377 results on '"Ronald C. Cohen"'
Search Results
2. Direct Retrieval of NO2 Vertical Columns from UV-Vis (390-495 nm) Spectral Radiances Using a Neural Network
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Chi Li, Xiaoguang Xu, Xiong Liu, Jun Wang, Kang Sun, Jos van Geffen, Qindan Zhu, Jianzhong Ma, Junli Jin, Kai Qin, Qin He, Pinhua Xie, Bo Ren, and Ronald C. Cohen
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Environmental sciences ,GE1-350 ,Physical geography ,GB3-5030 - Abstract
Satellite retrievals of columnar nitrogen dioxide (NO2) are essential for the characterization of nitrogen oxides (NOx) processes and impacts. The requirements of modeled a priori profiles present an outstanding bottleneck in operational satellite NO2 retrievals. In this work, we instead use neural network (NN) models trained from over 360,000 radiative transfer (RT) simulations to translate satellite radiances across 390-495 nm to total NO2 vertical column (NO2C). Despite the wide variability of the many input parameters in the RT simulations, only a small number of key variables were found essential to the accurate prediction of NO2C, including observing angles, surface reflectivity and altitude, and several key principal component scores of the radiances. In addition to the NO2C, the NN training and cross-validation experiments show that the wider retrieval window allows some information about the vertical distribution to be retrieved (e.g., extending the rightmost wavelength from 465 to 495 nm decreases the root-mean-square-error by 0.75%) under high-NO2C conditions. Applying to four months of TROPOMI data, the trained NN model shows strong ability to reproduce the NO2C observed by the ground-based Pandonia Global Network. The coefficient of determination (R2, 0.75) and normalized mean bias (NMB, -33%) are competitive with the level 2 operational TROPOMI product (R2=0.77, NMB=−29%) over clear (geometric cloud fraction
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- 2022
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3. Brain gamma-aminobutyric acid, but not glutamine and glutamate levels are lower in older adults with chronic musculoskeletal pain: considerations by sex and brain location
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Yenisel Cruz-Almeida, Megan Forbes, Ronald C. Cohen, Adam J. Woods, Roger B. Fillingim, Joseph L. Riley, III, and Eric S. Porges
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Anesthesiology ,RD78.3-87.3 - Abstract
Abstract. Introduction and Objectives:. GABAergic and glutamatergic neurotransmitter systems are central to the pathophysiology of chronic pain and are equally affected by aging processes. We measured levels of frontal gamma-aminobutyric acid (GABA) and the combined resonance of glutamate and glutamine (Glx) in vivo using proton magnetic resonance spectroscopy (1H-MRS) to elucidate age-specific and pain-specific associations with clinical and experimental pain in older adults. Methods:. Younger (18–24, n = 24) and older (60–94, n = 41) individuals part of a larger study (Neuromodulatory Examination of Pain and Mobility Across the Lifespan [NEPAL]) underwent questionnaires, quantitative sensory testing, and 1H-MRS Mescher-Garwood point-resolved spectroscopy to measure GABA and Glx levels in prefrontal and sensorimotor brain regions. Results:. Older participants had significantly lower sensorimotor, but not prefrontal, GABA and Glx levels, compared with younger controls (P's < 0.05). Younger controls had significantly higher prefrontal and sensorimotor GABA, but not Glx, levels compared with older controls and older adults with chronic pain (P's < 0.05). Older males with chronic pain had significantly lower prefrontal GABA compared with older and younger male controls (P's < 0.05). Prefrontal GABA, but not Glx, was significantly associated with self-reported and experimental pain measures (P's < 0.05). Our results are the first to focus exclusively on age and pain differences in GABA and Glx including younger and older controls to elucidate aging and pain contributions to brain GABAergic and glutamatergic processes. Conclusion:. Evaluation of both the neuroinhibitory and neuroexcitatory mechanisms provide promising potential for improving both our understanding of the mechanisms of chronic pain in aging and opportunities for effective, individualized treatments.
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- 2021
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4. Improved Satellite Retrieval of Tropospheric NO2 Column Density via Updating of Air Mass Factor (AMF): Case Study of Southern China
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Hugo Wai Leung Mak, Joshua L. Laughner, Jimmy Chi Hung Fung, Qindan Zhu, and Ronald C. Cohen
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remote sensing techniques ,tropospheric NO2 column retrieval ,Air Mass Factor (AMF) ,meteorological reformulation ,MAX-DOAS measurements ,satellite informatics ,Science - Abstract
Improving air quality and reducing human exposure to unhealthy levels of airborne chemicals are important global missions, particularly in China. Satellite remote sensing offers a powerful tool to examine regional trends in NO2, thus providing a direct measure of key parameters that strongly affect surface air quality. To accurately resolve spatial gradients in NO2 concentration using satellite observations and thus understand local and regional aspects of air quality, a priori input data at sufficiently high spatial and temporal resolution to account for pixel-to-pixel variability in the characteristics of the land and atmosphere are required. In this paper, we adapt the Berkeley High Resolution product (BEHR-HK) and meteorological outputs from the Weather Research and Forecasting (WRF) model to describe column NO2 in southern China. The BEHR approach is particularly useful for places with large spatial variabilities and terrain height differences such as China. There are two major objectives and goals: (1) developing new BEHR-HK v3.0C product for retrieving tropospheric NO2 vertical column density (TVCD) within part of southern China, for four months of 2015, based upon satellite datasets from Ozone Monitoring Instrument (OMI); and (2) evaluating BEHR-HK v3.0C retrieval result through validation, by comparing with MAX-DOAS tropospheric column measurements conducted in Guangzhou. Results show that all BEHR-HK retrieval algorithms (with R-value of 0.9839 for v3.0C) are of higher consistency with MAX-DOAS measurements than OMI-NASA retrieval (with R-value of 0.7644). This opens new windows into research questions that require high spatial resolution, for example retrieving NO2 vertical column and ground pollutant concentration in China and other countries.
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- 2018
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5. Measurements of Atmosphere–Biosphere Exchange of Oxidized Nitrogen and Implications for the Chemistry of Atmospheric NOx
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Erin R. Delaria and Ronald C. Cohen
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- 2023
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6. Estimate of OH trends over one decade in North American cities
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Qindan Zhu, Joshua L. Laughner, and Ronald C. Cohen
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- 2022
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7. Photochemical Evolution of the 2013 California Rim Fire: Synergistic Impacts of Reactive Hydrocarbons and Enhanced Oxidants
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Glenn M Wolfe, Thomas F Hanisco, Heather L Arkinson, Donald R Blake, Armin Wisthaler, Tomas Mikoviny, Thomas B Ryerson, Ilana Pollack, Jeff Peischl, Paul O Wennberg, John D Crounse, Jason M St Clair, Alex Teng, L Greg Huey, Xiaoxi Liu, Alan Fried, Petter Weibring, Dirk Richter, James Walega, Samuel R Hall, Kirk Ullmann, Jose L Jimenez, Pedro Campuzano-Jost, T Paul Bui, Glenn Diskin, James R Podolske, Glen Sachse, and Ronald C Cohen
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Environment Pollution - Abstract
Large wildfires markedly alter regional atmospheric composition, but chemical complexity challenges model predictions of downwind impacts. Here, we elucidate key facets of 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 (VOC), oxidants, and reactive nitrogen over 12 hours of atmospheric aging. Measurements show rapid formation of ozone and peroxyacyl nitrates (PNs), sustained peroxide production, and prolonged enhancements in oxygenated VOC and nitrogen oxides (NOX). Measurements and Lagrangian trajectories constrain a 0-D puff model that approximates plume photochemical history and provides a framework for evaluating key processes. Simulations examine the effects of 1) previously-unmeasured reactive VOC identified in recent laboratory studies, and 2) emissions and secondary production of nitrous acid (HONO). Inclusion of estimated unmeasured VOC 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 two different HONO production mechanisms (particulate nitrate photolysis and heterogeneous NO2 conversion) exhibit markedly different effects on ozone, NOX, and PNs. Analysis of radical initiation rates suggests that oxygenated VOC photolysis is a major radical source, exceeding HONO photolysis when averaged over the first 2 hours 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.
