul, high levels of NO2 resulted in O-x better correlating with omega HCHO than surface ozone due to titration effects. The omega HCHO-O-x relationship may therefore reflect the sum of surface ozone and related photochemical oxidants, relevant to air quality standards set to regulate this quantity such as the U.S. EPA National Ambient Air Quality Standard (NAAQS). The relationship of omega HCHO to O-x shifted in Seoul during the campaign demonstrating the need to evaluate this relationship over longer time periods. With sufficient precision in future satellite retrievals, omega HCHO observations could be useful for evaluating the adequacy of surface air quality monitoring strategies.
Published: 2022

5. Effect of polyoxymethylene (POM-H Delrin) off-gassing within the Pandora head sensor on direct-sun and multi-axis formaldehyde column measurements in 2016-2019

Author: Center for Space Science and Engineering Research, Spinei, Elena, Tiefengraber, Martin, Mueller, Moritz, Gebetsberger, Manuel, Cede, Alexander, Valin, Luke, Szykman, James, Whitehill, Andrew, Kotsakis, Alexander, Santos, Fernando, Abbuhasan, Nader, Zhao, Xiaoyi, Fioletov, Vitali, Lee, Sum Chi, Swap, Robert, Center for Space Science and Engineering Research, Spinei, Elena, Tiefengraber, Martin, Mueller, Moritz, Gebetsberger, Manuel, Cede, Alexander, Valin, Luke, Szykman, James, Whitehill, Andrew, Kotsakis, Alexander, Santos, Fernando, Abbuhasan, Nader, Zhao, Xiaoyi, Fioletov, Vitali, Lee, Sum Chi, and Swap, Robert
Abstract: Analysis of formaldehyde measurements by the Pandora spectrometer systems between 2016 and 2019 suggested that there was a temperature-dependent process inside the Pandora head sensor that emitted formaldehyde. Some parts in the head sensor were manufactured from the thermal plastic polyoxymethylene homopolymer (E.I. Du Pont de Nemour & Co., USA; POM-H Delrin (R)) and were responsible for formaldehyde production. Laboratory analysis of the four Pandora head sensors showed that internal formaldehyde production had exponential temperature dependence with a damping coefficient of 0.0911 +/- 0.0024 degrees C-1 and the exponential function amplitude ranging from 0.0041 to 0.049 DU. No apparent dependency on the head sensor age and heating and cooling rates was detected. The total amount of formaldehyde internally generated by the POM-H Delrin components and contributing to the direct-sun measurements were estimated based on the head sensor temperature and solar zenith angle of the measurements. Measurements in winter, during colder (< 10 degrees C) days in general, and at high solar zenith angles (> 75 degrees) were minimally impacted. Measurements during hot days (> 28 degrees C) and small solar zenith angles had up to 1 DU (2.69 x 10(16 )molec. cm(-2)) contribution from POM-H Delrin parts. Multi-axis differential slant column densities were minimally impacted (< 0.01 DU) due to the reference spectrum being collected within a short time period with a small difference in head sensor temperature. Three new POM-H Delrin free Pandora head sensors (manufactured in summer 2019) were evaluated for temperature-dependent attenuation across the entire spectral range (300 to 530 nm). No formaldehyde absorption or any other absorption above the instrumental noise was observed across the entire spectral range.
Published: 2021

6. Intercomparison of NO2, O-4, O-3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV-visible spectrometers during CINDI-2

Author: Kreher, Karin, Van Roozendael, Michel, Hendrick, Francois, Apituley, Arnoud, Dimitropoulou, Ermioni, Friess, Udo, Richter, Andreas, Wagner, Thomas, Lampel, Johannes, Abuhassan, Nader, Ang, Li, Anguas, Monica, Bais, Alkis, Benavent, Nuria, Boesch, Tim, Bognar, Kristof, Borovski, Alexander, Bruchkouski, Ilya, Cede, Alexander, Chan, Ka Lok, Donner, Sebastian, Drosoglou, Theano, Fayt, Caroline, Finkenzeller, Henning, Garcia-Nieto, David, Gielen, Clio, Gomez-Martin, Laura, Hao, Nan, Henzing, Bas, Herman, Jay R., Hermans, Christian, Hoque, Syedul, Irie, Hitoshi, Jin, Junli, Johnston, Paul, Butt, Junaid Khayyam, Khokhar, Fahim, Koenig, Theodore K., Kuhn, Jonas, Kumar, Vinod, Liu, Cheng, Ma, Jianzhong, Merlaud, Alexis, Mishra, Abhishek K., Mueller, Moritz, Navarro-Comas, Monica, Ostendorf, Mareike, Pazmino, Andrea, Peters, Enno, Pinardi, Gaia, Pinharanda, Manuel, Piters, Ankie, Platt, Ulrich, Postylyakov, Oleg, Prados-Roman, Cristina, Puentedura, Olga, Querel, Richard, Saiz-Lopez, Alfonso, Schoenhardt, Anja, Schreier, Stefan F., Seyler, Andre, Sinha, Vinayak, Spinei, Elena, Strong, Kimberly, Tack, Frederik, Tian, Xin, Tiefengraber, Martin, Tirpitz, Jan-Lukas, van Gent, Jeron, Volkamer, Rainer, Vrekoussis, Mihalis, Wang, Shanshan, Wang, Zhuoru, Wenig, Mark, Wittrock, Folkard, Xie, Pinhua H., Xu, Jin, Yela, Margarita, Zhang, Chengxin, Zhao, Xiaoyi, BK Scientific GmbH, Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Royal Netherlands Meteorological Institute (KNMI), Institut für Umweltphysik [Heidelberg], Universität Heidelberg [Heidelberg], Institute of Environmental Physics [Bremen] (IUP), University of Bremen, Max-Planck-Institut für Chemie (MPIC), Max-Planck-Gesellschaft, NASA Goddard Space Flight Center (GSFC), Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences [Changchun Branch] (CAS), Instituto de Química Física Rocasolano (IQFR), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Laboratory of Atmospheric Physics [Thessaloniki], Aristotle University of Thessaloniki, Department of Physics [Toronto], University of Toronto, A.M.Obukhov Institute of Atmospheric Physics (IAP), Russian Academy of Sciences [Moscow] (RAS), Belarusian State University, Meteorologisches Institut München (MIM), Ludwig-Maximilians-Universität München (LMU), School of Earth and Space Sciences [Hefei], University of Science and Technology of China [Hefei] (USTC), Department of Chemistry and Biochemistry [Boulder], University of Colorado [Boulder], Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado [Boulder]-National Oceanic and Atmospheric Administration (NOAA), Instituto Nacional de Técnica Aeroespacial (INTA), European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), The Netherlands Organisation for Applied Scientific Research (TNO), Center for Environmental Remote Sensing [Chiba] (CEReS), Chiba University, Chinese Academy of Meteorological Sciences (CAMS), National Institute of Water and Atmospheric Research [Lauder] (NIWA), National University of Sciences and Technology [Islamabad] (NUST), Institute of Environmental Physics [Heidelberg] (IUP), Indian Institute of Science Education and Research Mohali (IISER Mohali), Department of Earth and Environmental Sciences [Mohali], Department of Atmospheric and Cryospheric Sciences [Innsbruck] (ACINN), Universität Innsbruck [Innsbruck], STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institute for the Protection of Maritime Infrastructures, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institute for Meteorology and Climatology [Vienna] (BOKU-Met), University of Natural Resources and Life Sciences (BOKU), Virginia Polytechnic Institute and State University [Blacksburg], Center for Marine Environmental Sciences [Bremen] (MARUM), Universität Bremen, Energy, Environment and Water Research Center (EEWRC), Cyprus Institute (CyI), Liaoning Technical University [Huludao], Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Fudan University [Shanghai], DLR Institut für Methodik der Fernerkundung / DLR Remote Sensing Technology Institute (IMF), Deutsches Zentrum für Luft- und Raumfahrt [Oberpfaffenhofen-Wessling] (DLR), Environment and Climate Change Canada, and Electrical and Computer Engineering
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Science & Technology, RAMAN-SCATTERING, RETRIEVAL, CROSS-SECTIONS, BRO, RADIATIVE-TRANSFER, Physical Sciences, Meteorology & Atmospheric Sciences, OPTICAL-ABSORPTION SPECTROSCOPY, FORMALDEHYDE, CAMPAIGN, NITROGEN-DIOXIDE, AEROSOL EXTINCTION
Abstract: In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17 d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97 degrees N, 4.93 degrees E). We report on the outcome of the formal semi-blind intercomparison exercise, which was held under the umbrella of the Network for the Detection of Atmospheric Composition Change (NDACC) and the European Space Agency (ESA). The three major goals of CINDI-2 were (1) to characterise and better understand the differences between a large number of multi-axis differential optical absorption spectroscopy (MAX-DOAS) and zenith-sky DOAS instruments and analysis methods, (2) to define a robust methodology for performance assessment of all participating instruments, and (3) to contribute to a harmonisation of the measurement settings and retrieval methods. This, in turn, creates the capability to produce consistent high-quality ground-based data sets, which are an essential requirement to generate reliable long-term measurement time series suitable for trend analysis and satellite data validation. The data products investigated during the semi-blind intercomparison are slant columns of nitrogen dioxide (NO2), the oxygen collision complex (O-4) and ozone (O-3) measured in the UV and visible wavelength region, formaldehyde (HCHO) in the UV spectral region, and NO2 in an additional (smaller) wavelength range in the visible region. The campaign design and implementation processes are discussed in detail including the measurement protocol, calibration procedures and slant column retrieval settings. Strong emphasis was put on the careful alignment and synchronisation of the measurement systems, resulting in a unique set of measurements made under highly comparable air mass conditions. The CINDI-2 data sets were investigated using a regression analysis of the slant columns measured by each instrument and for each of the target data products. The slope and intercept of the regression analysis respectively quantify the mean systematic bias and offset of the individual data sets against the selected reference (which is obtained from the median of either all data sets or a subset), and the rms error provides an estimate of the measurement noise or dispersion. These three criteria are examined and for each of the parameters and each of the data products, performance thresholds are set and applied to all the measurements. The approach presented here has been developed based on heritage from previous intercomparison exercises. It introduces a quantitative assessment of the consistency between all the participating instruments for the MAX-DOAS and zenith-sky DOAS techniques. Netherlands Space Office (NSO); ESA through the CINDI-2 (ESA) project [4000118533/16/I-Sbo]; ESA through the FRM4DOAS (ESA) project [4000118181/16/I-EF]; EU 7th Framework Programme QA4ECV projectEuropean Union (EU) [607405]; Austrian Science Fund (FWF)Austrian Science Fund (FWF) [I 2296-N29]; Canadian Space Agency (AVATARS project); Natural Sciences and Engineering Research Council (PAHA project); Canada Foundation for InnovationCanada Foundation for Innovation; UVAS ("Ultraviolet and Visible Atmospheric Sounder") projects SEOSAT/INGENIO [ESP2015-71299-R]; DFG project RAPSODI [PL 193/17-1]; Centre National de la Recherche Scientifique (CNRS)Centre National de la Recherche Scientifique (CNRS); Centre National d'Etudes Spatiales (CNES)Centre National D'etudes Spatiales; National funding project HELADO [CTM2013-41311-P]; National funding project AVATAR [CGL2014-55230-R]; Russian Science FoundationRussian Science Foundation (RSF) [16-17-10275]; Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [16-05-01062, 18-35-00682]; ACTRIS-2 (H2020 grant) [654109]; NASA's Atmospheric Composition ProgramNational Aeronautics & Space Administration (NASA) [NASA-16-NUP2016-0001]; US National Science FoundationNational Science Foundation (NSF) [AGS-1620530]; NASANational Aeronautics & Space Administration (NASA); University of Bremen; DFG Research Center/Cluster of Excellence "The Ocean in the Earth System-MARUM"German Research Foundation (DFG); University of Bremen Institutional Strategy of the DFG; Luftblick through the ESA Pandonia Project; NASA Pandora Project at the Goddard Space Flight Center under NASA Headquarters' Tropospheric Composition Program CINDI-2 received funding from the Netherlands Space Office (NSO). Funding for this study was provided by ESA through the CINDI-2 (ESA contract no. 4000118533/16/I-Sbo) and FRM4DOAS (ESA contract no. 4000118181/16/I-EF) projects and partly within the EU 7th Framework Programme QA4ECV project (grant agreement no. 607405). The BOKU MAX-DOAS instrument was funded and the participation of Stefan F. Schreier was supported by the Austrian Science Fund (FWF): I 2296-N29. The participation of the University of Toronto team was supported by the Canadian Space Agency (through the AVATARS project) and the Natural Sciences and Engineering Research Council (through the PAHA project). The instrument was primarily funded by the Canada Foundation for Innovation and is usually operated at the Polar Environment Atmospheric Research Laboratory (PEARL) by the Canadian Network for the Detection of Atmospheric Change (CANDAC). Funding for CISC was provided by the UVAS ("Ultraviolet and Visible Atmospheric Sounder") projects SEOSAT/INGENIO, ESP2015-71299-R, MINECO-FEDER and UE. The activities of the IUP-Heidelberg were supported by the DFG project RAPSODI (grant no. PL 193/17-1). SAOZ and Mini-SAOZ instruments are supported by the Centre National de la Recherche Scientifique (CNRS) and the Centre National d'Etudes Spatiales (CNES). INTA recognises support from the National funding projects HELADO (CTM2013-41311-P) and AVATAR (CGL2014-55230-R). AMOIAP recognises support from the Russian Science Foundation (grant no. 16-17-10275) and the Russian Foundation for Basic Research (grant nos. 16-05-01062 and 18-35-00682). Ka L. Chan received transnational access funding from ACTRIS-2 (H2020 grant agreement no. 654109). Rainer Volkamer recognises funding from NASA's Atmospheric Composition Program (NASA-16-NUP2016-0001) and the US National Science Foundation (award AGS-1620530). Henning Finkenzeller is the recipient of a NASA graduate fellowship. Mihalis Vrekoussis recognises support from the University of Bremen and the DFG Research Center/Cluster of Excellence "The Ocean in the Earth System-MARUM". Financial support through the University of Bremen Institutional Strategy in the framework of the DFG Excellence Initiative is gratefully appreciated for Anja Schonhardt. Pandora instrument deployment was supported by Luftblick through the ESA Pandonia Project and NASA Pandora Project at the Goddard Space Flight Center under NASA Headquarters' Tropospheric Composition Program. The article processing charges for this open-access publication were covered by BK Scientific.
Published: 2020

7. Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV¿visible spectrometers during CINDI-2

Author: Kreher, Karin, Roozendael, Michel van, Hendrick, Francois, Apituley, Arnoud, Dimitropoulou, Ermioni, Frieß, Udo, Richter, Andreas, Wagner, Thomas, Lampel, Johannes, Abuhassan, Nader, Ang, Li, Anguas, Mónica, Bais, Alkis, Benavent, N., Bösch, Tim, Bognar, Kristof, Borovski, Alexander, Bruchkouski, Ilya, Cede, Alexander, Lok Chan, Ka, Donner, Sebastian, Drosoglou, Theano, Fayt, Caroline, Finkenzeller, Henning, García-Nieto, D., Gielen, Clio, Gómez-Martín, L., Hao, Nan, Henzing, Bas, Herman, Jay R., Hermans, Christian, Hoque, Syedul, Iri, Hitoshi, Jin, Junli, Johnsto, Paul, Khayyam But, Junaid, Khokhar, Fahim, Koenig, T.K., Kuhn, Jonas, Kumar, Vinod, Li, Cheng, Ma, Jianzhong, Merlaud, Alexis, Mishra, A.K., Müller, Moritz, Navarro-Comas, M., Ostendorf, M., Pazmin, Andrea, Peters, Enno, Pinardi, Gaia, Pinharanda, M., Piters, Ankie, Platt, Ulrich, Postylyakov, Oleg, Prados-Roman, C., Puentedura, Olga, Querel, Richard, Saiz-Lopez, A., Schönhardt, A., Schreier, S.F., Seyler, André, Sinha, V., Spinei, Elena, Strong, K., Tack, F., Tian, Xin, Tiefengraber, M., Tirpitz, J.-L., Gent, J. van, Volkamer, R., Vrekoussis, M., Wang, Shanshan, Wang, Zhuoru, Wenig, Mark, Wittrock, F., Xie, P.H., Xu, Jin, Yela, M., Zhang, Chengxin, Zhao, Xiaoyi, Netherlands Space Office, European Space Agency, European Commission, Austrian Science Fund, University of Toronto, Canadian Space Agency, Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, Consejo Superior de Investigaciones Científicas (España), Ministerio de Economía y Competitividad (España), German Research Foundation, Centre National de la Recherche Scientifique (France), Centre National D'Etudes Spatiales (France), Russian Science Foundation, Russian Foundation for Basic Research, National Aeronautics and Space Administration (US), National Science Foundation (US), University of Bremen, and NASA's Goddard Space Flight Center
Abstract: 40 pags., 22 figs., 13 tabs., In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17¿d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97¿¿N, 4.93¿¿E). We report on the outcome of the formal semi-blind intercomparison exercise, which was held under the umbrella of the Network for the Detection of Atmospheric Composition Change (NDACC) and the European Space Agency (ESA). The three major goals of CINDI-2 were (1) to characterise and better understand the differences between a large number of multi-axis differential optical absorption spectroscopy (MAX-DOAS) and zenith-sky DOAS instruments and analysis methods, (2) to define a robust methodology for performance assessment of all participating instruments, and (3) to contribute to a harmonisation of the measurement settings and retrieval methods. This, in turn, creates the capability to produce consistent high-quality ground-based data sets, which are an essential requirement to generate reliable long-term measurement time series suitable for trend analysis and satellite data validation. The data products investigated during the semi-blind intercomparison are slant columns of nitrogen dioxide (NO2), the oxygen collision complex (O4) and ozone (O3) measured in the UV and visible wavelength region, formaldehyde (HCHO) in the UV spectral region, and NO2 in an additional (smaller) wavelength range in the visible region. The campaign design and implementation processes are discussed in detail including the measurement protocol, calibration procedures and slant column retrieval settings. Strong emphasis was put on the careful alignment and synchronisation of the measurement systems, resulting in a unique set of measurements made under highly comparable air mass conditions. The CINDI-2 data sets were investigated using a regression analysis of the slant columns measured by each instrument and for each of the target data products. The slope and intercept of the regression analysis respectively quantify the mean systematic bias and offset of the individual data sets against the selected reference (which is obtained from the median of either all data sets or a subset), and the rms error provides an estimate of the measurement noise or dispersion. These three criteria are examined and for each of the parameters and each of the data products, performance thresholds are set and applied to all the measurements. The approach presented here has been developed based on heritage from previous intercomparison exercises. It introduces a quantitative assessment of the consistency between all the participating instruments for the MAX-DOAS and zenith-sky DOAS techniques., CINDI-2 received funding from the Netherlands Space Office (NSO). Funding for this study was provided by ESA through the CINDI-2 (ESA contract no. 4000118533/16/ISbo) and FRM4DOAS (ESA contract no. 4000118181/16/I-EF) projects and partly within the EU 7th Framework Programme QA4ECV project (grant agreement no. 607405). The BOKU MAX-DOAS instrument was funded and the participation of Stefan F. Schreier was supported by the Austrian Science Fund (FWF): I 2296-N29. The participation of the University of Toronto team was supported by the Canadian Space Agency (through the AVATARS project) and the Natural Sciences and Engineering Research Council (through the PAHA project). The instrument was primarily funded by the Canada Foundation for Innovation and is usually operated at the Polar Environment Atmospheric Research Laboratory (PEARL) by the Canadian Network for the Detection of Atmospheric Change (CANDAC). Funding for CISC was provided by the UVAS (“Ultraviolet and Visible Atmospheric Sounder”) projects SEOSAT/INGENIO, ESP2015-71299- R, MINECO-FEDER and UE. The activities of the IUP-Heidelberg were supported by the DFG project RAPSODI (grant no. PL 193/17-1). SAOZ and Mini-SAOZ instruments are supported by the Centre National de la Recherche Scientifique (CNRS) and the Centre National d’Etudes Spatiales (CNES). INTA recognises support from the National funding projects HELADO (CTM2013-41311-P) and AVATAR (CGL2014-55230-R). AMOIAP recognises support from the Russian Science Foundation (grant no. 16-17-10275) and the Russian Foundation for Basic Research (grant nos. 16-05- 01062 and 18-35-00682). Ka L. Chan received transnational access funding from ACTRIS-2 (H2020 grant agreement no. 654109). Rainer Volkamer recognises funding from NASA’s Atmospheric Composition Program (NASA-16-NUP2016-0001) and the US National Science Foundation (award AGS-1620530). Henning Finkenzeller is the recipient of a NASA graduate fellowship. Mihalis Vrekoussis recognises support from the University of Bremen and the DFG Research Center/Cluster of Excellence “The Ocean in the Earth System-MARUM”. Financial support through the University of Bremen Institutional Strategy in the framework of the DFG Excellence Initiative is gratefully appreciated for Anja Schönhardt. Pandora instrument deployment was supported by Luftblick through the ESA Pandonia Project and NASA Pandora Project at the Goddard Space Flight Center under NASA Headquarters’ Tropospheric Composition Program. The article processing charges for this open-access publication were covered by BK Scientific.
Published: 2020

8. Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV¿visible spectrometers during CINDI-2

Author: Netherlands Space Office, European Space Agency, European Commission, Austrian Science Fund, University of Toronto, Canadian Space Agency, Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, Consejo Superior de Investigaciones Científicas (España), Ministerio de Economía y Competitividad (España), German Research Foundation, Centre National de la Recherche Scientifique (France), Centre National D'Etudes Spatiales (France), Russian Science Foundation, Russian Foundation for Basic Research, National Aeronautics and Space Administration (US), National Science Foundation (US), University of Bremen, NASA's Goddard Space Flight Center, Kreher, Karin, Roozendael, Michel van, Hendrick, Francois, Apituley, Arnoud, Dimitropoulou, Ermioni, Frieß, Udo, Richter, Andreas, Wagner, Thomas, Lampel, Johannes, Abuhassan, Nader, Ang, Li, Anguas, Mónica, Bais, Alkis, Benavent, Nuria, Bösch, Tim, Bognar, Kristof, Borovski, Alexander, Bruchkouski, Ilya, Cede, Alexander, Lok Chan, Ka, Donner, Sebastian, Drosoglou, Theano, Fayt, Caroline, Finkenzeller, Henning, García-Nieto, D., Gielen, Clio, Gómez-Martín, L., Hao, Nan, Henzing, Bas, Herman, Jay R., Hermans, Christian, Hoque, Syedul, Iri, Hitoshi, Jin, Junli, Johnsto, Paul, Khayyam But, Junaid, Khokhar, Fahim, Koenig, T.K., Kuhn, Jonas, Kumar, Vinod, Li, Cheng, Ma, Jianzhong, Merlaud, Alexis, Mishra, A.K., Müller, Moritz, Navarro-Comas, M., Ostendorf, M., Pazmin, Andrea, Peters, Enno, Pinardi, Gaia, Pinharanda, M., Piters, Ankie, Platt, Ulrich, Postylyakov, Oleg, Prados-Roman, C., Puentedura, Olga, Querel, Richard, Saiz-Lopez, A., Schönhardt, A., Schreier, S.F., Seyler, André, Sinha, V., Spinei, Elena, Strong, K., Tack, F., Tian, Xin, Tiefengraber, M., Tirpitz, J.-L., Gent, J. van, Volkamer, R., Vrekoussis, M., Wang, Shanshan, Wang, Zhuoru, Wenig, Mark, Wittrock, F., Xie, P.H., Xu, Jin, Yela, M., Zhang, Chengxin, Zhao, Xiaoyi, Netherlands Space Office, European Space Agency, European Commission, Austrian Science Fund, University of Toronto, Canadian Space Agency, Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, Consejo Superior de Investigaciones Científicas (España), Ministerio de Economía y Competitividad (España), German Research Foundation, Centre National de la Recherche Scientifique (France), Centre National D'Etudes Spatiales (France), Russian Science Foundation, Russian Foundation for Basic Research, National Aeronautics and Space Administration (US), National Science Foundation (US), University of Bremen, NASA's Goddard Space Flight Center, Kreher, Karin, Roozendael, Michel van, Hendrick, Francois, Apituley, Arnoud, Dimitropoulou, Ermioni, Frieß, Udo, Richter, Andreas, Wagner, Thomas, Lampel, Johannes, Abuhassan, Nader, Ang, Li, Anguas, Mónica, Bais, Alkis, Benavent, Nuria, Bösch, Tim, Bognar, Kristof, Borovski, Alexander, Bruchkouski, Ilya, Cede, Alexander, Lok Chan, Ka, Donner, Sebastian, Drosoglou, Theano, Fayt, Caroline, Finkenzeller, Henning, García-Nieto, D., Gielen, Clio, Gómez-Martín, L., Hao, Nan, Henzing, Bas, Herman, Jay R., Hermans, Christian, Hoque, Syedul, Iri, Hitoshi, Jin, Junli, Johnsto, Paul, Khayyam But, Junaid, Khokhar, Fahim, Koenig, T.K., Kuhn, Jonas, Kumar, Vinod, Li, Cheng, Ma, Jianzhong, Merlaud, Alexis, Mishra, A.K., Müller, Moritz, Navarro-Comas, M., Ostendorf, M., Pazmin, Andrea, Peters, Enno, Pinardi, Gaia, Pinharanda, M., Piters, Ankie, Platt, Ulrich, Postylyakov, Oleg, Prados-Roman, C., Puentedura, Olga, Querel, Richard, Saiz-Lopez, A., Schönhardt, A., Schreier, S.F., Seyler, André, Sinha, V., Spinei, Elena, Strong, K., Tack, F., Tian, Xin, Tiefengraber, M., Tirpitz, J.-L., Gent, J. van, Volkamer, R., Vrekoussis, M., Wang, Shanshan, Wang, Zhuoru, Wenig, Mark, Wittrock, F., Xie, P.H., Xu, Jin, Yela, M., Zhang, Chengxin, and Zhao, Xiaoyi
Abstract: In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17¿d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97¿¿N, 4.93¿¿E). We report on the outcome of the formal semi-blind intercomparison exercise, which was held under the umbrella of the Network for the Detection of Atmospheric Composition Change (NDACC) and the European Space Agency (ESA). The three major goals of CINDI-2 were (1) to characterise and better understand the differences between a large number of multi-axis differential optical absorption spectroscopy (MAX-DOAS) and zenith-sky DOAS instruments and analysis methods, (2) to define a robust methodology for performance assessment of all participating instruments, and (3) to contribute to a harmonisation of the measurement settings and retrieval methods. This, in turn, creates the capability to produce consistent high-quality ground-based data sets, which are an essential requirement to generate reliable long-term measurement time series suitable for trend analysis and satellite data validation. The data products investigated during the semi-blind intercomparison are slant columns of nitrogen dioxide (NO2), the oxygen collision complex (O4) and ozone (O3) measured in the UV and visible wavelength region, formaldehyde (HCHO) in the UV spectral region, and NO2 in an additional (smaller) wavelength range in the visible region. The campaign design and implementation processes are discussed in detail including the measurement protocol, calibration procedures and slant column retrieval settings. Strong emphasis was put on the careful alignment and synchronisation of the measurement systems, resulting in a unique set of measurements made under highly comparable air mass conditions. The CINDI-2 data sets were investigated using a regression analysis of the slant columns measured by each instrument
Published: 2020

9. A feasibility study to use machine learning as an inversion algorithm for aerosol profile and property retrieval from multi-axis differential absorption spectroscopy measurements

Author: Electrical and Computer Engineering, Computer Science, Dong, Yun, Spinei, Elena, Karpatne, Anuj, Electrical and Computer Engineering, Computer Science, Dong, Yun, Spinei, Elena, and Karpatne, Anuj
Abstract: In this study, we explore a new approach based on machine learning (ML) for deriving aerosol extinction coefficient profiles, single-scattering albedo and asymmetry parameter at 360 nm from a single multi-axis differential optical absorption spectroscopy (MAX-DOAS) sky scan. Our method relies on a multi-output sequence-to-sequence model combining convolutional neural networks (CNNs) for feature extraction and long short-term memory networks (LSTMs) for profile prediction. The model was trained and evaluated using data simulated by Vector Linearized Discrete Ordinate Radiative Transfer (VLIDORT) v2.7, which contains 1 459 200 unique mappings. From the simulations, 75 % were randomly selected for training and the remaining 25 % for validation. The overall error of estimated aerosol properties (1) for total aerosol optical depth (AOD) is -1.4 +/- 10.1 %, (2) for the single-scattering albedo is 0.1 +/- 3.6 %, and (3) for the asymmetry factor is -0.1 +/- 2.1 %. The resulting model is capable of retrieving aerosol extinction coefficient profiles with degrading accuracy as a function of height. The uncertainty due to the randomness in ML training is also discussed.
Published: 2020

10. Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV–visible spectrometers during CINDI-2

