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  • 1
    Online Resource
    Online Resource
    The NASA Atmospheric Tomography (ATom) Mission: Imaging the Chemistry of the Global Atmosphere
    American Meteorological Society ; 2022
    In:  Bulletin of the American Meteorological Society Vol. 103, No. 3 ( 2022-03), p. E761-E790
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 103, No. 3 ( 2022-03), p. E761-E790
    Abstract: This article provides an overview of the NASA Atmospheric Tomography (ATom) mission and a summary of selected scientific findings to date. ATom was an airborne measurements and modeling campaign aimed at characterizing the composition and chemistry of the troposphere over the most remote regions of the Pacific, Southern, Atlantic, and Arctic Oceans, and examining the impact of anthropogenic and natural emissions on a global scale. These remote regions dominate global chemical reactivity and are exceptionally important for global air quality and climate. ATom data provide the in situ measurements needed to understand the range of chemical species and their reactions, and to test satellite remote sensing observations and global models over large regions of the remote atmosphere. Lack of data in these regions, particularly over the oceans, has limited our understanding of how atmospheric composition is changing in response to shifting anthropogenic emissions and physical climate change. ATom was designed as a global-scale tomographic sampling mission with extensive geographic and seasonal coverage, tropospheric vertical profiling, and detailed speciation of reactive compounds and pollution tracers. ATom flew the NASA DC-8 research aircraft over four seasons to collect a comprehensive suite of measurements of gases, aerosols, and radical species from the remote troposphere and lower stratosphere on four global circuits from 2016 to 2018. Flights maintained near-continuous vertical profiling of 0.15–13-km altitudes on long meridional transects of the Pacific and Atlantic Ocean basins. Analysis and modeling of ATom data have led to the significant early findings highlighted here.
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    URL: Article
    DOI: 10.1175/BAMS-D-20-0315.1
    DOI: 10.1175/BAMS-D-20-0315.2
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2022
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  • 2
    Online Resource
    Online Resource
    Ash Particles Detected in the Tropical Lower Stratosphere
    American Geophysical Union (AGU) ; 2018
    In:  Geophysical Research Letters Vol. 45, No. 20 ( 2018-10-28)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 45, No. 20 ( 2018-10-28)
    Abstract: Large (5 microns) ash particles detected in the tropical lowermost stratosphere Ash particles were from the Mount Kelud eruption and persisted in the stratosphere for 4 weeks The low ash particle concentration indicates a limited impact on ice clouds or radiation
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2018GL079605
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2018
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Photochemical evolution of the 2013 California Rim Fire: synergistic impacts of reactive hydrocarbons and enhanced oxidants
    Copernicus GmbH ; 2022
    In:  Atmospheric Chemistry and Physics Vol. 22, No. 6 ( 2022-04-01), p. 4253-4275
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 22, No. 6 ( 2022-04-01), p. 4253-4275
    Abstract: Abstract. Large wildfires influence regional atmospheric composition, but chemical complexity challenges model predictions of downwind impacts. Here, we elucidate key connections within gas-phase photochemistry and assess novel chemical processes via a case study of the 2013 California Rim Fire plume. Airborne in situ observations, acquired during the NASA Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) mission, illustrate the evolution of volatile organic compounds (VOCs), oxidants, and reactive nitrogen over 12 h of atmospheric aging. Measurements show rapid formation of ozone and peroxyacyl nitrates (PNs), sustained peroxide production, and prolonged enhancements in oxygenated VOCs and nitrogen oxides (NOx). Observations and Lagrangian trajectories constrain a 0-D puff model that approximates plume photochemical history and provides a framework for evaluating process interactions. Simulations examine the effects of (1) previously unmeasured reactive VOCs identified in recent laboratory studies and (2) emissions and secondary production of nitrous acid (HONO). Inclusion of estimated unmeasured VOCs leads to a 250 % increase in OH reactivity and a 70 % increase in radical production via oxygenated VOC photolysis. HONO amplifies radical cycling and serves as a downwind NOx source, although impacts depend on how HONO is introduced. The addition of initial HONO (representing primary emissions) or particulate nitrate photolysis amplifies ozone production, while heterogeneous conversion of NO2 suppresses ozone formation. Analysis of radical initiation rates suggests that oxygenated VOC photolysis is a major radical source, exceeding HONO photolysis when averaged over the first 2 h of aging. Ozone production chemistry transitions from VOC sensitive to NOx sensitive within the first hour of plume aging, with both peroxide and organic nitrate formation contributing significantly to radical termination. To simulate smoke plume chemistry accurately, models should simultaneously account for the full reactive VOC pool and all relevant oxidant sources.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    URL: Article