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- 2022
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8. Comparison of Airborne Reactive Nitrogen Measurements During WINTER
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Tamara L. Sparks, Carlena J. Ebben, Paul J. Wooldridge, Felipe D. Lopez‐Hilfiker, Ben H. Lee, Joel A. Thornton, Erin E. McDuffie, Dorothy L. Fibiger, Steven S. Brown, Denise D. Montzka, Andrew J. Weinheimer, Jason C. Schroder, Pedro Campuzano‐Jost, Jose L. Jimenez, and Ronald C. Cohen
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- 2019
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9. Evaluation of version 3.0B of the BEHR OMI NO2 product
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Joshua L. Laughner, Qindan Zhu, and Ronald C. Cohen
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- 2019
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10. The Berkeley High Resolution Tropospheric NO2 product
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Joshua L. Laughner, Qindan Zhu, and Ronald C. Cohen
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- 2018
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11. Supplementary material to 'Volatile organic compound fluxes in the San Joaquin Valley – spatial distribution, source attribution, and inventory comparison'
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Eva Y. Pfannerstill, Caleb Arata, Qindan Zhu, Benjamin C. Schulze, Roy Woods, John H. Seinfeld, Anthony Bucholtz, Ronald C. Cohen, and Allen H. Goldstein
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- 2023
12. Volatile organic compound fluxes in the San Joaquin Valley – spatial distribution, source attribution, and inventory comparison
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Eva Y. Pfannerstill, Caleb Arata, Qindan Zhu, Benjamin C. Schulze, Roy Woods, John H. Seinfeld, Anthony Bucholtz, Ronald C. Cohen, and Allen H. Goldstein
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The San Joaquin Valley is an agricultural region in California that suffers from poor air quality. Since traffic emissions are decreasing, other sources of volatile organic compounds (VOCs) are gaining importance in the formation of secondary air pollutants. Using airborne eddy covariance, we conducted direct, spatially resolved flux observations of a wide range of VOCs in the San Joaquin Valley during June 2021 at 23–36 °C. Through landcover-informed footprint disaggregation, we were able to attribute emissions to sources and identify tracers for distinct source types. VOC mass fluxes were dominated by alcohols, mainly from dairy farms, while oak isoprene and citrus monoterpenes were important sources of reactivity. Comparisons with two commonly used inventories showed that isoprene emissions in the croplands were overestimated, while dairy and highway VOC emissions were generally underestimated in the inventories, and important citrus and biofuel VOC point sources were missing from the inventories. This study thus presents unprecedented insights into the VOC sources in an intensive agricultural region and provides much needed information for the improvement of inventories, air quality predictions and regulations.
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- 2023
13. Evidence of Nighttime Production of Organic Nitrates During SEAC4RS, FRAPPÉ, and KORUS‐AQ
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Hannah S. Kenagy, Tamara L. Sparks, Paul J. Wooldridge, Andrew J. Weinheimer, Thomas B. Ryerson, Donald R. Blake, Rebecca S. Hornbrook, Eric C. Apel, and Ronald C. Cohen
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- 2020
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14. Assessment of NO2 Observations During DISCOVER-AQ and KORUS-AQ Field Campaigns
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Sungyeon Choi, Lok N Lamsal, Melanie Folette-Cook, Joanna Joiner, Nickolay A Krotkov, William H Swartz, Kenneth E Pickering, Christopher P Loughner, Wyat Appel, Gabriele Pfister, Pablo E Saide, Ronald C. Cohen, Andrew J. Weinheimer, and Jay R Herman
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Earth Resources And Remote Sensing - Abstract
NASA’s Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ, conducted in 2011–2014) campaign in the United States and the joint NASA and National Institute of Environmental Research (NIER) Korea–United States Air Quality Study (KORUS-AQ, conducted in 2016) in South Korea were two field study programs that provided comprehensive, integrated data sets of airborne and surface observations of atmospheric constituents, including nitrogen dioxide (NO2), with the goal of improving the interpretation of spaceborne remote sensing data. Various types of NO2 measurements were made, including in situ concentrations and column amounts of NO2 using ground- and aircraft-based instruments, while NO2 column amounts were being derived from the Ozone Monitoring Instrument (OMI) on the Aura satellite. This study takes advantage of these unique datasets by first evaluating in situ data taken from two different instruments on the same aircraft platform, comparing coincidently sampled profile-integrated columns from aircraft spirals with remotely sensed column observations from ground-based Pandora spectrometers, intercomparing column observations from the ground (Pandora), aircraft (in situ vertical spirals), and space (OMI), and evaluating NO2 simulations from coarse Global Modeling Initiative (GMI) and high-resolution regional models. We then use these data to interpret observed discrepancies due to differences in sampling and deficiencies in the data reduction process. Finally, we assess satellite retrieval sensitivity to observed and modeled a priori NO2 profiles. Contemporaneous measurements from two aircraft instruments that likely sample similar air masses generally agree very well but are also found to differ in integrated columns by up to 31.9 %. These show even larger differences with Pandora, reaching up to 53.9 %, potentially due to a combination of strong gradients in NO2 fields that could be missed by aircraft spirals and errors in the Pandora retrievals. OMI NO2 values are about a actor of 2 lower in these highly polluted environments due in part to inaccurate retrieval assumptions (e.g., a priori pro-files) but mostly to OMI’s large footprint (>312 km2).
