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  • 1
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    Online Resource
    Multi-decadal surface ozone trends at globally distributed remote locations
    University of California Press ; 2020
    In:  Elem Sci Anth Vol. 8 ( 2020-01-01)
    Details
    In: Elem Sci Anth, University of California Press, Vol. 8 ( 2020-01-01)
    Abstract: Extracting globally representative trend information from lower tropospheric ozone observations is extremely difficult due to the highly variable distribution and interannual variability of ozone, and the ongoing shift of ozone precursor emissions from high latitudes to low latitudes. Here we report surface ozone trends at 27 globally distributed remote locations (20 in the Northern Hemisphere, 7 in the Southern Hemisphere), focusing on continuous time series that extend from the present back to at least 1995. While these sites are only representative of less than 25% of the global surface area, this analysis provides a range of regional long-term ozone trends for the evaluation of global chemistry-climate models. Trends are based on monthly mean ozone anomalies, and all sites have at least 20 years of data, which improves the likelihood that a robust trend value is due to changes in ozone precursor emissions and/or forced climate change rather than naturally occurring climate variability. Since 1995, the Northern Hemisphere sites are nearly evenly split between positive and negative ozone trends, while 5 of 7 Southern Hemisphere sites have positive trends. Positive trends are in the range of 0.5–2 ppbv decade–1, with ozone increasing at Mauna Loa by roughly 50% since the late 1950s. Two high elevation Alpine sites, discussed by previous assessments, exhibit decreasing ozone trends in contrast to the positive trend observed by IAGOS commercial aircraft in the European lower free-troposphere. The Alpine sites frequently sample polluted European boundary layer air, especially in summer, and can only be representative of lower free tropospheric ozone if the data are carefully filtered to avoid boundary layer air. The highly variable ozone trends at these 27 surface sites are not necessarily indicative of free tropospheric trends, which have been overwhelmingly positive since the mid-1990s, as shown by recent studies of ozonesonde and aircraft observations.
    Type of Medium: Online Resource
    ISSN: 2325-1026
    URL: Article
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    DOI: 10.1525/elementa.420
    DOI: 10.1525/elementa.420.s1
    DOI: 10.1525/elementa.420.t1
    DOI: 10.1525/elementa.420.t2
    DOI: 10.1525/elementa.420.t3
    DOI: 10.1525/elementa.420.f1
    DOI: 10.1525/elementa.420.f2
    DOI: 10.1525/elementa.420.f3
    DOI: 10.1525/elementa.420.f4
    DOI: 10.1525/elementa.420.f5
    DOI: 10.1525/elementa.420.f6
    DOI: 10.1525/elementa.420.f7
    DOI: 10.1525/elementa.420.f8
    DOI: 10.1525/elementa.420.f9
    DOI: 10.1525/elementa.420.f10
    Language: English
    Publisher: University of California Press
    Publication Date: 2020
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  • 2
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    Observations of Entrainment in Eastern Pacific Marine Stratocumulus Using Three Conserved Scalars
    American Meteorological Society ; 2005
    In:  Journal of the Atmospheric Sciences Vol. 62, No. 9 ( 2005-09-01), p. 3268-3285
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 62, No. 9 ( 2005-09-01), p. 3268-3285
    Abstract: Fast measurements of three scalars, ozone, dimethyl sulfide (DMS), and total water, are used to investigate the entrainment process in the stratocumulus-topped boundary layer (STBL) observed over the eastern subtropical Pacific during the second Dynamics and Chemistry of Marine Stratocumulus Experiment (DYCOMS-II). Direct measurement of the flux profiles by eddy covariance is used to estimate the entrainment velocity, the average rate at which the boundary layer grows diabatically via incorporation of overlying free tropospheric air. The entrainment velocities observed over the course of the mission, which took place during July 2001, ranged from 0.12 to 0.72 cm s−1, and appear to outpace the estimated large-scale subsidence as the boundary layer advects over warmer sea surface temperatures. Observed entrainment velocities display only a weak correlation with the buoyancy Richardson number defined at the inversion, which suggests that processes other than inversion strength, such as wind shear, might play a larger role in driving entrainment in the STBL than previously recognized. This study is the first to use DMS as an entrainment tracer because the high-rate mass spectrometric technique has only recently been developed. The biogenic sulfur compound shows great promise for such investigations in marine environments because the free tropospheric concentrations are virtually nonexistent, and it therefore serves as an unambiguous marker of boundary layer air. As such, individual mixing events can be analyzed to determine the mixing fraction of boundary layer and free tropospheric air, and in several such cases buoyancy reversal was observed despite the absence of large-scale dissipation of the cloud field as postulated by cloud-top entrainment instability. Moreover, the redundancy attained in using three separate scalars allows for an investigation of the average height scales above the inversion from where air is blended into the STBL, and this tends to be less than 80 m above the mean inversion height, implying that the entrainment process occurs on very small scales.
