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  1. AU="Knowland, K E"
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  1. Article: Sub-City Scale Hourly Air Quality Forecasting by Combining Models, Satellite Observations, and Ground Measurements.

    Malings, C / Knowland, K E / Keller, C A / Cohn, S E

    Earth and space science (Hoboken, N.J.)

    2021  Volume 8, Issue 7, Page(s) e2021EA001743

    Abstract: While multiple information sources exist concerning surface-level air pollution, no individual source simultaneously provides large-scale spatial coverage, fine spatial and temporal resolution, and high accuracy. It is, therefore, necessary to integrate ... ...

    Abstract While multiple information sources exist concerning surface-level air pollution, no individual source simultaneously provides large-scale spatial coverage, fine spatial and temporal resolution, and high accuracy. It is, therefore, necessary to integrate multiple data sources, using the strengths of each source to compensate for the weaknesses of others. In this study, we propose a method incorporating outputs of NASA's GEOS Composition Forecasting model system with satellite information from the TROPOMI instrument and ground measurement data on surface concentrations. Although we use ground monitoring data from the Environmental Protection Agency network in the continental United States, the model and satellite data sources used have the potential to allow for global application. This method is demonstrated using surface measurements of nitrogen dioxide as a test case in regions surrounding five major US cities. The proposed method is assessed through cross-validation against withheld ground monitoring sites. In these assessments, the proposed method demonstrates major improvements over two baseline approaches which use ground-based measurements only. Results also indicate the potential for near-term updating of forecasts based on recent ground measurements.
    Language English
    Publishing date 2021-07-02
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2807271-6
    ISSN 2333-5084
    ISSN 2333-5084
    DOI 10.1029/2021EA001743
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Case study of stratospheric intrusion above Hampton, Virginia: Lidar-observation and modeling analysis

    Gronoff, G / Berkoff, T / Knowland, K.E / Lei, L / Shook, M / Fabbri, B / Carrion, W / Langford, A.O

    Elsevier Ltd Atmospheric environment. 2021 Aug. 15, v. 259

    2021  

    Abstract: On 2019-02-14, at 1:00 UTC, a large increase of ozone density at 8 km altitude was detected above Hampton, Virginia using the NASA Langley Mobile Ozone Lidar, LMOL. Ozone levels above 70 ppbv were observed down to an altitude of 4.5 km up to 5 h after ... ...

    Abstract On 2019-02-14, at 1:00 UTC, a large increase of ozone density at 8 km altitude was detected above Hampton, Virginia using the NASA Langley Mobile Ozone Lidar, LMOL. Ozone levels above 70 ppbv were observed down to an altitude of 4.5 km up to 5 h after the start of the event. The NASA GEOS Composition Forecast (GEOS-CF) model was used to investigate the hypothesis of a stratospheric intrusion (SI). The agreement between the model and the observations confirmed the stratospheric origin of the airmass and highlighted the capabilities of GEOS-CF to simulate intrusions. In parallel, MicroPulse Lidar (MPL) observations indicated that depolarizing particulates high in the troposphere showed downward motions linked to the intrusion. Since these particulates are linked to cirrus clouds, it is hypothesised that the SI led to an ice-virga effect. This might suggest that particulate observations can exhibit patterns of stratospheric intrusions and can be used, in certain cases, as a signature of the events. These particulates, likely ice crystals, have opposite distribution gradients compared to O₃ at their interface which could be explained by a non-mixing of stratospheric and tropospheric air-masses as well as destruction of O₃ by ice crystal-induced processes. Model-data comparison shows that if that latter effect exists, it has small consequences for the observed case. This work shows the capabilities of the LMOL system to detect SI and to validate the vertical and temporal modeling of SI by GEOS-CF, as well as showing that signatures of SI could be detected by MPL.
    Keywords altitude ; case studies ; ice ; lidar ; models ; ozone ; particulates ; stratosphere ; troposphere ; Virginia
    Language English
    Dates of publication 2021-0815
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 216368-8
    ISSN 0004-6981 ; 1352-2310
    ISSN 0004-6981 ; 1352-2310
    DOI 10.1016/j.atmosenv.2021.118498
    Database NAL-Catalogue (AGRICOLA)

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  3. Article: Stratospheric intrusion-influenced ozone air quality exceedances investigated in the NASA MERRA-2 Reanalysis.