Author: Electrical and Computer Engineering, Kreher, Karin, Van Roozendael, Michel, Hendrick, Francois, Apituley, Arnoud, Dimitropoulou, Ermioni, Friess, Udo, Richter, Andreas, Wagner, Thomas, Lampel, Johannes, Abuhassan, Nader, Ang, Li, Anguas, Monica, Bais, Alkis, Benavent, Nuria, Boesch, Tim, Bognar, Kristof, Borovski, Alexander, Bruchkouski, Ilya, Cede, Alexander, Chan, Ka Lok, Donner, Sebastian, Drosoglou, Theano, Fayt, Caroline, Finkenzeller, Henning, Garcia-Nieto, David, Gielen, Clio, Gomez-Martin, Laura, Hao, Nan, Henzing, Bas, Herman, Jay R., Hermans, Christian, Hoque, Syedul, Irie, Hitoshi, Jin, Junli, Johnston, Paul, Butt, Junaid Khayyam, Khokhar, Fahim, Koenig, Theodore K., Kuhn, Jonas, Kumar, Vinod, Liu, Cheng, Ma, Jianzhong, Merlaud, Alexis, Mishra, Abhishek K., Mueller, Moritz, Navarro-Comas, Monica, Ostendorf, Mareike, Pazmino, Andrea, Peters, Enno, Pinardi, Gaia, Pinharanda, Manuel, Piters, Ankie, Platt, Ulrich, Postylyakov, Oleg, Prados-Roman, Cristina, Puentedura, Olga, Querel, Richard, Saiz-Lopez, Alfonso, Schoenhardt, Anja, Schreier, Stefan F., Seyler, Andre, Sinha, Vinayak, Spinei, Elena, Strong, Kimberly, Tack, Frederik, Tian, Xin, Tiefengraber, Martin, Tirpitz, Jan-Lukas, van Gent, Jeron, Volkamer, Rainer, Vrekoussis, Mihalis, Wang, Shanshan, Wang, Zhuoru, Wenig, Mark, Wittrock, Folkard, Xie, Pinhua H., Xu, Jin, Yela, Margarita, Zhang, Chengxin, Zhao, Xiaoyi, Electrical and Computer Engineering, Kreher, Karin, Van Roozendael, Michel, Hendrick, Francois, Apituley, Arnoud, Dimitropoulou, Ermioni, Friess, Udo, Richter, Andreas, Wagner, Thomas, Lampel, Johannes, Abuhassan, Nader, Ang, Li, Anguas, Monica, Bais, Alkis, Benavent, Nuria, Boesch, Tim, Bognar, Kristof, Borovski, Alexander, Bruchkouski, Ilya, Cede, Alexander, Chan, Ka Lok, Donner, Sebastian, Drosoglou, Theano, Fayt, Caroline, Finkenzeller, Henning, Garcia-Nieto, David, Gielen, Clio, Gomez-Martin, Laura, Hao, Nan, Henzing, Bas, Herman, Jay R., Hermans, Christian, Hoque, Syedul, Irie, Hitoshi, Jin, Junli, Johnston, Paul, Butt, Junaid Khayyam, Khokhar, Fahim, Koenig, Theodore K., Kuhn, Jonas, Kumar, Vinod, Liu, Cheng, Ma, Jianzhong, Merlaud, Alexis, Mishra, Abhishek K., Mueller, Moritz, Navarro-Comas, Monica, Ostendorf, Mareike, Pazmino, Andrea, Peters, Enno, Pinardi, Gaia, Pinharanda, Manuel, Piters, Ankie, Platt, Ulrich, Postylyakov, Oleg, Prados-Roman, Cristina, Puentedura, Olga, Querel, Richard, Saiz-Lopez, Alfonso, Schoenhardt, Anja, Schreier, Stefan F., Seyler, Andre, Sinha, Vinayak, Spinei, Elena, Strong, Kimberly, Tack, Frederik, Tian, Xin, Tiefengraber, Martin, Tirpitz, Jan-Lukas, van Gent, Jeron, Volkamer, Rainer, Vrekoussis, Mihalis, Wang, Shanshan, Wang, Zhuoru, Wenig, Mark, Wittrock, Folkard, Xie, Pinhua H., Xu, Jin, Yela, Margarita, Zhang, Chengxin, and Zhao, Xiaoyi
Abstract: In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17 d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97 degrees N, 4.93 degrees E). We report on the outcome of the formal semi-blind intercomparison exercise, which was held under the umbrella of the Network for the Detection of Atmospheric Composition Change (NDACC) and the European Space Agency (ESA). The three major goals of CINDI-2 were (1) to characterise and better understand the differences between a large number of multi-axis differential optical absorption spectroscopy (MAX-DOAS) and zenith-sky DOAS instruments and analysis methods, (2) to define a robust methodology for performance assessment of all participating instruments, and (3) to contribute to a harmonisation of the measurement settings and retrieval methods. This, in turn, creates the capability to produce consistent high-quality ground-based data sets, which are an essential requirement to generate reliable long-term measurement time series suitable for trend analysis and satellite data validation. The data products investigated during the semi-blind intercomparison are slant columns of nitrogen dioxide (NO2), the oxygen collision complex (O-4) and ozone (O-3) measured in the UV and visible wavelength region, formaldehyde (HCHO) in the UV spectral region, and NO2 in an additional (smaller) wavelength range in the visible region. The campaign design and implementation processes are discussed in detail including the measurement protocol, calibration procedures and slant column retrieval settings. Strong emphasis was put on the careful alignment and synchronisation of the measurement systems, resulting in a unique set of measurements made under highly comparable air mass conditions. The CINDI-2 data sets were investigated using a regression analysis of the slant columns measured by
Published: 2020

11. Effect of polyoxymethylene (POM-H Delrin) off-gassing within the Pandora head sensor on direct-sun and multi-axis formaldehyde column measurements in 2016–2019

Author: Spinei, Elena, primary, Tiefengraber, Martin, additional, Müller, Moritz, additional, Gebetsberger, Manuel, additional, Cede, Alexander, additional, Valin, Luke, additional, Szykman, James, additional, Whitehill, Andrew, additional, Kotsakis, Alexander, additional, Santos, Fernando, additional, Abbuhasan, Nader, additional, Zhao, Xiaoyi, additional, Fioletov, Vitali, additional, Lee, Sum Chi, additional, and Swap, Robert, additional
Published: 2021
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12. Intercomparison of MAX-DOAS vertical profile retrieval algorithms: studies on field data from the CINDI-2 campaign

Author: Tirpitz, Jan-Lukas, primary, Frieß, Udo, additional, Hendrick, François, additional, Alberti, Carlos, additional, Allaart, Marc, additional, Apituley, Arnoud, additional, Bais, Alkis, additional, Beirle, Steffen, additional, Berkhout, Stijn, additional, Bognar, Kristof, additional, Bösch, Tim, additional, Bruchkouski, Ilya, additional, Cede, Alexander, additional, Chan, Ka Lok, additional, den Hoed, Mirjam, additional, Donner, Sebastian, additional, Drosoglou, Theano, additional, Fayt, Caroline, additional, Friedrich, Martina M., additional, Frumau, Arnoud, additional, Gast, Lou, additional, Gielen, Clio, additional, Gomez-Martín, Laura, additional, Hao, Nan, additional, Hensen, Arjan, additional, Henzing, Bas, additional, Hermans, Christian, additional, Jin, Junli, additional, Kreher, Karin, additional, Kuhn, Jonas, additional, Lampel, Johannes, additional, Li, Ang, additional, Liu, Cheng, additional, Liu, Haoran, additional, Ma, Jianzhong, additional, Merlaud, Alexis, additional, Peters, Enno, additional, Pinardi, Gaia, additional, Piters, Ankie, additional, Platt, Ulrich, additional, Puentedura, Olga, additional, Richter, Andreas, additional, Schmitt, Stefan, additional, Spinei, Elena, additional, Stein Zweers, Deborah, additional, Strong, Kimberly, additional, Swart, Daan, additional, Tack, Frederik, additional, Tiefengraber, Martin, additional, van der Hoff, René, additional, van Roozendael, Michel, additional, Vlemmix, Tim, additional, Vonk, Jan, additional, Wagner, Thomas, additional, Wang, Yang, additional, Wang, Zhuoru, additional, Wenig, Mark, additional, Wiegner, Matthias, additional, Wittrock, Folkard, additional, Xie, Pinhua, additional, Xing, Chengzhi, additional, Xu, Jin, additional, Yela, Margarita, additional, Zhang, Chengxin, additional, and Zhao, Xiaoyi, additional
Published: 2021
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13. A method for quantifying near range point source induced O3 titration events using Co-located Lidar and Pandora measurements

Author: Gronoff, Guillaume, Robinson, Joseph, Berkoff, Timothy, Swap, Robert, Farris, Betsy, Schroeder, Jeremy, Halliday, Hannah S., Knepp, Travis, Spinei, Elena, Carrion, William, Adcock, Edward E., Johns, Zachary, Allen, Danette, and Pippin, Margaret
Published: 2019
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14. Response to comments by Anonymous Referee 2

Author: Spinei, Elena, primary
Published: 2020
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15. Response to comments by Anonymous Referee 1

Author: Spinei, Elena, primary
Published: 2020
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16. A feasibility study to use machine learning as an inversion algorithm for aerosol profile and property retrieval from multi-axis differential absorption spectroscopy measurements

Author: Dong, Yun, primary, Spinei, Elena, additional, and Karpatne, Anuj, additional
Published: 2020
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17. Effect of Polyoxymethylene (POM-H Delrin) offgassing within Pandora head sensor on direct sun and multi-axis formaldehyde column measurements in 2016–2019

Author: Spinei, Elena, primary, Tiefengraber, Martin, additional, Müller, Moritz, additional, Gebetsberger, Manuel, additional, Cede, Alexander, additional, Valin, Luke, additional, Szykman, James, additional, Whitehill, Andrew, additional, Kotsakis, Alexander, additional, Santos, Fernando, additional, Abbuhasan, Nader, additional, Zhao, Xiaoyi, additional, Fioletov, Vitali, additional, Lee, Sum Chi, additional, and Swap, Robert, additional
Published: 2020
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18. Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV–visible spectrometers during CINDI-2