    Type of Medium: Online Resource
    ISSN: 1520-0469 , 0022-4928
    URL: Article
    DOI: 10.1175/JAS3541.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2005
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  • 3
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    Ozone Transport to the San Joaquin Valley: Baseline Observations from CABOTS
    American Meteorological Society ; 2020
    In:  Bulletin of the American Meteorological Society Vol. 101, No. 5 ( 2020-05), p. 385-388
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 101, No. 5 ( 2020-05), p. 385-388
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    DOI: 10.1175/BAMS-D-18-0302.A
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
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  • 4
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    Deep convection as a source of new particles in the midlatitude upper troposphere
    American Geophysical Union (AGU) ; 2002
    In:  Journal of Geophysical Research: Atmospheres Vol. 107, No. D21 ( 2002-11-16)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 107, No. D21 ( 2002-11-16)
    Abstract: A case study of new particle formation in the region downwind of a mesoscale convective system stretching across much of the central United States is presented. Airborne measurements were made of condensation nuclei (CN), cloud particle surface area, water vapor, and other gases. CN concentrations were greatly enhanced above and downwind of the cirrus anvil, with maximum concentrations of 45,000 per standard cm 3 . Volatility and electron microscope measurements indicated that most of the particles were likely to be small sulfate particles. The enhancement extended over at least a 600‐km region. Multivariate statistical analysis revealed that high CN concentrations were associated with surface tracers, as well as convective elements. Convection apparently brings gas‐phase particle precursors from the surface to the storm outflow region, where particle nucleation is favored by the extremely low temperatures. Simple calculations showed that deep convective systems may contribute to a substantial portion of the background aerosol in the upper troposphere at midlatitudes.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2001JD000323
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2002
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    SSG: 16,13
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  • 5
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    Airborne Quantification of Methane Emissions over the Four Corners Region
    American Chemical Society (ACS) ; 2017
    In:  Environmental Science & Technology Vol. 51, No. 10 ( 2017-05-16), p. 5832-5837
    Details
    In: Environmental Science & Technology, American Chemical Society (ACS), Vol. 51, No. 10 ( 2017-05-16), p. 5832-5837
    Type of Medium: Online Resource
    ISSN: 0013-936X , 1520-5851
    URL: Article
    URL: Article
    DOI: 10.1021/acs.est.6b06107
    DOI: 10.1021/acs.est.6b06107.s001
    RVK:
    AR 10100
    Language: English
    Publisher: American Chemical Society (ACS)
    Publication Date: 2017
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  • 6
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    Sulfur processing in the marine atmospheric boundary layer: A review and critical assessment of modeling uncertainties
    Elsevier BV ; 2009
    In:  Atmospheric Environment Vol. 43, No. 18 ( 2009-6), p. 2841-2854
    Details
    In: Atmospheric Environment, Elsevier BV, Vol. 43, No. 18 ( 2009-6), p. 2841-2854
    Type of Medium: Online Resource
    ISSN: 1352-2310
    URL: Article
    DOI: 10.1016/j.atmosenv.2009.02.043
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2009
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  • 7
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    Extrapolation of point measurements and fertilizer-only emission factors cannot capture statewide soil NO x emissions
    American Association for the Advancement of Science (AAAS) ; 2018
    In:  Science Advances Vol. 4, No. 9 ( 2018-09-07)
    Details
    In: Science Advances, American Association for the Advancement of Science (AAAS), Vol. 4, No. 9 ( 2018-09-07)
