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  • 1
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    Online Resource
    In situ and space‐based observations of the Kelud volcanic plume: The persistence of ash in the lower stratosphere
    American Geophysical Union (AGU) ; 2016
    In:  Journal of Geophysical Research: Atmospheres Vol. 121, No. 18 ( 2016-09-27)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 121, No. 18 ( 2016-09-27)
    Abstract: In situ and spaceborne observations of the Kelud plume Persistence of ash in the lower stratosphere Ash can impact climate on longer time scale than previously thought
    Type of Medium: Online Resource
    ISSN: 2169-897X , 2169-8996
    URL: Issue
    URL: Article
    DOI: 10.1002/jgrd.v121.18
    DOI: 10.1002/2016JD025344
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2016
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    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 2969341-X
    SSG: 16,13
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  • 2
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    An Automated Common Algorithm for Planetary Boundary Layer Retrievals Using Aerosol Lidars in Support of the U.S. EPA Photochemical Assessment Monitoring Stations Program
    American Meteorological Society ; 2020
    In:  Journal of Atmospheric and Oceanic Technology Vol. 37, No. 10 ( 2020-10-01), p. 1847-1864
    Details
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 37, No. 10 ( 2020-10-01), p. 1847-1864
    Abstract: A unique automated planetary boundary layer (PBL) retrieval algorithm is proposed as a common cross-platform method for use with commercially available ceilometers for implementation under the redesigned U.S. Environmental Protection Agency Photochemical Assessment Monitoring Stations program. This algorithm addresses instrument signal quality and screens for precipitation and cloud layers before the implementation of the retrieval method using the Haar wavelet covariance transform. Layer attribution for the PBL height is supported with the use of continuation and time-tracking parameters, and uncertainties are calculated for individual PBL height retrievals. Commercial ceilometer retrievals are tested against radiosonde PBL height and cloud-base height during morning and late-afternoon transition times, critical to air quality model prediction and when retrieval algorithms struggle to identify PBL heights. A total of 58 radiosonde profiles were used, and retrievals for nocturnal stable layers, residual layers, and mixing layers were assessed. Overall good agreement was found for all comparisons, with one system showing limitations for the cases of nighttime surface stable layers and daytime mixing layer. It is recommended that nighttime shallow stable-layer retrievals be performed with a recommended minimum height or with additional verification. Retrievals of residual-layer heights and mixing-layer comparisons revealed overall good correlations with radiosonde heights (square of correlation coefficients r 2 ranging from 0.89 to 0.96, and bias ranging from approximately −131 to +63 m for the residual layer and r 2 from 0.88 to 0.97 and bias from −119 to +101 m for the mixing layer).
    Type of Medium: Online Resource
    ISSN: 0739-0572 , 1520-0426
    URL: Article
    DOI: 10.1175/JTECH-D-20-0050.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 2021720-1
    detail.hit.zdb_id: 48441-6
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  • 3
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    1-Alkyl-3-methylimidazolium Bis(perfluoroalkylsulfonyl)imide Water-Immiscible Ionic Liquids
    The Electrochemical Society ; 2004
    In:  Journal of The Electrochemical Society Vol. 151, No. 7 ( 2004), p. E219-
    Details
    In: Journal of The Electrochemical Society, The Electrochemical Society, Vol. 151, No. 7 ( 2004), p. E219-
    Type of Medium: Online Resource
    ISSN: 0013-4651
    URL: Article
    DOI: 10.1149/1.1751197
    RVK:
    VA 4000
    Language: English
    Publisher: The Electrochemical Society
    Publication Date: 2004
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  • 4
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    The first evaluation of formaldehyde column observations by improved Pandora spectrometers during the KORUS-AQ field study
    Copernicus GmbH ; 2018
    In:  Atmospheric Measurement Techniques Vol. 11, No. 9 ( 2018-08-31), p. 4943-4961
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 11, No. 9 ( 2018-08-31), p. 4943-4961
    Abstract: Abstract. The Korea–United States Air Quality Study (KORUS-AQ) 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 (37.5232∘ N, 27.1260∘ E; 26 m a.s.l.) and at a nearby rural site downwind of the city at the Mount Taehwa research forest site (37.3123∘ N, 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 and 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 vs. aircraft-integrated in situ data showed that Pandora values were larger by 16 % with a constant offset of 0.22 DU (Dobson units; 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=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.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-11-4943-2018
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2505596-3
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  • 5
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    Online Resource
    Evaluation of a method for converting Stratospheric Aerosol and Gas Experiment (SAGE) extinction coefficients to backscatter coefficients for intercomparison with lidar observations
    Copernicus GmbH ; 2020
    In:  Atmospheric Measurement Techniques Vol. 13, No. 8 ( 2020-08-13), p. 4261-4276
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 13, No. 8 ( 2020-08-13), p. 4261-4276