Author: Kreher, Karin, primary, Van Roozendael, Michel, additional, Hendrick, Francois, additional, Apituley, Arnoud, additional, Dimitropoulou, Ermioni, additional, Frieß, Udo, additional, Richter, Andreas, additional, Wagner, Thomas, additional, Lampel, Johannes, additional, Abuhassan, Nader, additional, Ang, Li, additional, Anguas, Monica, additional, Bais, Alkis, additional, Benavent, Nuria, additional, Bösch, Tim, additional, Bognar, Kristof, additional, Borovski, Alexander, additional, Bruchkouski, Ilya, additional, Cede, Alexander, additional, Chan, Ka Lok, additional, Donner, Sebastian, additional, Drosoglou, Theano, additional, Fayt, Caroline, additional, Finkenzeller, Henning, additional, Garcia-Nieto, David, additional, Gielen, Clio, additional, Gómez-Martín, Laura, additional, Hao, Nan, additional, Henzing, Bas, additional, Herman, Jay R., additional, Hermans, Christian, additional, Hoque, Syedul, additional, Irie, Hitoshi, additional, Jin, Junli, additional, Johnston, Paul, additional, Khayyam Butt, Junaid, additional, Khokhar, Fahim, additional, Koenig, Theodore K., additional, Kuhn, Jonas, additional, Kumar, Vinod, additional, Liu, Cheng, additional, Ma, Jianzhong, additional, Merlaud, Alexis, additional, Mishra, Abhishek K., additional, Müller, Moritz, additional, Navarro-Comas, Monica, additional, Ostendorf, Mareike, additional, Pazmino, Andrea, additional, Peters, Enno, additional, Pinardi, Gaia, additional, Pinharanda, Manuel, additional, Piters, Ankie, additional, Platt, Ulrich, additional, Postylyakov, Oleg, additional, Prados-Roman, Cristina, additional, Puentedura, Olga, additional, Querel, Richard, additional, Saiz-Lopez, Alfonso, additional, Schönhardt, Anja, additional, Schreier, Stefan F., additional, Seyler, André, additional, Sinha, Vinayak, additional, Spinei, Elena, additional, Strong, Kimberly, additional, Tack, Frederik, additional, Tian, Xin, additional, Tiefengraber, Martin, additional, Tirpitz, Jan-Lukas, additional, van Gent, Jeroen, additional, Volkamer, Rainer, additional, Vrekoussis, Mihalis, additional, Wang, Shanshan, additional, Wang, Zhuoru, additional, Wenig, Mark, additional, Wittrock, Folkard, additional, Xie, Pinhua H., additional, Xu, Jin, additional, Yela, Margarita, additional, Zhang, Chengxin, additional, and Zhao, Xiaoyi, additional
Published: 2020
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19. Title: Urban air pollution monitoring at micro-, local and meso- scales using Pandora instrument

Author: Spinei, Elena, primary, Geddes, Jeffrey, additional, Adams, Taylor, additional, Müller, Moritz, additional, and Gebetsberger, Manuel, additional
Published: 2020
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20. MAX-DOAS measurements of atmospheric rural and urban NO2 gradients during the TROLIX'19 campaign

Author: Kreher, Karin, primary, Spinei, Elena, additional, Piters, Ankie, additional, Apituley, Arnoud, additional, Bais, Alkis, additional, Doerner, Steffen, additional, Fayt, Caroline, additional, Friedrich, Martina, additional, Frumau, Arnoud, additional, Hendrick, Francois, additional, Hermans, Christian, additional, Karagkiozidis, Dimitris, additional, Querel, Richard, additional, Van Roozendael, Michel, additional, Vonk, Jan, additional, and Wagner, Thomas, additional
Published: 2020
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21. Intercomparison of MAX-DOAS vertical profile retrieval algorithms: studies on field data from the CINDI-2 campaign

Author: Tirpitz, Jan-Lukas, primary, Frieß, Udo, additional, Hendrick, François, additional, Alberti, Carlos, additional, Allaart, Marc, additional, Apituley, Arnoud, additional, Bais, Alkis, additional, Beirle, Steffen, additional, Berkhout, Stijn, additional, Bognar, Kristof, additional, Bösch, Tim, additional, Bruchkouski, Ilya, additional, Cede, Alexander, additional, Chan, Ka Lok, additional, den Hoed, Mirjam, additional, Donner, Sebastian, additional, Drosoglou, Theano, additional, Fayt, Caroline, additional, Friedrich, Martina M., additional, Frumau, Arnoud, additional, Gast, Lou, additional, Gielen, Clio, additional, Gomez-Martín, Laura, additional, Hao, Nan, additional, Hensen, Arjen, additional, Henzing, Bas, additional, Hermans, Christian, additional, Jin, Junli, additional, Kreher, Karin, additional, Kuhn, Jonas, additional, Lampel, Johannes, additional, Li, Ang, additional, Liu, Cheng, additional, Liu, Haoran, additional, Ma, Jianzhong, additional, Merlaud, Alexis, additional, Peters, Enno, additional, Pinardi, Gaia, additional, Piters, Ankie, additional, Platt, Ulrich, additional, Puentedura, Olga, additional, Richter, Andreas, additional, Schmitt, Stefan, additional, Spinei, Elena, additional, Stein Zweers, Deborah, additional, Strong, Kimberly, additional, Swart, Daan, additional, Tack, Frederick, additional, Tiefengraber, Martin, additional, van der Hoff, René, additional, van Roozendael, Michel, additional, Vlemmix, Tim, additional, Vonk, Jan, additional, Wagner, Thomas, additional, Wang, Yang, additional, Wang, Zhuoru, additional, Wenig, Mark, additional, Wiegner, Matthias, additional, Wittrock, Folkard, additional, Xie, Pinhua, additional, Xing, Chengzhi, additional, Xu, Jin, additional, Yela, Margarita, additional, Zhang, Chengxin, additional, and Zhao, Xiaoyi, additional
Published: 2020
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22. Supplementary material to "Intercomparison of MAX-DOAS vertical profile retrieval algorithms: studies on field data from the CINDI-2 campaign"

Author: Tirpitz, Jan-Lukas, primary, Frieß, Udo, additional, Hendrick, François, additional, Alberti, Carlos, additional, Allaart, Marc, additional, Apituley, Arnoud, additional, Bais, Alkis, additional, Beirle, Steffen, additional, Berkhout, Stijn, additional, Bognar, Kristof, additional, Bösch, Tim, additional, Bruchkouski, Ilya, additional, Cede, Alexander, additional, Chan, Ka Lok, additional, den Hoed, Mirjam, additional, Donner, Sebastian, additional, Drosoglou, Theano, additional, Fayt, Caroline, additional, Friedrich, Martina M., additional, Frumau, Arnoud, additional, Gast, Lou, additional, Gielen, Clio, additional, Gomez-Martín, Laura, additional, Hao, Nan, additional, Hensen, Arjen, additional, Henzing, Bas, additional, Hermans, Christian, additional, Jin, Junli, additional, Kreher, Karin, additional, Kuhn, Jonas, additional, Lampel, Johannes, additional, Li, Ang, additional, Liu, Cheng, additional, Liu, Haoran, additional, Ma, Jianzhong, additional, Merlaud, Alexis, additional, Peters, Enno, additional, Pinardi, Gaia, additional, Piters, Ankie, additional, Platt, Ulrich, additional, Puentedura, Olga, additional, Richter, Andreas, additional, Schmitt, Stefan, additional, Spinei, Elena, additional, Stein Zweers, Deborah, additional, Strong, Kimberly, additional, Swart, Daan, additional, Tack, Frederick, additional, Tiefengraber, Martin, additional, van der Hoff, René, additional, van Roozendael, Michel, additional, Vlemmix, Tim, additional, Vonk, Jan, additional, Wagner, Thomas, additional, Wang, Yang, additional, Wang, Zhuoru, additional, Wenig, Mark, additional, Wiegner, Matthias, additional, Wittrock, Folkard, additional, Xie, Pinhua, additional, Xing, Chengzhi, additional, Xu, Jin, additional, Yela, Margarita, additional, Zhang, Chengxin, additional, and Zhao, Xiaoyi, additional
Published: 2020
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23. Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV-Visible spectrometers during the CINDI-2 campaign

Author: Kreher, Karin, Roozendael, Michel, Hendrick, Francois, Apituley, Arnoud, Dimitropoulou, Ermioni, Frieß, Udo, Richter, Andreas, Wagner, Thomas, Abuhassan, Nader, Ang, Li, Anguas, Monica, Bais, Alkis, Benavent, Nuria, Bösch, Tim, Bognar, Kristof, Borovski, Alexander, Bruchkouski, Ilya, Cede, Alexander, Chan, Ka L., Donner, Sebastian, Drosoglou, Theano, Fayt, Caroline, Finkenzeller, Henning, Garcia-Nieto, David, Gielen, Clio, Gómez-Martín, Laura, Hao, Nan, Herman, Jay R., Hermans, Christian, Hoque, Syedul, Irie, Hitoshi, Jin, Junli, Johnston, Paul, Khayyam Butt, Junaid, Khokhar, Fahim, Koenig, Theodore K., Kuhn, Jonas, Kumar, Vinod, Lampel, Johannes, Liu, Cheng, Ma, Jianzhong, Merlaud, Alexis, Mishra, Abhishek K., Müller, Moritz, Navarro-Comas, Monica, Ostendorf, Mareike, Pazmino, Andrea, Peters, Enno, Pinardi, Gaia, Pinharanda, Manuel, Piters, Ankie, Platt, Ulrich, Postylyakov, Oleg, Prados-Roman, Cristina, Puentedura, Olga, Querel, Richard, Saiz-Lopez, Alfonso, Schönhardt, Anja, Schreier, Stefan F., Seyler, Andre, Sinha, Vinayak, Spinei, Elena, Strong, Kimberly, Tack, Frederik, Tian, Xin, Tiefengraber, Martin, Tirpitz, Jan-Lukas, Gent, Jeron, Volkamer, Rainer, Vrekoussis, Mihalis, Wang, Shanshan, Wang, Zhuoru, Wenig, Mark, Wittrock, Folkard, Xie, Pinhua H., Xu, Jin, Yela, Margarita, Zhang, Chengxin, and Zhao, Xiaoyi
Abstract: In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17 days during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, The Netherlands (51.97° N, 4.93° E). We report on the outcome of the formal semi-blind intercomparison exercise, which was held under the umbrella of the Network for the Detection of Atmospheric Composition Change (NDACC) and the European Space Agency (ESA). The three major goals of CINDI-2 were to characterise and better understand the differences between a large number of Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) and zenith-sky DOAS instruments and analysis methods, to discuss the performance of the various types of instruments and to contribute to a harmonisation of the measurement settings and retrieval methods. This, in turn, creates the capability to produce consistent high-quality ground-based data sets, which are an essential requirement to generate reliable long-term measurement time series suitable for trend analysis and satellite data validation. The data products investigated during the semi-blind intercomparison are slant columns of nitrogen dioxide (NO2), the oxygen dimer (O4) and ozone (O3) measured in the UV and visible wavelength region, formaldehyde (HCHO) in the UV spectral region and NO2 in an additional (smaller) wavelength range in the visible. The campaign design and implementation processes are discussed in detail including the measurement protocol, calibration procedures and slant column retrieval settings. Strong emphasis was put on the careful alignment and synchronisation of the measurement systems, resulting in an unprecedented set of measurements made under highly comparable air mass conditions. The CINDI-2 data sets were investigated using a regression analysis of the slant columns measured by each instrument and for each of the target data products. The slope and intercept of the regression analysis respectively quantify the mean systematic bias and offset of the individual data sets against the reference, and the RMS error provides an estimate of the measurement noise or dispersion. These three criteria are examined and for each of the parameters and each of the data products, performance thresholds are set and applied to all the measurements. The approach presented here has been developed based on heritage from previous intercomparison exercises. It introduces a quantitative assessment of the measurement performance of all the participating instruments for the MAX-DOAS and zenith-sky DOAS techniques.
Published: 2019