    Abstract: Maaz et al . argue that inconsistencies across scales of observation undermine our working hypothesis that soil NO x emissions have been substantially overlooked in California; however, the core issues they raise are already discussed in our manuscript. We agree that point measurements cannot be reliably used to estimate statewide soil NO x emissions—the principal motivation behind our new modeling/airplane approach. Maaz et al .’s presentation of fertilizer-based emission factors (a nonmechanistic scaling of point measures to regions based solely on estimated nitrogen fertilizer application rates) includes no data from California or other semiarid sites, and does not explicitly account for widely known controls of climate, soil, and moisture on soil NO x fluxes. In contrast, our model includes all of these factors. Finally, the fertilizer sales data that Maaz et al . highlight are known to suffer from serious errors and do not offer a logically more robust pathway for spatial analysis of NO x emissions from soil.
    Type of Medium: Online Resource
    ISSN: 2375-2548
    URL: Article
    DOI: 10.1126/sciadv.aau7373
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2018
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  • 8
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    Observational assessment of the role of nocturnal residual-layer chemistry in determining daytime surface particulate nitrate concentrations
    Copernicus GmbH ; 2017
    In:  Atmospheric Chemistry and Physics Vol. 17, No. 23 ( 2017-12-12), p. 14747-14770
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 17, No. 23 ( 2017-12-12), p. 14747-14770
    Abstract: Abstract. This study discusses an analysis of combined airborne and ground observations of particulate nitrate (NO3−(p)) concentrations made during the wintertime DISCOVER-AQ (Deriving Information on Surface Conditions from COlumn and VERtically resolved observations relevant to Air Quality) study at one of the most polluted cities in the United States – Fresno, CA – in the San Joaquin Valley (SJV) and focuses on developing an understanding of the various processes that impact surface nitrate concentrations during pollution events. The results provide an explicit case-study illustration of how nighttime chemistry can influence daytime surface-level NO3−(p) concentrations, complementing previous studies in the SJV. The observations exemplify the critical role that nocturnal chemical production of NO3−(p) aloft in the residual layer (RL) can play in determining daytime surface-level NO3−(p) concentrations. Further, they indicate that nocturnal production of NO3−(p) in the RL, along with daytime photochemical production, can contribute substantially to the buildup and sustaining of severe pollution episodes. The exceptionally shallow nocturnal boundary layer (NBL) heights characteristic of wintertime pollution events in the SJV intensify the importance of nocturnal production aloft in the residual layer to daytime surface concentrations. The observations also demonstrate that dynamics within the RL can influence the early-morning vertical distribution of NO3−(p), despite low wintertime wind speeds. This overnight reshaping of the vertical distribution above the city plays an important role in determining the net impact of nocturnal chemical production on local and regional surface-level NO3−(p) concentrations. Entrainment of clean free-tropospheric (FT) air into the boundary layer in the afternoon is identified as an important process that reduces surface-level NO3−(p) and limits buildup during pollution episodes. The influence of dry deposition of HNO3 gas to the surface on daytime particulate nitrate concentrations is important but limited by an excess of ammonia in the region, which leads to only a small fraction of nitrate existing in the gas phase even during the warmer daytime. However, in the late afternoon, when diminishing solar heating leads to a rapid fall in the mixed boundary layer height (BLH), the impact of surface deposition is temporarily enhanced and can lead to a substantial decline in surface-level particulate nitrate concentrations; this enhanced deposition is quickly arrested by a decrease in surface temperature, which drops the gas-phase fraction to near zero. The overall importance of enhanced late-afternoon gas-phase loss to the multiday buildup of pollution events is limited by the very shallow nocturnal boundary layer. The case study here demonstrates that mixing down of NO3−(p) from the RL can contribute a majority of the surface-level NO3−(p) in the morning (here,  ∼  80 %), and a strong influence can persist into the afternoon even when photochemical production is maximum. The particular day-to-day contribution of aloft nocturnal NO3−(p) production to surface concentrations will depend on prevailing chemical and meteorological conditions. Although specific to the SJV, the observations and conceptual framework further developed here provide general insights into the evolution of pollution episodes in wintertime environments.