    DOI: 10.5194/acp-22-4253-2022
    DOI: 10.5194/acp-22-4253-2022-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
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  • 4
    Online Resource
    Online Resource
    Ice nucleation and dehydration in the Tropical Tropopause Layer
    Proceedings of the National Academy of Sciences ; 2013
    In:  Proceedings of the National Academy of Sciences Vol. 110, No. 6 ( 2013-02-05), p. 2041-2046
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 110, No. 6 ( 2013-02-05), p. 2041-2046
    Abstract: Optically thin cirrus near the tropical tropopause regulate the humidity of air entering the stratosphere, which in turn has a strong influence on the Earth’s radiation budget and climate. Recent high-altitude, unmanned aircraft measurements provide evidence for two distinct classes of cirrus formed in the tropical tropopause region: ( i ) vertically extensive cirrus with low ice number concentrations, low extinctions, and large supersaturations (up to ∼70%) with respect to ice; and ( ii ) vertically thin cirrus layers with much higher ice concentrations that effectively deplete the vapor in excess of saturation. The persistent supersaturation in the former class of cirrus is consistent with the long time-scales (several hours or longer) for quenching of vapor in excess of saturation given the low ice concentrations and cold tropical tropopause temperatures. The low-concentration clouds are likely formed on a background population of insoluble particles with concentrations less than 100 L −1 (often less than 20 L −1 ), whereas the high ice concentration layers (with concentrations up to 10,000 L −1 ) can only be produced by homogeneous freezing of an abundant population of aqueous aerosols. These measurements, along with past high-altitude aircraft measurements, indicate that the low-concentration cirrus occur frequently in the tropical tropopause region, whereas the high-concentration cirrus occur infrequently. The predominance of the low-concentration clouds means cirrus near the tropical tropopause may typically allow entry of air into the stratosphere with as much as ∼1.7 times the ice saturation mixing ratio.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1217104110
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2013
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    SSG: 11
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Ubiquitous influence of waves on tropical high cirrus clouds
    American Geophysical Union (AGU) ; 2016
    In:  Geophysical Research Letters Vol. 43, No. 11 ( 2016-06-16), p. 5895-5901
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 43, No. 11 ( 2016-06-16), p. 5895-5901
    Abstract: Extensive airborne measurements reveal widespread influence of waves on tropical high cirrus clouds Cirrus clouds preferentially occur at cold anomalies with ongoing cooling Vertical scales of waves affect vertical scales of cirrus layers
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Issue
    URL: Article
    DOI: 10.1002/grl.v43.11
    DOI: 10.1002/2016GL069293
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2016
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 6
    Online Resource
    Online Resource
    Mixing events revealed by anomalous tracer relationships in the Arctic vortex during winter 1999/2000
    American Geophysical Union (AGU) ; 2002
    In:  Journal of Geophysical Research: Atmospheres Vol. 107, No. D24 ( 2002-12-27)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 107, No. D24 ( 2002-12-27)
    Abstract: During the 1999/2000 Arctic winter SAGE III–Ozone Loss and Validation Experiment (SOLVE) campaign, high‐resolution, in situ tracer data measured aboard the NASA ER‐2 high‐altitude aircraft revealed anomalous mixing events within the polar vortex. From January to March 2000 in the 350–500 K potential temperature range, we found mixing events during 15% of the flight time on average with significant maxima at potential temperatures of 450, 410, and 380 K. The events were spread throughout the vortex but showed a distinct minimum at 73° N and a peak at 85°N equivalent latitude. About 60% of the observed mixing events were less than 13 km wide. Based on a case study of tracer‐tracer relationships, an objective simple method is introduced to detect such events using the linear nitrous oxide (N 2 O):potential temperature relationship observed deep in the vortex. Rigorous analysis and supporting evidence from total water data corroborated the validity of the method. These results suggest mixing across the polar vortex edge occurred preferentially in layers at select altitudes in the Arctic winter 1999/2000.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2002JD002380