24. NO₂ and HCHO measurements in Korea from 2012 to 2016 from Pandora spectrometer instruments compared with OMI retrievals and with aircraft measurements during the KORUS-AQ campaign

Author: Herman, Jay, Spinei, Elena, Fried, Alan, Kim, Jhoon, Kim, Jae, Kim, Woogyung, Cede, Alexander, Abuhassan, Nader, and Segal-Rozenhaimer, Michal
Abstract: Nine Pandora spectrometer instruments (PSI) were installed at eight sites in South Korea as part of the KORUS-AQ (Korea U.S.-Air Quality) field study integrating information from ground, aircraft, and satellite measurements for validation of remote sensing air-quality studies. The PSI made direct-sun measurements of total vertical column NO₂, C(NO₂), with high precision (0.05 DU, where 1 DU = 2.69 × 1016 molecules cm−2 ) and accuracy (0.1 DU) that were retrieved using spectral fitting techniques. Retrieval of formaldehyde C(HCHO) total column amounts were also obtained at five sites using the recently improved PSI optics. The C(HCHO) retrievals have high precision, but possibly lower accuracy than for NO₂ because of uncertainty about the optimum spectral window for all ground-based and satellite instruments. PSI direct-sun retrieved values for C(NO₂) and C(HCHO) are always significantly larger than OMI (AURA satellite Ozone Monitoring Instrument) retrieved C(NO₂) and C(HCHO) for the OMI overpass local times (KST = 13.5±0.5 h). In urban areas, PSI C(NO₂) 30- day running averages are at least a factor of two larger than OMI averages. Similar differences are seen for C(HCHO) in Seoul and nearby surrounding areas. Late afternoon values of C(HCHO) measured by PSI are even larger, implying that OMI early afternoon measurements underestimate the effect of poor air quality on human health. The primary cause of OMI underestimates is the large OMI field of view (FOV) that includes regions containing low values of pollutants. In relatively clean areas, PSI and OMI are more closely in agreement. C(HCHO) amounts were obtained for five sites, Yonsei University in Seoul, Olympic Park, Taehwa Mountain, Amnyeondo, and Yeoju. Of these, the largest amounts of C(HCHO) were observed at Olympic Park and Taehwa Mountain, surrounded by significant amounts of vegetation. Comparisons of PSI C(HCHO) results were made with the Compact Atmospheric Multispecies Spectrometer CAMS during overflights on the DC-8 aircraft for Taehwa Mountain and Olympic Park. In all cases, PSI measured substantially more C(HCHO) than obtained from integrating the CAMS altitude profiles. PSI C(HCHO) at Yonsei University in Seoul frequently reached 0.6 DU and occasionally exceeded 1.5 DU. The semi-rural site, Taehwa Mountain, frequently reached 0.9 DU and occasionally exceeded 1.5 DU. Even at the cleanest site, Amnyeondo, C(HCHO) occasionally exceeded 1 DU.
Published: 2018
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25. Machine learning as an inversion algorithm for aerosol profile and property retrieval from multi-axis differential absorption spectroscopy measurements: a feasibility study

Author: Dong, Yun, primary, Spinei, Elena, additional, and Karpatne, Anuj, additional
Published: 2019
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26. Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV-Visible spectrometers during the CINDI-2 campaign

Author: Kreher, Karin, primary, Van Roozendael, Michel, additional, Hendrick, Francois, additional, Apituley, Arnoud, additional, Dimitropoulou, Ermioni, additional, Frieß, Udo, additional, Richter, Andreas, additional, Wagner, Thomas, additional, Abuhassan, Nader, additional, Ang, Li, additional, Anguas, Monica, additional, Bais, Alkis, additional, Benavent, Nuria, additional, Bösch, Tim, additional, Bognar, Kristof, additional, Borovski, Alexander, additional, Bruchkouski, Ilya, additional, Cede, Alexander, additional, Chan, Ka L., additional, Donner, Sebastian, additional, Drosoglou, Theano, additional, Fayt, Caroline, additional, Finkenzeller, Henning, additional, Garcia-Nieto, David, additional, Gielen, Clio, additional, Gómez-Martín, Laura, additional, Hao, Nan, additional, Herman, Jay R., additional, Hermans, Christian, additional, Hoque, Syedul, additional, Irie, Hitoshi, additional, Jin, Junli, additional, Johnston, Paul, additional, Khayyam Butt, Junaid, additional, Khokhar, Fahim, additional, Koenig, Theodore K., additional, Kuhn, Jonas, additional, Kumar, Vinod, additional, Lampel, Johannes, additional, Liu, Cheng, additional, Ma, Jianzhong, additional, Merlaud, Alexis, additional, Mishra, Abhishek K., additional, Müller, Moritz, additional, Navarro-Comas, Monica, additional, Ostendorf, Mareike, additional, Pazmino, Andrea, additional, Peters, Enno, additional, Pinardi, Gaia, additional, Pinharanda, Manuel, additional, Piters, Ankie, additional, Platt, Ulrich, additional, Postylyakov, Oleg, additional, Prados-Roman, Cristina, additional, Puentedura, Olga, additional, Querel, Richard, additional, Saiz-Lopez, Alfonso, additional, Schönhardt, Anja, additional, Schreier, Stefan F., additional, Seyler, Andre, additional, Sinha, Vinayak, additional, Spinei, Elena, additional, Strong, Kimberly, additional, Tack, Frederik, additional, Tian, Xin, additional, Tiefengraber, Martin, additional, Tirpitz, Jan-Lukas, additional, van Gent, Jeron, additional, Volkamer, Rainer, additional, Vrekoussis, Mihalis, additional, Wang, Shanshan, additional, Wang, Zhuoru, additional, Wenig, Mark, additional, Wittrock, Folkard, additional, Xie, Pinhua H., additional, Xu, Jin, additional, Yela, Margarita, additional, Zhang, Chengxin, additional, and Zhao, Xiaoyi, additional
Published: 2019
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27. Supplementary material to "Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV-Visible spectrometers during the CINDI-2 campaign"

Author: Kreher, Karin, primary, Van Roozendael, Michel, additional, Hendrick, Francois, additional, Apituley, Arnoud, additional, Dimitropoulou, Ermioni, additional, Frieß, Udo, additional, Richter, Andreas, additional, Wagner, Thomas, additional, Abuhassan, Nader, additional, Ang, Li, additional, Anguas, Monica, additional, Bais, Alkis, additional, Benavent, Nuria, additional, Bösch, Tim, additional, Bognar, Kristof, additional, Borovski, Alexander, additional, Bruchkouski, Ilya, additional, Cede, Alexander, additional, Chan, Ka L., additional, Donner, Sebastian, additional, Drosoglou, Theano, additional, Fayt, Caroline, additional, Finkenzeller, Henning, additional, Garcia-Nieto, David, additional, Gielen, Clio, additional, Gómez-Martín, Laura, additional, Hao, Nan, additional, Herman, Jay R., additional, Hermans, Christian, additional, Hoque, Syedul, additional, Irie, Hitoshi, additional, Jin, Junli, additional, Johnston, Paul, additional, Khayyam Butt, Junaid, additional, Khokhar, Fahim, additional, Koenig, Theodore K., additional, Kuhn, Jonas, additional, Kumar, Vinod, additional, Lampel, Johannes, additional, Liu, Cheng, additional, Ma, Jianzhong, additional, Merlaud, Alexis, additional, Mishra, Abhishek K., additional, Müller, Moritz, additional, Navarro-Comas, Monica, additional, Ostendorf, Mareike, additional, Pazmino, Andrea, additional, Peters, Enno, additional, Pinardi, Gaia, additional, Pinharanda, Manuel, additional, Piters, Ankie, additional, Platt, Ulrich, additional, Postylyakov, Oleg, additional, Prados-Roman, Cristina, additional, Puentedura, Olga, additional, Querel, Richard, additional, Saiz-Lopez, Alfonso, additional, Schönhardt, Anja, additional, Schreier, Stefan F., additional, Seyler, Andre, additional, Sinha, Vinayak, additional, Spinei, Elena, additional, Strong, Kimberly, additional, Tack, Frederik, additional, Tian, Xin, additional, Tiefengraber, Martin, additional, Tirpitz, Jan-Lukas, additional, van Gent, Jeron, additional, Volkamer, Rainer, additional, Vrekoussis, Mihalis, additional, Wang, Shanshan, additional, Wang, Zhuoru, additional, Wenig, Mark, additional, Wittrock, Folkard, additional, Xie, Pinhua H., additional, Xu, Jin, additional, Yela, Margarita, additional, Zhang, Chengxin, additional, and Zhao, Xiaoyi, additional
Published: 2019
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28. Intercomparison of MAX-DOAS vertical profile retrieval algorithms: studies using synthetic data

Author: Frieß, Udo, primary, Beirle, Steffen, additional, Alvarado Bonilla, Leonardo, additional, Bösch, Tim, additional, Friedrich, Martina M., additional, Hendrick, François, additional, Piters, Ankie, additional, Richter, Andreas, additional, van Roozendael, Michel, additional, Rozanov, Vladimir V., additional, Spinei, Elena, additional, Tirpitz, Jan-Lukas, additional, Vlemmix, Tim, additional, Wagner, Thomas, additional, and Wang, Yang, additional
Published: 2019
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29. Intercomparison of MAX-DOAS Vertical Profile Retrieval Algorithms: Studies using Synthetic Data

Author: Frieß, Udo, primary, Beirle, Steffen, additional, Alvarado Bonilla, Leonardo, additional, Bösch, Tim, additional, Friedrich, Martina M., additional, Hendrick, Francois, additional, Piters, Ankie, additional, Richter, Andreas, additional, van Roozendael, Michel, additional, Rozanov, Vladimir V., additional, Spinei, Elena, additional, Tirpitz, Jan-Lukas, additional, Vlemmix, Tim, additional, Wagner, Thomas, additional, and Wang, Yang, additional
Published: 2018
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30. Supplementary material to "Intercomparison of MAX-DOAS Vertical Profile Retrieval Algorithms: Studies using Synthetic Data"

Author: Frieß, Udo, primary, Beirle, Steffen, additional, Alvarado Bonilla, Leonardo, additional, Bösch, Tim, additional, Friedrich, Martina M., additional, Hendrick, Francois, additional, Piters, Ankie, additional, Richter, Andreas, additional, van Roozendael, Michel, additional, Rozanov, Vladimir V., additional, Spinei, Elena, additional, Tirpitz, Jan-Lukas, additional, Vlemmix, Tim, additional, Wagner, Thomas, additional, and Wang, Yang, additional
Published: 2018
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31. Effect of Polyoxymethylene (POM-H Delrin) offgassing within Pandora head sensor on direct sun and multi-axis formaldehyde column measurements in 2016-2019.