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- 2020
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15. A comprehensive organic nitrate chemistry: insights into the lifetime of atmospheric organic nitrates
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Azimeh Zare, Paul S. Romer, Tran Nguyen, Frank N. Keutsch, Kate Skog, and Ronald C. Cohen
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- 2018
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16. Observing local CO2 sources using low-cost, near-surface urban monitors
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Alexis A. Shusterman, Jinsol Kim, Kaitlyn J. Lieschke, Catherine Newman, Paul J. Wooldridge, and Ronald C. Cohen
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- 2018
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17. Modulation of hydroxyl variability by ENSO in the absence of external forcing
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Alexander J. Turner, Inez Fung, Vaishali Naik, Larry W. Horowitz, and Ronald C. Cohen
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- 2018
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18. Characterizing CO and NOy Sources and Relative Ambient Ratios in the Baltimore Area Using Ambient Measurements and Source Attribution Modeling
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Heather Simon, Luke C. Valin, Kirk R. Baker, Barron H. Henderson, James H. Crawford, Sally E. Pusede, James T. Kelly, Kristen M. Foley, R. Chris Owen, Ronald C. Cohen, Brian Timin, Andrew J. Weinheimer, Norm Possiel, Chris Misenis, Glenn S. Diskin, and Alan Fried
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- 2018
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19. Quantification of the effect of modeled lightning NO2 on UV–visible air mass factors
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Joshua L. Laughner and Ronald C. Cohen
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- 2017
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20. Supplementary material to 'Measurement report: Airborne measurements of NOx fluxes over Los Angeles during the RECAP-CA 2021 campaign'
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Clara M. Nussbaumer, Bryan K. Place, Qindan Zhu, Eva Y. Pfannerstill, Paul Wooldridge, Benjamin C. Schulze, Caleb Arata, Ryan Ward, Anthony Bucholtz, John H. Seinfeld, Allen H. Goldstein, and Ronald C. Cohen
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- 2023
21. Measurement report: Airborne measurements of NOx fluxes over Los Angeles during the RECAP-CA 2021 campaign
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Clara M. Nussbaumer, Bryan K. Place, Qindan Zhu, Eva Y. Pfannerstill, Paul Wooldridge, Benjamin C. Schulze, Caleb Arata, Ryan Ward, Anthony Bucholtz, John H. Seinfeld, Allen H. Goldstein, and Ronald C. Cohen
- Abstract
Nitrogen oxides (NOx ≡ NO + NO2) are involved in most atmospheric photochemistry, including the formation of tropospheric ozone (O3). While various methods exist to accurately measure NOx concentrations, it is still a challenge to quantify the source and flux of NOx emissions. We present airborne measurements of NOx and winds used to infer the emission of NOx across Los Angeles. The measurements were obtained during the research aircraft campaign RECAP-CA (Re-Evaluating the Chemistry of Air Pollutants in CAlifornia) in June 2021. Geographic allocations of the fluxes are compared to the NOx emission inventory from the California Air Resources Board (CARB). We find that the NOx fluxes have a pronounced weekend effect and are highest in the Eastern part of the San Bernardino valley. The comparison of the RECAP-CA and the modeled CARB NOx fluxes suggest the modeled emissions are too high near the coast and in downtown Los Angeles and too low further inland in the Eastern part of the San Bernardino valley.
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- 2023
22. Variable effects of spatial resolution on modeling of nitrogen oxides
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Chi Li, Randall V. Martin, Ronald C. Cohen, Liam Bindle, Dandan Zhang, Deepangsu Chatterjee, Hongjian Weng, and Jintai Lin
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Atmospheric Science - Abstract
The lifetime and concentration of nitrogen oxides (NOx) are susceptible to nonlinear production and loss and to the resolution of a chemical transport model (CTM). This is due to the strong spatial gradients of NOx and the dependence of its own chemical loss on such gradients. In this study, we use the GEOS-Chem CTM in its high-performance implementation (GCHP) to investigate NOx simulations over the eastern United States across a wide range of spatial model resolutions (six different horizontal grids from 13 to 181 km). Following increasing grid size, afternoon surface NOx mixing ratios over July 2015 generally decrease over the Great Lakes region (GL) and increase over the southern states of the US region (SS), yielding regional differences (181 km vs. 13 km) of −16 % (in the GL) to 7 % (in the SS); meanwhile, hydrogen oxide radicals (HOx) increase over both regions, consistent with their different chemical regimes (i.e., NOx-saturated in the GL and NOx-limited in the SS). Nighttime titration of ozone by surface nitric oxide (NO) was found to be more efficient at coarser resolutions, leading to longer NOx lifetimes and higher surface mixing ratios of nitrogen dioxide (NO2) over the GL in January 2015. The tropospheric NO2 column density at typical afternoon satellite overpass time has spatially more coherent negative biases (e.g., −8 % over the GL) at coarser resolutions in July, which reversed the positive biases of surface NOx over the SS. The reduced NOx aloft (>1 km altitude) at coarser resolutions was attributable to the enhanced HOx that intrudes into the upper troposphere. Application of coarse-resolution simulations for interpreting satellite NO2 columns will generally underestimate surface NO2 over the GL and overestimate surface NO2 over the SS in summer, but it will uniformly overestimate NOx emissions over both regions. This study significantly broadens understanding of factors contributing to NOx resolution effects and the role of fine-resolution data in accurately simulating and interpreting NOx and its relevance to air quality.
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- 2023
23. Supplementary material to 'Direct observations of NOx emissions over the San Joaquin Valley using airborne flux measurements during RECAP-CA 2021 field campaign'
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Qindan Zhu, Bryan Place, Eva Y. Pfannerstill, Sha Tong, Huanxin Zhang, Jun Wang, Clara M. Nussbaumer, Paul Wooldridge, Benjamin C. Schulze, Caleb Arata, Anthony Bucholtz, John H. Seinfeld, Allen H. Goldstein, and Ronald C. Cohen
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- 2023
24. Direct observations of NOx emissions over the San Joaquin Valley using airborne flux measurements during RECAP-CA 2021 field campaign
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Qindan Zhu, Bryan Place, Eva Y. Pfannerstill, Sha Tong, Huanxin Zhang, Jun Wang, Clara M. Nussbaumer, Paul Wooldridge, Benjamin C. Schulze, Caleb Arata, Anthony Bucholtz, John H. Seinfeld, Allen H. Goldstein, and Ronald C. Cohen
- Abstract
Nitrogen oxides (NOx) are principle components of air pollution and serve as important ozone precursors. As the San Joaquin Valley (SJV) experiences some of the worst air quality in the United States, reducing NOx emissions is a pressing need, yet quantifying current emissions is complicated due to a mixture of mobile and agriculture sources. We performed airborne eddy covariance flux measurements during the Re-Evaluating the Chemistry of Air Pollutants in CAlifornia (RECAP-CA) field campaign in June 2021. Combining footprint calculations and land cover statistics, we disaggregate the observed fluxes into component fluxes characterized by three different land cover types. On average we find emissions of 2.95 mg m-2 h-1 over highways, 1.24 mg m-2 h-1 over urban areas and 0.79 mg m-2 h-1 over croplands. The calculated NOx emissions using flux observations are utilized to evaluate anthropogenic emission inventories and soil NOx emission schemes. We show that two anthropogenic inventories for mobile sources, EMFAC (EMssion FACtor) and FIVE (Fuel-based Inventory for Vehicle Emissions), yield similar agreement with emissions derived from measured fluxes over urban regions with 24 % and 22 % low bias, respectively. Three soil NOx schemes, including MEGAN v3 (Model of Emissions of Gases and Aerosols from Nature), BEIS v3.14 (Biogenic Emission Inventory System) and BDISNP (Berkeley Dalhousie Iowa Soil NO Parameterization), show substantial underestimates over the study domain. Compared to the cultivated soil NOx emissions derived from measured fluxes, MEGAN and BEIS are lower by more than one order of magnitude and BDISNP is lower by a factor of 2.7. Despite the low bias, observed soil NOx emissions and BDISNP present a similar spatial pattern as well as temperature dependence. We conclude that soil NOx is a key feature of the NOx emissions in the SJV and that a state-of-the-science model of these emissions is needed to simulate emissions for modeling air quality in the region.