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2002
    detail.hit.zdb_id: 2033040-6
    detail.hit.zdb_id: 3094104-0
    detail.hit.zdb_id: 2130824-X
    detail.hit.zdb_id: 2016813-5
    detail.hit.zdb_id: 2016810-X
    detail.hit.zdb_id: 2403298-0
    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 161666-3
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 3094181-7
    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Missing OH reactivity in the global marine boundary layer
    Copernicus GmbH ; 2020
    In:  Atmospheric Chemistry and Physics Vol. 20, No. 6 ( 2020-04-02), p. 4013-4029
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 20, No. 6 ( 2020-04-02), p. 4013-4029
    Abstract: Abstract. The hydroxyl radical (OH) reacts with thousands of chemical species in the atmosphere, initiating their removal and the chemical reaction sequences that produce ozone, secondary aerosols, and gas-phase acids. OH reactivity, which is the inverse of OH lifetime, influences the OH abundance and the ability of OH to cleanse the atmosphere. The NASA Atmospheric Tomography (ATom) campaign used instruments on the NASA DC-8 aircraft to measure OH reactivity and more than 100 trace chemical species. ATom presented a unique opportunity to test the completeness of the OH reactivity calculated from the chemical species measurements by comparing it to the measured OH reactivity over two oceans across four seasons. Although the calculated OH reactivity was below the limit of detection for the ATom instrument used to measure OH reactivity throughout much of the free troposphere, the instrument was able to measure the OH reactivity in and just above the marine boundary layer. The mean measured value of OH reactivity in the marine boundary layer across all latitudes and all ATom deployments was 1.9 s−1, which is 0.5 s−1 larger than the mean calculated OH reactivity. The missing OH reactivity, the difference between the measured and calculated OH reactivity, varied between 0 and 3.5 s−1, with the highest values over the Northern Hemisphere Pacific Ocean. Correlations of missing OH reactivity with formaldehyde, dimethyl sulfide, butanal, and sea surface temperature suggest the presence of unmeasured or unknown volatile organic compounds or oxygenated volatile organic compounds associated with ocean emissions.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-20-4013-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2092549-9
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  • 8
    Online Resource
    Online Resource
    Terrain Trapped Airflows and Precipitation Variability during an Atmospheric River Event
    American Meteorological Society ; 2020
    In:  Journal of Hydrometeorology Vol. 21, No. 2 ( 2020-02), p. 355-375
    Details
    In: Journal of Hydrometeorology, American Meteorological Society, Vol. 21, No. 2 ( 2020-02), p. 355-375
    Abstract: We examine thermodynamic and kinematic structures of terrain trapped airflows (TTAs) during an atmospheric river (AR) event impacting Northern California 10–11 March 2016 using Alpha Jet Atmospheric eXperiment (AJAX) aircraft data, in situ observations, and Weather and Research Forecasting (WRF) Model simulations. TTAs are identified by locally intensified low-level winds flowing parallel to the coastal ranges and having maxima over the near-coastal waters. Multiple mechanisms can produce TTAs, including terrain blocking and gap flows. The changes in winds can significantly alter the distribution, timing, and intensity of precipitation. We show here how different mechanisms producing TTAs evolve during this event and influence local precipitation variations. Three different periods are identified from the time-varying wind fields. During period 1 (P1), a TTA develops during synoptic-scale onshore flow that backs to southerly flow near the coast. This TTA occurs when the Froude number (Fr) is less than 1, suggesting low-level terrain blocking is the primary mechanism. During period 2 (P2), a Petaluma offshore gap flow develops, with flows turning parallel to the coast offshore and with Fr 〉 1. Periods P1 and P2 are associated with slightly more coastal than mountain precipitation. In period 3 (P3), the gap flow initiated during P2 merges with a pre-cold-frontal low-level jet (LLJ) and enhanced precipitation shifts to higher mountain regions. Dynamical mixing also becomes more important as the TTA becomes confluent with the approaching LLJ. The different mechanisms producing TTAs and their effects on precipitation pose challenges to observational and modeling systems needed to improve forecasts and early warnings of AR events.