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    URL: Article
    DOI: 10.5194/acp-17-14747-2017
    DOI: 10.5194/acp-17-14747-2017-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
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  • 9
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    Intercomparison of lidar, aircraft, and surface ozone measurements in the San Joaquin Valley during the California Baseline Ozone Transport Study (CABOTS)
    Copernicus GmbH ; 2019
    In:  Atmospheric Measurement Techniques Vol. 12, No. 3 ( 2019-03-25), p. 1889-1904
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 12, No. 3 ( 2019-03-25), p. 1889-1904
    Abstract: Abstract. The California Baseline Ozone Transport Study (CABOTS) was conducted in the late spring and summer of 2016 to investigate the influence of long-range transport and stratospheric intrusions on surface ozone (O3) concentrations in California with emphasis on the San Joaquin Valley (SJV), one of two extreme ozone non-attainment areas in the US. One of the major objectives of CABOTS was to characterize the vertical distribution of O3 and aerosols above the SJV to aid in the identification of elevated transport layers and assess their surface impacts. To this end, the NOAA Earth System Research Laboratory (ESRL) deployed the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) mobile lidar to the Visalia Municipal Airport (36.315∘ N, 119.392∘ E) in the central SJV between 27 May and 7 August 2016. Here we compare the TOPAZ ozone retrievals with co-located in situ surface measurements and nearby regulatory monitors and also with airborne in situ measurements from the University of California at Davis–Scientific Aviation (SciAv) Mooney and NASA Alpha Jet Atmospheric eXperiment (AJAX) research aircraft. Our analysis shows that the lidar and aircraft measurements agree, on average to within 5 ppbv, the sum of their stated uncertainties of 3 and 2 ppbv, respectively.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-12-1889-2019
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
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  • 10
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    Measurements of isoprene nitrates above a forest canopy
    American Geophysical Union (AGU) ; 2001
    In:  Journal of Geophysical Research: Atmospheres Vol. 106, No. D20 ( 2001-10-27), p. 24429-24438
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 106, No. D20 ( 2001-10-27), p. 24429-24438
    Abstract: Measurements of atmospheric organic nitrates derived from isoprene, i.e., “isoprene nitrates”, were conducted from July 14 to August 19, 1998, as part of the 1998 summer intensive measurement campaign of the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport (PROPHET) at the University of Michigan Biological Station in Pellston, Michigan. The measurements were conducted using on‐line chromatography in conjunction with a nitrate‐selective detection scheme. Measured concentrations of isoprene nitrates ranged from 0.5 parts per trillion (ppt), the detection limit of the method employed, to 35 ppt. In this paper we discuss the contribution of the isoprene nitrates to NO y , which was typically 0.5–1.5% of total odd nitrogen, but up to ∼4% for well‐aged air. Concentrations of isoprene nitrates exhibited a strong diurnal variation consistent with their expected chemical and physical removal rates. In this work we also discuss the chemistry of the precursor peroxy radicals and the NO x dependence of isoprene nitrate formation.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2001JD900029
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2001
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