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- 2023
25. Characterization of errors in satellite-based HCHO ∕ NO2 tropospheric column ratios with respect to chemistry, column-to-PBL translation, spatial representation, and retrieval uncertainties
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Amir H. Souri, Matthew S. Johnson, Glenn M. Wolfe, James H. Crawford, Alan Fried, Armin Wisthaler, William H. Brune, Donald R. Blake, Andrew J. Weinheimer, Tijl Verhoelst, Steven Compernolle, Gaia Pinardi, Corinne Vigouroux, Bavo Langerock, Sungyeon Choi, Lok Lamsal, Lei Zhu, Shuai Sun, Ronald C. Cohen, Kyung-Eun Min, Changmin Cho, Sajeev Philip, Xiong Liu, and Kelly Chance
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Atmospheric Science - Abstract
The availability of formaldehyde (HCHO) (a proxy for volatile organic compound reactivity) and nitrogen dioxide (NO2) (a proxy for nitrogen oxides) tropospheric columns from ultraviolet–visible (UV–Vis) satellites has motivated many to use their ratios to gain some insights into the near-surface ozone sensitivity. Strong emphasis has been placed on the challenges that come with transforming what is being observed in the tropospheric column to what is actually in the planetary boundary layer (PBL) and near the surface; however, little attention has been paid to other sources of error such as chemistry, spatial representation, and retrieval uncertainties. Here we leverage a wide spectrum of tools and data to quantify those errors carefully. Concerning the chemistry error, a well-characterized box model constrained by more than 500 h of aircraft data from NASA's air quality campaigns is used to simulate the ratio of the chemical loss of HO2 + RO2 (LROx) to the chemical loss of NOx (LNOx). Subsequently, we challenge the predictive power of HCHO/NO2 ratios (FNRs), which are commonly applied in current research, in detecting the underlying ozone regimes by comparing them to LROx/LNOx. FNRs show a strongly linear (R2=0.94) relationship with LROx/LNOx, but only on the logarithmic scale. Following the baseline (i.e., ln(LROx/LNOx) = −1.0 ± 0.2) with the model and mechanism (CB06, r2) used for segregating NOx-sensitive from VOC-sensitive regimes, we observe a broad range of FNR thresholds ranging from 1 to 4. The transitioning ratios strictly follow a Gaussian distribution with a mean and standard deviation of 1.8 and 0.4, respectively. This implies that the FNR has an inherent 20 % standard error (1σ) resulting from not accurately describing the ROx–HOx cycle. We calculate high ozone production rates (PO3) dominated by large HCHO × NO2 concentration levels, a new proxy for the abundance of ozone precursors. The relationship between PO3 and HCHO × NO2 becomes more pronounced when moving towards NOx-sensitive regions due to nonlinear chemistry; our results indicate that there is fruitful information in the HCHO × NO2 metric that has not been utilized in ozone studies. The vast amount of vertical information on HCHO and NO2 concentrations from the air quality campaigns enables us to parameterize the vertical shapes of FNRs using a second-order rational function permitting an analytical solution for an altitude adjustment factor to partition the tropospheric columns into the PBL region. We propose a mathematical solution to the spatial representation error based on modeling isotropic semivariograms. Based on summertime-averaged data, the Ozone Monitoring Instrument (OMI) loses 12 % of its spatial information at its native resolution with respect to a high-resolution sensor like the TROPOspheric Monitoring Instrument (TROPOMI) (> 5.5 × 3.5 km2). A pixel with a grid size of 216 km2 fails at capturing ∼ 65 % of the spatial information in FNRs at a 50 km length scale comparable to the size of a large urban center (e.g., Los Angeles). We ultimately leverage a large suite of in situ and ground-based remote sensing measurements to draw the error distributions of daily TROPOMI and OMI tropospheric NO2 and HCHO columns. At a 68 % confidence interval (1σ), errors pertaining to daily TROPOMI observations, either HCHO or tropospheric NO2 columns, should be above 1.2–1.5 × 1016 molec. cm−2 to attain a 20 %–30 % standard error in the ratio. This level of error is almost non-achievable with the OMI given its large error in HCHO. The satellite column retrieval error is the largest contributor to the total error (40 %–90 %) in the FNRs. Due to a stronger signal in cities, the total relative error (< 50 %) tends to be mild, whereas areas with low vegetation and anthropogenic sources (e.g., the Rocky Mountains) are markedly uncertain (> 100 %). Our study suggests that continuing development in the retrieval algorithm and sensor design and calibration is essential to be able to advance the application of FNRs beyond a qualitative metric.
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- 2023
26. Observing Annual Trends in Vehicular CO2 Emissions
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Jinsol Kim, Alexander J. Turner, Helen L. Fitzmaurice, Erin R. Delaria, Catherine Newman, Paul J. Wooldridge, and Ronald C. Cohen
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Environmental Chemistry ,General Chemistry - Published
- 2022
27. Leaf Stomatal Uptake of Alkyl Nitrates
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Bryan K. Place, Erin R. Delaria, and Ronald C. Cohen
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Ecology ,Health, Toxicology and Mutagenesis ,Environmental Chemistry ,Pollution ,Waste Management and Disposal ,Water Science and Technology - Published
- 2022
28. Contribution of Organic Nitrates to Organic Aerosol over South Korea during KORUS-AQ
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Hannah S. Kenagy, Paul S. Romer Present, Paul J. Wooldridge, Benjamin A. Nault, Pedro Campuzano-Jost, Douglas A. Day, Jose L. Jimenez, Azimeh Zare, Havala O.T. Pye, Jinhyeok Yu, Chul H. Song, Donald R. Blake, Jung-Hun Woo, Younha Kim, and Ronald C. Cohen
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particulate matter ,Aerosols ,organic nitrates ,Air Pollutants ,Volatile Organic Compounds ,absorptive partitioning theory ,Nitrates ,General Chemistry ,Article ,nitrogen oxides ,urban air quality ,Environmental Chemistry ,Cities ,organic aerosol ,Environmental Sciences - Abstract
The role of anthropogenic NOx emissions in secondary organic aerosol (SOA) production is not fully understood but is important for understanding the contribution of emissions to air quality. Here, we examine the role of organic nitrates (RONO2) in SOA formation over the Korean Peninsula during the Korea-United States Air Quality field study in Spring 2016 as a model for RONO2 aerosol in cities worldwide. We use aircraft-based measurements of the particle phase and total (gas + particle) RONO2 to explore RONO2 phase partitioning. These measurements show that, on average, one-fourth of RONO2 are in the condensed phase, and we estimate that ≈15% of the organic aerosol (OA) mass can be attributed to RONO2. Furthermore, we observe that the fraction of RONO2 in the condensed phase increases with OA concentration, evidencing that equilibrium absorptive partitioning controls the RONO2 phase distribution. Lastly, we model RONO2 chemistry and phase partitioning in the Community Multiscale Air Quality modeling system. We find that known chemistry can account for one-third of the observed RONO2, but there is a large missing source of semivolatile, anthropogenically derived RONO2. We propose that this missing source may result from the oxidation of semi- and intermediate-volatility organic compounds and/or from anthropogenic molecules that undergo autoxidation or multiple generations of OH-initiated oxidation.