Author: Spinei, Elena, Tiefengraber, Martin, Müller, Moritz, Gebetsberger, Manuel, Cede, Alexander, Valin, Luke, Szykman, James, Whitehill, Andrew, Kotsakis, Alexander, Santos, Fernando, Abbuhasan, Nader, Xiaoyi Zhao, Fioletov, Vitali, Sum Chi Lee, and Swap, Robert
Subjects: *FORMALDEHYDE, *POLYOXYMETHYLENE, *ZENITH distance, *DETECTORS, *EXPONENTIAL functions, *SOLAR temperature
Abstract: Analysis of formaldehyde measurements by the Pandora spectrometer systems between 2016 and 2019 suggested that there was a temperature dependent process inside Pandora head sensor that emitted formaldehyde. Some parts in the head sensor were manufactured from thermal plastic polyoxymethylene homopolimer (E.I. Du Pont de Nemour & Co., USA: POM-H Delrin®) and were responsible for formaldehyde production. Laboratory analysis of the four Pandora head sensors showed that internal formaldehyde production had exponential temperature dependence with a damping coefficient of 0.0911 ± 0.0024 °C-1 and the exponential function amplitude ranging from 0.0041 DU to 0.049 DU. No apparent dependency on the head sensor age and heating/cooling rates was detected. The total amount of formaldehyde internally generated by the POM-H components and contributing to the direct sun measurements were estimated based on the head sensor temperature and solar zenith angle of the measurements. Measurements in winter, during "cold" days in general and at high solar zenith angles (> 75 °) were minimally impacted. Measurements during hot days and small solar zenith angles had up to 1 DU contribution from POM-H parts. Multi-axis differential slant column densities were minimally impacted (< 0.01 DU) due to the reference spectrum collected within a short time period with a small difference in head sensor temperature. Three new POM-free Pandora head sensors (manufactured in summer 2019) were evaluated for temperature dependent attenuation across the entire spectral range (300 to 530 nm). No formaldehyde or any other absorption above the instrumental noise was observed across the entire spectral range. [ABSTRACT FROM AUTHOR]
Published: 2020
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32. Nitrogen dioxide and formaldehyde measurements from the GEOstationary Coastal and Air Pollution Events (GEO-CAPE) Airborne Simulator over Houston, Texas

Author: Nowlan, Caroline R., primary, Liu, Xiong, additional, Janz, Scott J., additional, Kowalewski, Matthew G., additional, Chance, Kelly, additional, Follette-Cook, Melanie B., additional, Fried, Alan, additional, González Abad, Gonzalo, additional, Herman, Jay R., additional, Judd, Laura M., additional, Kwon, Hyeong-Ahn, additional, Loughner, Christopher P., additional, Pickering, Kenneth E., additional, Richter, Dirk, additional, Spinei, Elena, additional, Walega, James, additional, Weibring, Petter, additional, and Weinheimer, Andrew J., additional
Published: 2018
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33. The first evaluation of formaldehyde column observations by improved Pandora spectrometers during the KORUS-AQ field study

Author: Spinei, Elena, primary, Whitehill, Andrew, additional, Fried, Alan, additional, Tiefengraber, Martin, additional, Knepp, Travis N., additional, Herndon, Scott, additional, Herman, Jay R., additional, Müller, Moritz, additional, Abuhassan, Nader, additional, Cede, Alexander, additional, Richter, Dirk, additional, Walega, James, additional, Crawford, James, additional, Szykman, James, additional, Valin, Lukas, additional, Williams, David J., additional, Long, Russell, additional, Swap, Robert J., additional, Lee, Youngjae, additional, Nowak, Nabil, additional, and Poche, Brett, additional
Published: 2018
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34. NO2 and HCHO measurements in Korea from 2012 to 2016 from Pandora spectrometer instruments compared with OMI retrievals and with aircraft measurements during the KORUS-AQ campaign

Author: Herman, Jay, primary, Spinei, Elena, additional, Fried, Alan, additional, Kim, Jhoon, additional, Kim, Jae, additional, Kim, Woogyung, additional, Cede, Alexander, additional, Abuhassan, Nader, additional, and Segal-Rozenhaimer, Michal, additional
Published: 2018
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35. Response to Reviewer 1 comments

Author: Spinei, Elena, primary
Published: 2018
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36. responses to reviewer 3 comments

Author: Spinei, Elena, primary
Published: 2018
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37. The First Evaluation of Formaldehyde Column Observations by Pandora Spectrometers during the KORUS-AQ Field Study

Author: Spinei, Elena, primary, Whitehill, Andrew, additional, Fried, Alan, additional, Tiefengraber, Martin, additional, Knepp, Travis N., additional, Herndon, Scott, additional, Herman, Jay R., additional, Müller, Moritz, additional, Abuhassan, Nader, additional, Cede, Alexander, additional, Weibring, Petter, additional, Richter, Dirk, additional, Walega, James, additional, Crawford, James, additional, Szykman, James, additional, Valin, Lukas, additional, Williams, David J., additional, Long, Russell, additional, Swap, Robert J., additional, Lee, Youngjae, additional, Nowak, Nabil, additional, and Poche, Brett, additional
Published: 2018
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38. Comparisons of spectral aerosol absorption in Seoul, South Korea

Author: Mok, Jungbin, primary, Krotkov, Nickolay A., additional, Torres, Omar, additional, Jethva, Hiren, additional, Li, Zhanqing, additional, Kim, Jhoon, additional, Koo, Ja-Ho, additional, Go, Sujung, additional, Irie, Hitoshi, additional, Labow, Gordon, additional, Eck, Thomas F., additional, Holben, Brent N., additional, Herman, Jay, additional, Loughman, Robert P., additional, Spinei, Elena, additional, Lee, Seoung Soo, additional, Khatri, Pradeep, additional, and Campanelli, Monica, additional
Published: 2017
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39. Machine learning as an inversion algorithm for aerosol profile and property retrieval from multi-axis differential absorption spectroscopy measurements: a feasibility study.

Author: Yun Dong, Spinei, Elena, and Karpatne, Anuj
Subjects: *ARTIFICIAL neural networks, *AEROSOLS, *FEASIBILITY studies, *SHORT-term memory, *FEATURE extraction
Abstract: In this study, we explore a new approach based on machine learning (ML) for deriving aerosol extinction coefficient profiles, single scattering albedo and asymmetry parameter at 360 nm from a single MAX-DOAS sky scan. Our method relies on a multi-output sequence-to-sequence model combining Convolutional Neural Networks (CNN) for feature extraction and Long Short-Term Memory networks (LSTM) for profile prediction. The model was trained and evaluated using data simulated by VLIDORT v2.7, which contains 1 459 200 unique mappings. 75 % randomly selected simulations were used for training and the remaining 25 % for validation. The overall error of estimated aerosol properties for (1) total AOD is −1.4 ± 10.1 %, (2) for single scattering albedo is 0.1 ± 3.6 %; and (3) asymmetry factor is −0.1 ± 2.1 %. The resulting model is capable of retrieving aerosol extinction coefficient profiles with degrading accuracy as a function of height. The uncertainty due to the randomness in ML training is also discussed. [ABSTRACT FROM AUTHOR]
Published: 2019
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40. Intercomparison of MAX-DOAS Vertical Profile Retrieval Algorithms: Studies using Synthetic Data.

Author: Frieß, Udo, Beirle, Steffen, Bonilla, Leonardo Alvarado, Bösch, Tim, Friedrich, Martina M., Hendrick, Francois, Piters, Ankie, Richter, Andreas, van Roozendael, Michel, Rozanov, Vladimir V., Spinei, Elena, Tirpitz, Jan-Lukas, Vlemmix, Tim, Wagner, Thomas, and Yang Wang
Subjects: TRACE gases, ATMOSPHERIC aerosols
Abstract: Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a widely used measurement technique for the detection of a variety of atmospheric trace gases. Using inverse modelling, the observation of trace gas column densities along different lines of sight enables the retrieval of aerosol and trace gas vertical profiles in the atmospheric boundary layer using appropriate retrieval algorithms. In this study, the ability of eight profile retrieval algorithms to reconstruct vertical profiles is assessed on the basis of synthetic measurements. Five of the algorithms are based on the optimal estimation method, two on parametrised approaches, and one using an analytical approach without involving any radiative transfer modelling. The synthetic measurements consist of the median of simulated slant column densities of O4 at 360nm and 477nm, as well as of HCHO at 343nm and NO2 at 477nm, from seven datasets simulated by five different radiative transfer models. Simulations are performed for a combination of 10 trace gas and 11 aerosol profiles, as well as 11 elevation angles, 3 solar 10 zenith and 3 relative azimuth angles. Overall, the results from the different algorithms show moderate to good performance for the retrieval of vertical profiles, surface concentrations and total columns. Except for some outliers, the root mean squares difference between true and retrieved state ranges between (0:05-0:1) km1 for aerosol extinction, and (2:5-5:0) × 1010molec/cm3 for HCHO and NO2 concentrations. [ABSTRACT FROM AUTHOR]
Published: 2018
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41. NO2 and HCHO measurements in Korea from 2012 to 2016 from Pandora spectrometer instruments compared with OMI retrievals and with aircraft measurements during the KORUS-AQ campaign.