    Abstract: Abstract. Aerosol backscatter coefficients were calculated using multiwavelength aerosol extinction products from the SAGE II and III/ISS instruments (SAGE: Stratospheric Aerosol and Gas Experiment). The conversion methodology is presented, followed by an evaluation of the conversion algorithm's robustness. The SAGE-based backscatter products were compared to backscatter coefficients derived from ground-based lidar at three sites (Table Mountain Facility, Mauna Loa, and Observatoire de Haute-Provence). Further, the SAGE-derived lidar ratios were compared to values from previous balloon and theoretical studies. This evaluation includes the major eruption of Mt. Pinatubo in 1991, followed by the atmospherically quiescent period beginning in the late 1990s. Recommendations are made regarding the use of this method for evaluation of aerosol extinction profiles collected using the occultation method.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-13-4261-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2505596-3
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  • 6
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    Intercomparison of Pandora stratospheric NO〈sub〉2〈/sub〉 slant column product with the NDACC-certified M07 spectrometer in Lauder, New Zealand
    Copernicus GmbH ; 2017
    In:  Atmospheric Measurement Techniques Vol. 10, No. 11 ( 2017-11-15), p. 4363-4372
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 10, No. 11 ( 2017-11-15), p. 4363-4372
    Abstract: Abstract. In September 2014, a Pandora multi-spectral photometer operated by the SAGE-III project was sent to Lauder, New Zealand, to operate side-by-side with the National Institute of Water and Atmospheric Research's (NIWA) Network for Detection of Atmospheric Composition Change (NDACC) certified zenith slant column NO2 instrument to allow intercomparison between the two instruments and for evaluation of the Pandora unit as a potential SAGE-III validation tool for stratospheric NO2. This intercomparison spanned a full year, from September 2014 to September 2015. Both datasets were produced using their respective native algorithms using a common reference spectrum (i.e., 12:00 NZDT (UTC + 13) on 26 February 2015). Throughout the entire deployment period both instruments operated in a zenith-only observation configuration. Though conversion from slant column density (SCD) to vertical-column density is routine (by application of an air mass factor), we limit the current analysis to SCD only. This omission is beneficial in that it provides an intercomparison based on similar modes of operation for the two instruments and the retrieval algorithms as opposed to introducing an air mass factor dependence in the intercomparison as well. It was observed that the current hardware configurations and retrieval algorithms are in good agreement (R 〉 0.95). The detailed results of this investigation are presented herein.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-10-4363-2017
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
    detail.hit.zdb_id: 2505596-3
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  • 7
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    Online Resource
    Demonstration of an off-axis parabolic receiver for near-range retrieval of lidar ozone profiles
    Copernicus GmbH ; 2019
    In:  Atmospheric Measurement Techniques Vol. 12, No. 1 ( 2019-01-18), p. 363-370
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 12, No. 1 ( 2019-01-18), p. 363-370
    Abstract: Abstract. During the 2017 Ozone Water Land Environmental Transition Study (OWLETS), the Langley mobile ozone lidar system utilized a new small diameter receiver to improve the retrieval of near-surface signals from 0.1 to 1 km in altitude. This new receiver utilizes a single 90 ∘ fiber-coupled, off-axis parabolic mirror resulting in a compact form that is easy to align. The single reflective surface offers the opportunity to easily expand its use to multiple wavelengths for additional measurement channels such as visible wavelength aerosol measurements. Detailed results compare the performance of the receiver to both ozonesonde and in situ measurements from a UAV platform, validating the performance of the near-surface ozone retrievals. Absolute O3 differences averaged 7 % between lidar and ozonesonde data from 0.1 to 1.0 km and yielded a 2.3 % high bias in the lidar data, well within the uncertainty of the sonde measurements. Conversely, lidar O3 measurements from 0.1 to 0.2 km averaged 10.5 % lower than coincident UAV O3. A more detailed study under more stable atmospheric conditions would be necessary to resolve the residual instrument differences reported in this work. Nevertheless, this unique added capability is a significant improvement allowing for near-surface observation of ozone.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-12-363-2019
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2505596-3
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  • 8
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    Online Resource
    SAGE III/ISS aerosol/cloud categorization and its impact on GloSSAC
    Copernicus GmbH ; 2023
    In:  Atmospheric Measurement Techniques Vol. 16, No. 10 ( 2023-06-01), p. 2709-2731
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 16, No. 10 ( 2023-06-01), p. 2709-2731
    Abstract: Abstract. The Stratospheric Aerosol and Gas Experiment on the International Space Station (SAGE III/ISS) began its mission in June 2017. SAGE III/ISS is an updated version of the SAGE III on Meteor (SAGE III/M3M) instrument and makes observations of the stratospheric aerosol extinction coefficient at wavelengths that range from 385 to 1550 nm with a near-global coverage between 60∘ S and 60∘ N. While SAGE III/ISS makes reliable and robust solar occultation measurements in the stratosphere, similar to its predecessors, interpreting aerosol extinction measurements in the vicinity of the tropopause and in the troposphere has been a challenge for all SAGE instruments because of the potential for cloud interference. Herein, we discuss some of the challenges associated with discriminating between aerosols and clouds within the extinction measurements and describe the methods implemented to categorize clouds and aerosols using available SAGE III/ISS aerosol measurements. This cloud/aerosol categorization method is based on the results of Thomason and Vernier (2013), with some modifications that now incorporate the influence of recent volcanic/pyrocumulonimbus (PyroCb) events. Herein we describe this new cloud/aerosol categorization algorithm, demonstrate how it identifies enhanced aerosols and aerosol–cloud mixture in the lower stratospheric region, and discuss the impact of this cloud-filtering algorithm on the latest release of the Global Space-based Stratospheric Aerosol Climatology (GloSSAC) data set.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    URL: Article