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- 2021
29. Supplementary material to 'Variable effects of spatial resolution on modeling of nitrogen oxides'
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Chi Li, Randall V. Martin, Ronald C. Cohen, Liam Bindle, Dandan Zhang, Deepangsu Chatterjee, Hongjian Weng, and Jintai Lin
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- 2022
30. ClNO2 Yields From Aircraft Measurements During the 2015 WINTER Campaign and Critical Evaluation of the Current Parameterization
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Erin E. McDuffie, Dorothy L. Fibiger, William P. Dubé, Felipe Lopez Hilfiker, Ben H. Lee, Lyatt Jaeglé, Hongyu Guo, Rodney J. Weber, J. Michael Reeves, Andrew J. Weinheimer, Jason C. Schroder, Pedro Campuzano‐Jost, Jose L. Jimenez, Jack E. Dibb, Patrick Veres, Carlena Ebben, Tamara L. Sparks, Paul J. Wooldridge, Ronald C. Cohen, Teresa Campos, Samuel R. Hall, Kirk Ullmann, James M. Roberts, Joel A. Thornton, and Steven S. Brown
- Published
- 2018
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31. Direct estimates of biomass burning NOx emissions and lifetimes using daily observations from TROPOMI
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Xiaomeng Jin, Ronald C. Cohen, and Qindan Zhu
- Subjects
Atmosphere ,Troposphere ,Atmospheric Science ,Reactive nitrogen ,Satellite remote sensing ,Radiative transfer ,Moderate-resolution imaging spectroradiometer ,Atmospheric sciences ,Biomass burning ,Global model - Abstract
Biomass burning emits an estimated 25 % of global annual nitrogen oxides (NOx), an important constituent that participates in the oxidative chemistry of the atmosphere. Estimates of NOx emission factors, representing the amount of NOx per mass burned, are primarily based on field or laboratory case studies, but the sporadic and transient nature of wildfires makes it challenging to verify whether these case studies represent the behavior of the global fires that occur on earth. Satellite remote sensing provides a unique view of the earth, allowing for the study of emissions and downwind evolution of NOx from a large number of fires. We describe direct estimates of NOx emissions and lifetimes for fires using an exponentially modified Gaussian analysis of daily TROPOspheric Monitoring Instrument (TROPOMI) retrievals of NO2 tropospheric columns. We update the a priori profile of NO2 with a fine-resolution (0.25∘) global model simulation from NASA's GEOS Composition Forecasting System (GEOS-CF), which largely enhances NO2 columns over fire plumes. We derive representative NOx emission factors for six fuel types globally by linking TROPOMI-derived NOx emissions with observations of fire radiative power from Moderate Resolution Imaging Spectroradiometer (MODIS). Satellite-derived NOx emission factors are largely consistent with those derived from in situ measurements. We observe decreasing NOx lifetime with fire emissions, which we infer is due to the increase in both NOx abundance and hydroxyl radical production. Our findings suggest promise for applying space-based observations to track the emissions and chemical evolution of reactive nitrogen from wildfires.
- Published
- 2021
32. The Berkeley Environmental Air-quality and CO2 Network: field calibrations of sensor temperature dependence and assessment of network scale CO2 accuracy
- Author
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Catherine Newman, Paul J. Wooldridge, Ronald C. Cohen, Helen Fitzmaurice, Jinsol Kim, K. A. Worthington, and Erin R. Delaria
- Subjects
Atmospheric Science ,Offset (computer science) ,Software deployment ,Line (geometry) ,Environmental science ,Point (geometry) ,Tracking (particle physics) ,Scale (map) ,Air quality index ,Field (geography) ,Remote sensing - Abstract
The majority of global anthropogenic CO2 emissions originate in cities. We have proposed that dense networks are a strategy for tracking changes to the processes contributing to urban CO2 emissions and suggested that a network with ∼ 2 km measurement spacing and ∼ 1 ppm node-to-node precision would be effective at constraining point, line, and area sources within cities. Here, we report on an assessment of the accuracy of the Berkeley Environmental Air-quality and CO2 Network (BEACO2N) CO2 measurements over several years of deployment. We describe a new procedure for improving network accuracy that accounts for and corrects the temperature-dependent zero offset of the Vaisala CarboCap GMP343 CO2 sensors used. With this correction we show that a total error of 1.6 ppm or less can be achieved for networks that have a calibrated reference location and 3.6 ppm for networks without a calibrated reference.
- Published
- 2021
33. Supplementary material to 'Characterization of Errors in Satellite-based HCHO / NO2 Tropospheric Column Ratios with Respect to Chemistry, Column to PBL Translation, Spatial Representation, and Retrieval Uncertainties'
- Author
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Amir H. Souri, Matthew S. Johnson, Glenn M. Wolfe, James H. Crawford, Alan Fried, Armin Wisthaler, William H. Brune, Donald R. Blake, Andrew J. Weinheimer, Tijl Verhoelst, Steven Compernolle, Gaia Pinardi, Corinne Vigouroux, Bavo Langerock, Sungyeon Choi, Lok Lamsal, Lei Zhu, Shuai Sun, Ronald C. Cohen, Kyung-Eun Min, Changmin Cho, Sajeev Philip, Xiong Liu, and Kelly Chance
- Published
- 2022
34. Characterization of Errors in Satellite-based HCHO / NO2 Tropospheric Column Ratios with Respect to Chemistry, Column to PBL Translation, Spatial Representation, and Retrieval Uncertainties
- Author
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Amir H. Souri, Matthew S. Johnson, Glenn M. Wolfe, James H. Crawford, Alan Fried, Armin Wisthaler, William H. Brune, Donald R. Blake, Andrew J. Weinheimer, Tijl Verhoelst, Steven Compernolle, Gaia Pinardi, Corinne Vigouroux, Bavo Langerock, Sungyeon Choi, Lok Lamsal, Lei Zhu, Shuai Sun, Ronald C. Cohen, Kyung-Eun Min, Changmin Cho, Sajeev Philip, Xiong Liu, and Kelly Chance
- Abstract
The availability of formaldehyde (HCHO) (a proxy for volatile organic compound reactivity) and nitrogen dioxide (NO2) (a proxy for nitrogen oxides) tropospheric columns from Ultraviolet-Visible (UV-Vis) satellites has motivated many to use their ratios to gain some insights into the near-surface ozone sensitivity. Strong emphasis has been placed on the challenges that come with transforming what is being observed in the tropospheric column to what is actually in the planetary boundary layer (PBL) and near to the surface; however, little attention has been paid to other sources of error such as chemistry, spatial representation, and retrieval uncertainties. Here we leverage a wide spectrum of tools and data to carefully quantify those errors. Concerning the chemistry error, a well-characterized box model constrained by more than 500 hours of aircraft data from NASA’s air quality campaigns is used to simulate the ratio of the chemical loss of HO2+RO2 (LROx) to the chemical loss of NOx (LNOx). Subsequently, we challenge the predictive power of HCHO / NO2 ratios (FNRs), which are commonly applied in current research, at detecting the underlying ozone regimes by comparing them to LROx / LNOx. FNRs show a strongly linear (R2=0.94) relationship to LROx / LNOx in the log-log scale. Following the baseline (i.e., ln(LROx / LNOx) = -1.0±0.2) with the model and mechanism (CB06, r2) used for segregating NOx-sensitive from VOC-sensitive regimes, we observe a broad range of FNR thresholds ranging from 1 to 4. The transitioning ratios strictly follow a Gaussian distribution with a mean and standard deviation of 1.8 and 0.4, respectively. This implies that FNR has an inherent 20 % standard error (1-sigma) resulting from not being able to fully describe the ROx-HOx cycle. We calculate high ozone production rates (PO3) dominated by large HCHO×NO2 concentration levels, a new proxy for the abundance of ozone precursors. The relationship between PO3 and HCHO×NO2 becomes more pronounced when moving towards NOx-sensitive regions due to non-linear chemistry; our results indicate that there is fruitful information in the HCHO×NO2 metric that has not been utilized in ozone studies. The vast amount of vertical information on HCHO and NO2 concentration from the air quality campaigns enables us to parameterize the vertical shapes of FNRs using a second-order rational function permitting an analytical solution for an altitude adjustment factor to partition the tropospheric columns to the PBL region. We propose a mathematical solution to the spatial representation error based on modeling isotropic semivariograms. With respect to a high-resolution sensor like TROPOspheric Monitoring Instrument (TROPOMI) (>5.5×3.5 km2), Ozone Monitoring Instrument (OMI) loses 12 % of spatial information at its native resolution. A pixel with a grid size of 216 km2 fails at capturing ~65 % of the spatial information in FNRs at a 50 km length scale comparable to the size of a large urban center (e.g., Los Angeles). We ultimately leverage a large suite of in-situ and ground-based remote sensing measurements to draw the error distributions of daily TROPOMI and OMI tropospheric NO2 and HCHO columns. At 68 % confidence interval (1 sigma) errors pertaining to daily TROPOMI observations, either HCHO or tropospheric NO2 columns should be above 1.2–1.5×1016 molec.cm-2 to attain 20–30 % standard error in the ratio. This level of error is almost non-achievable with OMI given its large error in HCHO. The satellite column retrieval error is the largest contributor to the total error (40–90 %) in the FNRs. Due to a stronger signal in cities, the total relative error (100 %). Our study suggests that continuing development in the retrieval algorithm and sensor design and calibration is essential to be able to advance the application of FNRs beyond a qualitative metric.