Author: Herman, Jay, Spinei, Elena, Fried, Alan, Kim, Jhoon, Kim, Jae, Kim, Woogyung, Cede, Alexander, Abuhassan, Nader, and Segal-Rozenhaimer, Michal
Subjects: *NITROGEN dioxide, *FORMALDEHYDE, *SPECTROMETERS, *AIR quality, *POLLUTANTS
Abstract: Nine Pandora spectrometer instruments (PSI) were installed at eight sites in South Korea as part of the KORUS-AQ (Korea U.S.-Air Quality) field study integrating information from ground, aircraft, and satellite measurements for validation of remote sensing air-quality studies. The PSI made direct-sun measurements of total vertical column NO2, C.NO2), with high precision (0.05 DU, where 1DUD 2:69×1016 molecules cm-2) and accuracy (0.1 DU) that were retrieved using spectral fitting techniques. Retrieval of formaldehyde C(HCHO) total column amounts were also obtained at five sites using the recently improved PSI optics. The C(HCHO) retrievals have high precision, but possibly lower accuracy than for NO2 because of uncertainty about the optimum spectral window for all ground-based and satellite instruments. PSI direct-sun retrieved values for C(NO2) and C(HCHO) are always significantly larger than OMI (AURA satellite Ozone Monitoring Instrument) retrieved C(NO2) and C(HCHO) for the OMI overpass local times (KST D 13:5±0:5 h). In urban areas, PSI C(NO2) 30- day running averages are at least a factor of two larger than OMI averages. Similar differences are seen for C(HCHO) in Seoul and nearby surrounding areas. Late afternoon values of C(HCHO) measured by PSI are even larger, implying that OMI early afternoon measurements underestimate the effect of poor air quality on human health. The primary cause of OMI underestimates is the large OMI field of view (FOV) that includes regions containing low values of pollutants. In relatively clean areas, PSI and OMI are more closely in agreement. C(HCHO) amounts were obtained for five sites, Yonsei University in Seoul, Olympic Park, Taehwa Mountain, Amnyeondo, and Yeoju. Of these, the largest amounts of C(HCHO) were observed at Olympic Park and Taehwa Mountain, surrounded by significant amounts of vegetation. Comparisons of PSI C(HCHO) results were made with the Compact Atmospheric Multispecies Spectrometer CAMS during overflights on the DC-8 aircraft for Taehwa Mountain and Olympic Park. In all cases, PSI measured substantially more C(HCHO) than obtained from integrating the CAMS altitude profiles. PSI C(HCHO) at Yonsei University in Seoul frequently reached 0.6DU and occasionally exceeded 1.5 DU. The semi-rural site, Taehwa Mountain, frequently reached 0.9DU and occasionally exceeded 1.5 DU. Even at the cleanest site, Amnyeondo, C(HCHO) occasionally exceeded 1 DU. [ABSTRACT FROM AUTHOR]
Published: 2018
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42. The First Evaluation of Formaldehyde Column Observations by Pandora Spectrometers during the KORUS-AQ Field Study.

Author: Spinei, Elena, Whitehill, Andrew, Fried, Alan, Tiefengraber, Martin, Knepp, Travis N., Herndon, Scott, Herman, Jay R., Müller, Moritz, Abuhassan, Nader, Cede, Alexander, Weibring, Petter, Richter, Dirk, Walega, James, Crawford, James, Szykman, James, Valin, Lukas, Williams, David J., Long, Russell, Swap, Robert J., and Youngjae Lee
Subjects: *FORMALDEHYDE, *SPECTROMETERS, *TROPOSPHERE
Abstract: The KORUS-AQ field study conducted during May-June 2016 offered the first opportunity to evaluate direct-sun observations of formaldehyde (HCHO) total column densities with improved Pandora spectrometer instruments. The measurements highlighted in this work were conducted both in the Seoul megacity area at the Olympic Park site (latitude: 37.5232° N, longitude: 127.1260° E, 26 m a.s.l.) and at a nearby rural site downwind of the city at the Mount Taehwa Research Forest site (latitude: 37.3123° N, longitude: 127.3106° E, 160 m a.s.l.). Evaluation of these measurements was made possible by concurrent ground-based in situ observations of HCHO at both sites as well as overflight by the NASA DC-8 research aircraft. The flights provided in situ measurements of HCHO to characterize its vertical distribution in the lower troposphere (0-5 km). Diurnal variation in HCHO total column densities followed the same pattern at both sites, with the minimum daily values typically observed between 6:00-7:00 local time, gradually increasing to a maximum between 13:00 and 17:00 before decreasing into the evening. Pandora vertical column densities were compared with those derived from the DC-8 HCHO in-situ measured profiles augmented with in-situ surface concentrations below the lowest altitude of the DC-8 in proximity to the ground sites. A comparison between 49 column densities measured by Pandora versus aircraft integrated in-situ data showed that Pandora values were larger by 16 % (intercept = 0.22 DU, R² = 0.68). Pandora HCHO columns were also compared with columns calculated from the surface in-situ measurements over Olympic Park by assuming a well-mixed lower atmosphere up to a ceilometer measured mixed-layer height (MLH) and various assumptions about the small residual HCHO amounts in the free troposphere up to the tropopause. The best comparison (slope = 1.03 ± 0.03, intercept = 0.29 ± 0.02 DU and R² of 0.78 ± 0.02) was achieved assuming equal mixing within ceilometer measured MLH combined with an exponential profile shape. These results suggest that diurnal changes in HCHO surface concentrations can be reasonably estimated from the Pandora total column and information on the mixed-layer height. More work is needed to understand the bias in the intercept and the slope relative to columns derived from the in-situ aircraft and surface measurements. [ABSTRACT FROM AUTHOR]
Published: 2018
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43. Comparisons of spectral aerosol absorption in Seoul, South Korea.

Author: Jungbin Mok, Krotkov, Nickolay A., Torres, Omar, Jethva, Hiren, Zhanqing Li, Jhoon Kim, Ja-Ho Koo, Sujung Go, Hitoshi Irie, Labow, Gordon, Eck, Thomas F., Holben, Brent N., Herman, Jay, Loughman, Robert P., Spinei, Elena, Seoung Soo Lee, Khatri, Pradeep, and Campanelli, Monica
Subjects: ATMOSPHERIC aerosols, AIR pollution monitoring, SINGLE scattering (Optics)
Abstract: Quantifying the aerosol absorption at ultraviolet (UV) wavelengths is important for monitoring air pollution using current (e.g., Aura/OMI) and future (e.g., TROPOMI, TEMPO, GEMS, and Sentinel-4) satellite measurements. Measurements of column atmospheric aerosol absorption (i.e., column effective imaginary refractive index (k), single scattering albedo (SSA), and aerosol absorption optical depth (AAOD)) are performed on the ground by the NASA AERONET in the visible (VIS) and near-infrared (NIR) wavelengths and in the UV-VIS-NIR by the SKYNET networks. Previous comparison studies have focused on visible and NIR wavelengths due to the lack of co-incident measurements of aerosol and gaseous absorption properties in the UV. This study compares the SKYNET-retrieved SSA in the UV with the SSA derived from a combination of AERONET, MFRSR, and Pandora (AMP) retrievals in Seoul, South Korea in spring and summer of 2016. The results show that the spectrally invariant surface albedo assumed in the SKYNET SSA retrievals leads to underestimated SSA compared to AMP values at near UV wavelengths. Re-processed SKYNET inversions using spectrally varying surface albedo, consistent with the AERONET retrieval improves agreement with AMP SSA. The combined AMP inversions allow for separating aerosol and gaseous (NO2 and O3) absorption and provides aerosol retrievals from the shortest UVB (305 nm) through visible to NIR wavelengths (870 nm). [ABSTRACT FROM AUTHOR]
Published: 2017
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44. Direct Sun measurements of NO2 column abundances from Table Mountain, California: Intercomparison of low‐ and high‐resolution spectrometers

Author: Wang, Shuhui, primary, Pongetti, Thomas J., additional, Sander, Stanley P., additional, Spinei, Elena, additional, Mount, George H., additional, Cede, Alexander, additional, and Herman, Jay, additional
Published: 2010
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45. Validation of ozone monitoring instrument SO2 measurements in the Okmok volcanic cloud over Pullman, WA, July 2008

Author: Spinei, Elena, primary, Carn, Simon A., additional, Krotkov, Nickolay A., additional, Mount, George H., additional, Yang, Kai, additional, and Krueger, Arlin, additional
Published: 2010
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46. NO2 column amounts from ground‐based Pandora and MFDOAS spectrometers using the direct‐sun DOAS technique: Intercomparisons and application to OMI validation

Author: Herman, Jay, primary, Cede, Alexander, additional, Spinei, Elena, additional, Mount, George, additional, Tzortziou, Maria, additional, and Abuhassan, Nader, additional
Published: 2009
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47. Direct Sun measurements of NO2 column abundances from Table Mountain, California: Intercomparison of low- and high-resolution spectrometers.

Author: Wang, Shuhui, Pongetti, Thomas J., Sander, Stanley P., Spinei, Elena, Mount, George H., Cede, Alexander, and Herman, Jay
Published: 2010
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48. Validation of ozone monitoring instrument SO2 measurements in the Okmok volcanic cloud over Pullman, WA, July 2008.

Author: Spinei, Elena, Carn, Simon A., Krotkov, Nickolay A., Mount, George H., Yang, Kai, and Krueger, Arlin
Published: 2010
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49. NO2 column amounts from ground-based Pandora and MFDOAS spectrometers using the direct-sun DOAS technique: Intercomparisons and application to OMI validation.

Author: Herman, Jay, Cede, Alexander, Spinei, Elena, Mount, George, Tzortziou, Maria, and Abuhassan, Nader
Published: 2009
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50. Comparison of algorithms for the retrieval of aerosol and trace gas vertical profiles using synthetic MAX-DOAS data.

Author: Frieß, Udo, Beirle, Steffen, Bonilla, Leonardo Alvarado, Bösch, Tim, Fayt, Caroline, Friedrich, Martina M., Hendrick, François, Piters, Ankie, Richter, Andreas, van Roozendael, Michel, Spinei, Elena, Tirpitz, Jan-Lukas, Vlemmix, Tim, Wagner, Thomas, and Yang Wang
Published: 2018

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