    DOI: 10.5194/amt-16-2709-2023
    DOI: 10.5194/amt-16-2709-2023-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2023
    detail.hit.zdb_id: 2505596-3
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  • 9
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    Taehwa Research Forest: a receptor site for severe domestic pollution events in Korea during 2016
    Copernicus GmbH ; 2019
    In:  Atmospheric Chemistry and Physics Vol. 19, No. 7 ( 2019-04-12), p. 5051-5067
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 19, No. 7 ( 2019-04-12), p. 5051-5067
    Abstract: Abstract. During the May–June 2016 International Cooperative Air Quality Field Study in Korea (KORUS-AQ), light synoptic meteorological forcing facilitated Seoul metropolitan pollution outflow to reach the remote Taehwa Research Forest (TRF) site and cause regulatory exceedances of ozone on 24 days. Two of these severe pollution events are thoroughly examined. The first, occurring on 17 May 2016, tracks transboundary pollution transport exiting eastern China and the Yellow Sea, traversing the Seoul Metropolitan Area (SMA), and then reaching TRF in the afternoon hours with severely polluted conditions. This case study indicates that although outflow from China and the Yellow Sea were elevated with respect to chemically unperturbed conditions, the regulatory exceedance at TRF was directly linked in time, space, and altitude to urban Seoul emissions. The second case studied, which occurred on 9 June 2016, reveals that increased levels of biogenic emissions, in combination with amplified urban emissions, were associated with severe levels of pollution and a regulatory exceedance at TRF. In summary, domestic emissions may be causing more pollution than by transboundary pathways, which have been historically believed to be the major source of air pollution in South Korea. The case studies are assessed with multiple aircraft, model (photochemical and meteorological) simulations, in situ chemical sampling, and extensive ground-based profiling at TRF. These observations clearly identify TRF and the surrounding rural communities as receptor sites for severe pollution events associated with Seoul outflow, which will result in long-term negative effects to both human health and agriculture in the affected areas.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-19-5051-2019
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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  • 10
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    Comprehensive evaluations of diurnal NO〈sub〉2〈/sub〉 measurements during DISCOVER-AQ 2011: effects of resolution-dependent representation of NO〈sub〉〈i〉x〈/i〉〈/sub〉 emissions
    Copernicus GmbH ; 2021
    In:  Atmospheric Chemistry and Physics Vol. 21, No. 14 ( 2021-07-23), p. 11133-11160
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 21, No. 14 ( 2021-07-23), p. 11133-11160
    Abstract: Abstract. Nitrogen oxides (NOx = NO + NO2) play a crucial role in the formation of ozone and secondary inorganic and organic aerosols, thus affecting human health, global radiation budget, and climate. The diurnal and spatial variations in NO2 are functions of emissions, advection, deposition, vertical mixing, and chemistry. Their observations, therefore, provide useful constraints in our understanding of these factors. We employ a Regional chEmical and trAnsport model (REAM) to analyze the observed temporal (diurnal cycles) and spatial distributions of NO2 concentrations and tropospheric vertical column densities (TVCDs) using aircraft in situ measurements and surface EPA Air Quality System (AQS) observations as well as the measurements of TVCDs by satellite instruments (OMI: the Ozone Monitoring Instrument; GOME-2A: Global Ozone Monitoring Experiment – 2A), ground-based Pandora, and the Airborne Compact Atmospheric Mapper (ACAM) instrument in July 2011 during the DISCOVER-AQ campaign over the Baltimore–Washington region. The model simulations at 36 and 4 km resolutions are in reasonably good agreement with the regional mean temporospatial NO2 observations in the daytime. However, we find significant overestimations (underestimations) of model-simulated NO2 (O3) surface concentrations during nighttime, which can be mitigated by enhancing nocturnal vertical mixing in the model. Another discrepancy is that Pandora-measured NO2 TVCDs show much less variation in the late afternoon than simulated in the model. The higher-resolution 4 km simulations tend to show larger biases compared to the observations due largely to the larger spatial variations in NOx emissions in the model when the model spatial resolution is increased from 36 to 4 km. OMI, GOME-2A, and the high-resolution aircraft ACAM observations show a more dispersed distribution of NO2 vertical column densities (VCDs) and lower VCDs in urban regions than corresponding 36 and 4 km model simulations, likely reflecting the spatial distribution bias of NOx emissions in the National Emissions Inventory (NEI) 2011.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    URL: Article
    DOI: 10.5194/acp-21-11133-2021
    DOI: 10.5194/acp-21-11133-2021-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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