- Published
- 2022
35. Characterizing CO and NO
- Author
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Heather, Simon, Luke C, Valin, Kirk R, Baker, Barron H, Henderson, James H, Crawford, Sally E, Pusede, James T, Kelly, Kristen M, Foley, R Chris, Owen, Ronald C, Cohen, Brian, Timin, Andrew J, Weinheimer, Norm, Possiel, Chris, Misenis, Glenn S, Diskin, and Alan, Fried
- Abstract
Modeled source attribution information from the Community Multiscale Air Quality model was coupled with ambient data from the 2011 Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality Baltimore field study. We assess source contributions and evaluate the utility of using aircraft measured CO and NO
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- 2022
36. Thoughts on air quality when the world is electrified
- Author
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Ronald C, Cohen
- Subjects
Multidisciplinary - Published
- 2022
37. Organic nitrate chemistry and its implications for nitrogen budgets in an isoprene- and monoterpene-rich atmosphere: constraints from aircraft (SEAC4RS) and ground-based (SOAS) observations in the Southeast US
- Author
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Jenny A. Fisher, Daniel J. Jacob, Katherine R. Travis, Patrick S. Kim, Eloise A. Marais, Christopher Chan Miller, Karen Yu, Lei Zhu, Robert M. Yantosca, Melissa P. Sulprizio, Jingqiu Mao, Paul O. Wennberg, John D. Crounse, Alex P. Teng, Tran B. Nguyen, Jason M. St. Clair, Ronald C. Cohen, Paul Romer, Benjamin A. Nault, Paul J. Wooldridge, Jose L. Jimenez, Pedro Campuzano-Jost, Douglas A. Day, Weiwei Hu, Paul B. Shepson, Fulizi Xiong, Donald R. Blake, Allen H. Goldstein, Pawel K. Misztal, Thomas F. Hanisco, Glenn M. Wolfe, Thomas B. Ryerson, Armin Wisthaler, and Tomas Mikoviny
- Published
- 2016
- Full Text
- View/download PDF
38. The potential for geostationary remote sensing of NO2 to improve weather prediction
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Jeffrey L. Anderson, Ronald C. Cohen, Inez Fung, Xueling Liu, and Arthur P. Mizzi
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,Planetary boundary layer ,010501 environmental sciences ,01 natural sciences ,Boundary layer ,Data assimilation ,Remote sensing (archaeology) ,Weather prediction ,Geostationary orbit ,Environmental science ,Air quality index ,Mixing (physics) ,0105 earth and related environmental sciences ,Remote sensing - Abstract
Observations of winds in the planetary boundary layer remain sparse making it challenging to simulate and predict atmospheric conditions that are most important for describing and predicting urban air quality. Short-lived chemicals are observed as plumes whose location is affected by boundary layer winds and whose lifetime is affected by boundary layer height and mixing. Here we investigate the application of data assimilation of NO2 columns as will be observed from geostationary orbit to improve predictions and retrospective analysis of wind fields in the boundary layer.
- Published
- 2021
39. Two Decades of Changes in Summertime Ozone Production in California's South Coast Air Basin
- Author
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Begie C. Perdigones, Soojin Lee, Ronald C. Cohen, Jeong-Hoo Park, and Kyung-Eun Min
- Subjects
Air Pollutants ,Volatile Organic Compounds ,Ozone ,Air Pollution ,Environmental Chemistry ,Humans ,General Chemistry ,California ,Environmental Monitoring - Abstract
Tropospheric ozone (O
- Published
- 2022
40. Impact of OA on the Temperature Dependence of PM 2.5 in the Los Angeles Basin
- Author
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Ronald C. Cohen and Clara M. Nussbaumer
- Subjects
BTEX ,Xylenes ,010501 environmental sciences ,Structural basin ,Atmospheric sciences ,complex mixtures ,01 natural sciences ,Ethylbenzene ,chemistry.chemical_compound ,Environmental Chemistry ,Benzene ,Air quality index ,Isoprene ,0105 earth and related environmental sciences ,Air Pollutants ,Temperature ,General Chemistry ,respiratory system ,Los Angeles ,Aerosol ,Organic fraction ,chemistry ,Environmental science ,Particulate Matter ,Environmental Monitoring ,Toluene - Abstract
Air quality policy in the Los Angeles megacity is a guidepost for other megacities. Over the last 2 decades, the policy has substantially reduced aerosol (OA) concentrations and the frequency of high aerosol events in the region. During this time, the emissions contributing to, and the temperature associated with, high aerosol events have changed. Early in the record, aerosol concentrations responded to a variety of different sources. We show that emission control has been effective with a strong decrease in temperature-independent sources. As a result, the response of aerosol to temperature has become a dominant feature of high aerosol events in the basin. The organic fraction of the aerosol (OA) increases with the temperature approaching 35% at 40 °C. We describe a simple conceptual model of aerosol in Los Angeles, illustrating how benzene, toluene, ethylbenzene, and xylenes (BTEX) and isoprene, along with molecules for which these are plausible surrogates such as monoterpenes, are sufficient to explain the observed temperature dependence of PM 2.5.