    Type of Medium: Online Resource
    ISSN: 1525-755X , 1525-7541
    URL: Article
    URL: Article
    DOI: 10.1175/JHM-D-19-0040.1
    DOI: 10.1175/jhm-d-19-0040.s1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 2042176-X
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  • 9
    Online Resource
    Online Resource
    A New Instrumented Airborne Platform for Atmospheric Research
    American Meteorological Society ; 2016
    In:  Bulletin of the American Meteorological Society Vol. 97, No. 3 ( 2016-03-01), p. 397-404
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 97, No. 3 ( 2016-03-01), p. 397-404
    Abstract: The NASA Ames Research Center operates a new research platform for atmospheric studies: an instrumented Alpha Jet. The present complement of instruments allows for the determination of carbon dioxide, ozone, water vapor, and methane concentrations as well as measurements of three-dimensional wind speeds, temperature, and pressure. Planned future instrumentation includes an Air-Core sampler and an instrument to measure formaldehyde. We give examples of measurements that have been made, including measurements carried out during a downward spiral over an expected methane source. An attractive property of this airborne system is its ability to respond rapidly to unexpected atmospheric events such as large forest fires or severe air quality events.
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    DOI: 10.1175/BAMS-D-14-00241.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2016
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
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  • 10
    Online Resource
    Online Resource
    Quantification of CO〈sub〉2〈/sub〉 and CH〈sub〉4〈/sub〉 emissions over Sacramento, California, based on divergence theorem using aircraft measurements
    Copernicus GmbH ; 2019
    In:  Atmospheric Measurement Techniques Vol. 12, No. 5 ( 2019-05-29), p. 2949-2966
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 12, No. 5 ( 2019-05-29), p. 2949-2966
    Abstract: Abstract. Emission estimates of carbon dioxide (CO2) and methane (CH4) and the meteorological factors affecting them are investigated over Sacramento, California, using an aircraft equipped with a cavity ring-down greenhouse gas sensor as part of the Alpha Jet Atmospheric eXperiment (AJAX) project. To better constrain the emission fluxes, we designed flights in a cylindrical pattern and computed the emission fluxes from two flights using a kriging method and Gauss's divergence theorem. Differences in wind treatment and assumptions about background concentrations affect the emission estimates by a factor of 1.5 to 7. The uncertainty is also impacted by meteorological conditions and distance from the emission sources. The vertical layer averaging affects the flux estimate, but the choice of raw wind or mass-balanced wind is more important than the thickness of the vertical averaging for mass-balanced wind for both urban and local scales. The importance of vertical mass transfer for flux estimates is examined, and the difference in the total emission estimate with and without vertical mass transfer is found to be small, especially at the local scale. The total flux estimates accounting for the entire circumference are larger than those based solely on measurements made in the downwind region. This indicates that a closed-shape flight profile can better contain total emissions relative to a one-sided curtain flight because most cities have more than one point source and wind direction can change with time and altitude. To reduce the uncertainty of the emission estimate, it is important that the sampling strategy account not only for known source locations but also possible unidentified sources around the city. Our results highlight that aircraft-based measurements using a closed-shape flight pattern are an efficient and useful strategy for identifying emission sources and estimating local- and city-scale greenhouse gas emission fluxes.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    URL: Article
    DOI: 10.5194/amt-12-2949-2019
    DOI: 10.5194/amt-12-2949-2019-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2505596-3
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