    Knowland, K E / Ott, L E / Duncan, B N / Wargan, K

    Geophysical research letters

    2017  Volume 44, Issue 20, Page(s) 10691–10701

    Abstract: Stratospheric intrusions have been the interest of decades of research for their ability to bring stratospheric ozone ( ... ...

    Abstract Stratospheric intrusions have been the interest of decades of research for their ability to bring stratospheric ozone (O
    Language English
    Publishing date 2017-10-28
    Publishing country United States
    Document type Journal Article
    ZDB-ID 7403-2
    ISSN 0094-8276
    ISSN 0094-8276
    DOI 10.1002/2017gl074532
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Using networked Pandora observations to capture spatiotemporal changes in total column ozone associated with stratosphere-to-troposphere transport

    Robinson, J / Abuhassan, N / Cede, A / Connors, V / Knowland, K.E / Kotsakis, A / Labow, G / Santos, F / Swap, R / Tiefengraber, M / Tzortziou, M

    Elsevier B.V. Atmospheric research. 2020 July 01, v. 238

    2020  

    Abstract: Accurately capturing the evolution of episodic stratosphere-to-troposphere transport is critical due to the potential impacts on both climate and air quality. Until now, investigating associated spatiotemporal gradients in total column ozone (TCO) has ... ...

    Abstract Accurately capturing the evolution of episodic stratosphere-to-troposphere transport is critical due to the potential impacts on both climate and air quality. Until now, investigating associated spatiotemporal gradients in total column ozone (TCO) has primarily been the task of observations from polar-orbiting satellites as well as high-resolution models. We explore how a network of five ground-based Pandora spectrometer systems can be utilized in a similar fashion. The passage of a strong mid-latitude cyclone in March 2018 and its associated stratospheric intrusion is used as a case demonstrating the ability of networked Pandora observations to contextualize these regions of transport across space and time. Results show that the high temporal resolution of Pandora observations and the networked approach were able to resolve increases in TCO associated with stratosphere-to-troposphere transport and to capture the spatial context of the chosen episode. The use of networked Pandora observations shows promise for additional transport studies and for supporting future geostationary atmospheric composition satellite missions and modeling efforts.
    Keywords air quality ; climate ; latitude ; models ; ozone ; satellites ; space and time ; spectrometers ; stratosphere
    Language English
    Dates of publication 2020-0701
    Publishing place Elsevier B.V.
    Document type Article
    ISSN 0169-8095
    DOI 10.1016/j.atmosres.2020.104872
    Database NAL-Catalogue (AGRICOLA)

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  5. Article: NASA GEOS Composition Forecast Modeling System GEOS-CF v1.0: Stratospheric Composition.

    Knowland, K E / Keller, C A / Wales, P A / Wargan, K / Coy, L / Johnson, M S / Liu, J / Lucchesi, R A / Eastham, S D / Fleming, E / Liang, Q / Leblanc, T / Livesey, N J / Walker, K A / Ott, L E / Pawson, S

    Journal of advances in modeling earth systems

    2022  Volume 14, Issue 6, Page(s) e2021MS002852

    Abstract: The NASA Goddard Earth Observing System (GEOS) Composition Forecast (GEOS-CF) provides recent estimates and 5-day forecasts of atmospheric composition to the public in near-real time. To do this, the GEOS Earth system model is coupled with the GEOS-Chem ... ...

    Abstract The NASA Goddard Earth Observing System (GEOS) Composition Forecast (GEOS-CF) provides recent estimates and 5-day forecasts of atmospheric composition to the public in near-real time. To do this, the GEOS Earth system model is coupled with the GEOS-Chem tropospheric-stratospheric unified chemistry extension (UCX) to represent composition from the surface to the top of the GEOS atmosphere (0.01 hPa). The GEOS-CF system is described, including updates made to the GEOS-Chem UCX mechanism within GEOS-CF for improved representation of stratospheric chemistry. Comparisons are made against balloon, lidar, and satellite observations for stratospheric composition, including measurements of ozone (O
    Language English
    Publishing date 2022-06-07
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2462132-8
    ISSN 1942-2466
    ISSN 1942-2466
    DOI 10.1029/2021MS002852
    Database MEDical Literature Analysis and Retrieval System OnLINE

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