- Published
- 2021
41. The Role of Temperature and NOx in Ozone Trends in the Los Angeles Basin
- Author
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Ronald C. Cohen and Clara M. Nussbaumer
- Subjects
Ozone ,General Chemistry ,010501 environmental sciences ,Structural basin ,High ozone ,01 natural sciences ,chemistry.chemical_compound ,Megacity ,chemistry ,Environmental chemistry ,Environmental Chemistry ,Environmental science ,Nitrogen oxides ,Air quality index ,NOx ,0105 earth and related environmental sciences - Abstract
Ozone, a major contributor to poor air quality, has an array of adverse effects on human, animal, and plant health. In the Los Angeles basin, a megacity that has pursued cleaner air for decades, unhealthy levels of ozone have decreased but remain stubbornly frequent even as the ozone precursors NOx (nitrogen oxides ≡ NO2 + NO) and VOC (volatile organic compounds) have decreased. We describe a combined analysis of decadal trends in these precursors, differences in emissions with day-of-week, and of the impact of temperature to assess the role of VOC and NOx and the likely effects of additional emission reductions on the occurrence of high ozone in the region.
- Published
- 2020
42. Laboratory measurements of stomatal NO2 deposition to native California trees and the role of forests in the NOx cycle
- Author
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Amy X. Liu, Ronald C. Cohen, Bryan K. Place, and Erin R. Delaria
- Subjects
inorganic chemicals ,0106 biological sciences ,Atmospheric Science ,geography ,Daytime ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Enclosure ,respiratory system ,15. Life on land ,Atmospheric sciences ,01 natural sciences ,Sink (geography) ,Deposition rate ,Environmental science ,Ecosystem ,Tree species ,NOx ,010606 plant biology & botany ,0105 earth and related environmental sciences - Abstract
Both canopy-level field measurements and laboratory studies suggest that uptake of NO2 through the leaf stomata of vegetation is a significant sink of atmospheric NOx. However, the mechanisms of this foliar NO2 uptake and their impact on NOx lifetimes remain incompletely understood. To understand the leaf-level processes affecting ecosystem-scale atmosphere–biosphere NOx exchange, we have conducted laboratory experiments of branch-level NO2 deposition fluxes to six coniferous and four broadleaf native California trees using a branch enclosure system with direct laser-induced fluorescence (LIF) detection of NO2. We report NO2 foliar deposition that demonstrates a large degree of inter-species variability, with maximum observed deposition velocities ranging from 0.15 to 0.51 cm s−1 during the daytime, as well as significant stomatal opening during the night. We also find that the contribution of mesophyllic processing to the overall deposition rate of NO2 varies by tree species but has an ultimately inconsequential impact on NOx budgets and lifetimes. Additionally, we find no evidence of any emission of NO2 from leaves, suggesting an effective unidirectional exchange of NOx between the atmosphere and vegetation.
- Published
- 2020
43. Combining Machine Learning and Satellite Observations to Predict Spatial and Temporal Variation of near Surface OH in North American Cities
- Author
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Qindan Zhu, Joshua L. Laughner, and Ronald C. Cohen
- Subjects
Machine Learning ,Air Pollutants ,Nitrogen Dioxide ,North America ,Environmental Chemistry ,General Chemistry ,Cities ,Environmental Monitoring - Abstract
The hydroxyl radical (OH) is the primary cleansing agent in the atmosphere. The abundance of OH in cities initiates the removal of local pollutants; therefore, it serves as the key species describing the urban chemical environment. We propose a machine learning (ML) approach as an efficient alternative to OH simulation using a computationally expensive chemical transport model. The ML model is trained on the parameters simulated from the WRF-Chem model, and it suggests that six predictive parameters are capable of explaining 76% of the OH variability. The parameters are the tropospheric NO₂ column, the tropospheric HCHO column, J(O¹D), H₂O, temperature, and pressure. We then use observations of the tropospheric NO₂ column and HCHO column from OMI as input to the ML model to enable measurement-based prediction of daily near surface OH at 1:30 pm local time across 49 North American cities over the course of 10 years between 2005 and 2014. The result is validated by comparing the OH predictions to measurements of isoprene, which has a source that is uncorrelated with OH and is removed rapidly and almost exclusively by OH in the daytime. We demonstrate that the predicted OH is, as expected, anticorrelated with isoprene. We also show that this ML model is consistent with our understanding of OH chemistry given the solely data-driven nature.
- Published
- 2022
44. Leaf Stomatal Control over Acyl Peroxynitrate Dry Deposition to Trees
- Author
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Erin R. Delaria, Bryan K. Place, Ronald C. Cohen, and Amy X. Liu
- Subjects
Atmosphere ,Atmospheric Science ,chemistry.chemical_compound ,Space and Planetary Science ,Geochemistry and Petrology ,Chemistry ,Environmental chemistry ,Peroxynitrate ,NOx - Abstract
Acyl peroxynitrates are formed in the atmosphere through the oxidation of NOx and are treated as temporary NOx sinks because they typically decompose to rerelease NOx on the time scale of a few hou...
- Published
- 2020
45. Assessment of NO2 observations during DISCOVER-AQ and KORUS-AQ field campaigns
- Author
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Wyat Appel, Pablo E. Saide, Lok N. Lamsal, Andrew J. Weinheimer, Nickolay A. Krotkov, Jay R. Herman, Ronald C. Cohen, Sungyeon Choi, Melanie Follette-Cook, Joanna Joiner, William H. Swartz, Kenneth E. Pickering, Gabriele Pfister, and Christopher P. Loughner
- Subjects
Ozone Monitoring Instrument ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,Spectrometer ,Sampling (statistics) ,010501 environmental sciences ,01 natural sciences ,Column (database) ,Footprint ,Environmental science ,Satellite ,Air quality index ,0105 earth and related environmental sciences ,Remote sensing ,Data reduction - Abstract
NASA's Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ, conducted in 2011–2014) campaign in the United States and the joint NASA and National Institute of Environmental Research (NIER) Korea–United States Air Quality Study (KORUS-AQ, conducted in 2016) in South Korea were two field study programs that provided comprehensive, integrated datasets of airborne and surface observations of atmospheric constituents, including nitrogen dioxide (NO2), with the goal of improving the interpretation of spaceborne remote sensing data. Various types of NO2 measurements were made, including in situ concentrations and column amounts of NO2 using ground- and aircraft-based instruments, while NO2 column amounts were being derived from the Ozone Monitoring Instrument (OMI) on the Aura satellite. This study takes advantage of these unique datasets by first evaluating in situ data taken from two different instruments on the same aircraft platform, comparing coincidently sampled profile-integrated columns from aircraft spirals with remotely sensed column observations from ground-based Pandora spectrometers, intercomparing column observations from the ground (Pandora), aircraft (in situ vertical spirals), and space (OMI), and evaluating NO2 simulations from coarse Global Modeling Initiative (GMI) and high-resolution regional models. We then use these data to interpret observed discrepancies due to differences in sampling and deficiencies in the data reduction process. Finally, we assess satellite retrieval sensitivity to observed and modeled a priori NO2 profiles. Contemporaneous measurements from two aircraft instruments that likely sample similar air masses generally agree very well but are also found to differ in integrated columns by up to 31.9 %. These show even larger differences with Pandora, reaching up to 53.9 %, potentially due to a combination of strong gradients in NO2 fields that could be missed by aircraft spirals and errors in the Pandora retrievals. OMI NO2 values are about a factor of 2 lower in these highly polluted environments due in part to inaccurate retrieval assumptions (e.g., a priori profiles) but mostly to OMI's large footprint (>312 km2).
