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Browsing by Author "Spinei, Elena"

Now showing 1 - 4 of 4
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    Can Column Formaldehyde Observations Inform Air Quality Monitoring Strategies for Ozone and Related Photochemical Oxidants?
    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 (American Geophysical Union, 2022-07-16)
    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.
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    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
    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 (2021-01-28)
    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.
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    A feasibility study to use machine learning as an inversion algorithm for aerosol profile and property retrieval from multi-axis differential absorption spectroscopy measurements
    Dong, Yun; Spinei, Elena; Karpatne, Anuj (2020-10-16)
    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.
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    Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV–visible spectrometers during CINDI-2
    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 (2020-05-06)
    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.