- Published
- 2020
46. A model-based analysis of foliar NOx deposition
- Author
-
Erin R. Delaria and Ronald C. Cohen
- Subjects
Canopy ,Atmospheric Science ,Ozone ,010504 meteorology & atmospheric sciences ,Vapour Pressure Deficit ,chemistry.chemical_element ,010501 environmental sciences ,15. Life on land ,Atmospheric sciences ,01 natural sciences ,Nitrogen ,chemistry.chemical_compound ,Water potential ,Deposition (aerosol physics) ,chemistry ,13. Climate action ,Environmental science ,Ecosystem ,NOx ,0105 earth and related environmental sciences - Abstract
Foliar deposition of NO2 removes a large fraction of the global soil-emitted NOx. Understanding the mechanisms of NOx foliar loss is important for constraining surface ozone, constraining NOx mixing ratios, and assessing the impacts of nitrogen inputs to ecosystems. We have constructed a 1-D multibox model with representations of chemistry and vertical transport to evaluate the impact of leaf-level processes on canopy-scale concentrations, lifetimes, and canopy fluxes of NOx. Our model is able to closely replicate canopy fluxes and above-canopy NOx daytime mixing ratios observed during two field campaigns, one in a western Sierra Nevada pine forest (BEARPEX-2009) and the other in a northern Michigan mixed hardwood forest (UMBS-2012). We present a conceptual argument for the importance of NO2 dry deposition and demonstrate that NO2 deposition can provide a mechanistic explanation for the canopy reduction of NOx. We show that foliar deposition can explain observations suggesting as much as ∼60 % of soil-emitted NOx is removed within forest canopies. Stomatal conductances greater than 0.1 cm s−1 result in modeled canopy reduction factors in the range of those used in global models, reconciling inferences of canopy NOx reduction with leaf-level deposition processes. We show that incorporating parameterizations for vapor pressure deficit and soil water potential has a substantial impact on predicted NO2 deposition in our model, with the percent of soil NOx removed within one canopy increasing by ∼15 % in wet conditions compared to dry conditions. NO2 foliar deposition was also found to have a significant impact on ozone and nitrogen budgets under both high- and low-NOx conditions.
- Published
- 2020
47. The changing role of organic nitrates in the removal and transport of NOx
- Author
-
Paul S. Romer Present, Ronald C. Cohen, and Azimeh Zare
- Subjects
chemistry.chemical_classification ,Atmospheric Science ,Ozone ,010504 meteorology & atmospheric sciences ,Climate system ,Air pollution ,010402 general chemistry ,medicine.disease_cause ,01 natural sciences ,0104 chemical sciences ,Organic nitrates ,chemistry.chemical_compound ,chemistry ,13. Climate action ,Environmental chemistry ,medicine ,Environmental science ,Volatile organic compound ,Nitrogen oxides ,Air quality index ,NOx ,0105 earth and related environmental sciences - Abstract
A better understanding of the chemistry of nitrogen oxides (NOx) is crucial to effectively reducing air pollution and predicting future air quality. The response of NOx lifetime to perturbations in emissions or in the climate system is set in large part by whether NOx loss occurs primarily by the direct formation of HNO3 or through the formation of alkyl and multifunctional nitrates (RONO2). Using 15 years of detailed in situ observations, we show that in the summer daytime continental boundary layer the relative importance of these two pathways can be well approximated by the relative likelihood that OH will react with NO2 or instead with a volatile organic compound (VOC). Over the past decades, changes in anthropogenic emissions of both NOx and VOCs have led to a significant increase in the overall importance of RONO2 chemistry to NOx loss. We find that this shift is associated with a decreased effectiveness of NOx emissions reductions on ozone production in polluted areas and increased transport of NOx from source to receptor regions. This change in chemistry, combined with changes in the spatial pattern of NOx emissions, is observed to be leading to a flatter distribution of NO2 across the United States, potentially transforming ozone air pollution from a local issue into a regional one.
- Published
- 2020
48. Supplementary material to 'A method for using stationary networks to observe long term trends of on-road emissions factors of primary aerosol from heavy duty vehicles'
- Author
-
Helen Lorraine Fitzmaurice and Ronald C. Cohen
- Published
- 2022
49. A method for using stationary networks to observe long term trends of on-road emissions factors of primary aerosol from heavy duty vehicles
- Author
-
Helen Lorraine Fitzmaurice and Ronald C. Cohen
- Subjects
viruses ,virus diseases ,biochemical phenomena, metabolism, and nutrition - Abstract
Heavy-duty vehicles (HDV) contribute a significant, but decreasing, fraction of primary aerosol emissions in urban areas. Previous studies have shown spatial heterogeneity in compliance with regulation. Consequently, location-specific emissions factors are necessary to describe primary particulate matter (PM) emissions by HDV. Using near-road observations from the Bay Area Air Quality Management District (BAAQMD) network over the 2009–2020 period in combination with Caltrans measurements of vehicle number and type, we determine primary PM2.5 emission factors from HDV on highways in the San Francisco Bay Area. We demonstrate that HDV primary aerosol emission factors derived using this method are in line with observations by other studies, that they decreased a by a factor of ~7 in the past decade, and that they are still 2–3 times higher than would be expected if all HDV were in compliance with California HDV regulations.
- Published
- 2022
50. Direct Retrieval of NO 2 Vertical Columns from UV-Vis (390-495 nm) Spectral Radiances Using a Neural Network
- Author
-
Chi Li, Xiaoguang Xu, Xiong Liu, Jun Wang, Kang Sun, Jos van Geffen, Qindan Zhu, Jianzhong Ma, Junli Jin, Kai Qin, Qin He, Pinhua Xie, Bo Ren, and Ronald C. Cohen
- Abstract
Satellite retrievals of columnar nitrogen dioxide (NO 2 ) are essential for the characterization of nitrogen oxides (NO x ) processes and impacts. The requirements of modeled a priori profiles present an outstanding bottleneck in operational satellite NO 2 retrievals. In this work, we instead use neural network (NN) models trained from over 360,000 radiative transfer (RT) simulations to translate satellite radiances across 390-495 nm to total NO 2 vertical column (NO 2 C). Despite the wide variability of the many input parameters in the RT simulations, only a small number of key variables were found essential to the accurate prediction of NO 2 C, including observing angles, surface reflectivity and altitude, and several key principal component scores of the radiances. In addition to the NO 2 C, the NN training and cross-validation experiments show that the wider retrieval window allows some information about the vertical distribution to be retrieved (e.g., extending the rightmost wavelength from 465 to 495 nm decreases the root-mean-square-error by 0.75%) under high-NO 2 C conditions. Applying to four months of TROPOMI data, the trained NN model shows strong ability to reproduce the NO 2 C observed by the ground-based Pandonia Global Network. The coefficient of determination ( R 2 , 0.75) and normalized mean bias (NMB, -33%) are competitive with the level 2 operational TROPOMI product ( R 2 = 0.77 , NMB = − 29 % ) over clear ( geometric cloud fraction < 0.2 ) and polluted ( N O 2 C ≥ 7.5 × 10 15 molecules/cm 2 ) regions. The NN retrieval approach is ~12 times faster than predictions using high spatial resolution (~3 km) a priori profiles from chemical transport modeling, which is especially attractive to the handling of large volume satellite data.
- Published
- 2022
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