scholarly journals The long-term trend and production sensitivity change in the US ozone pollution from observations and model simulations

2020 ◽  
Vol 20 (5) ◽  
pp. 3191-3208 ◽  
Author(s):  
Hao He ◽  
Xin-Zhong Liang ◽  
Chao Sun ◽  
Zhining Tao ◽  
Daniel Q. Tong
Keyword(s):  
United States ◽  
Air Quality ◽  
Surface Ozone ◽  
The United States ◽  
Early Morning ◽  
Ozone Pollution ◽  
Late Afternoon ◽  
The Past ◽  
The Us

Abstract. We investigated the ozone pollution trend and its sensitivity to key precursors from 1990 to 2015 in the United States using long-term EPA Air Quality System (AQS) observations and mesoscale simulations. The modeling system, a coupled regional climate–air quality model (CWRF-CMAQ; Climate-Weather Research Forecast and the Community Multiscale Air Quality), captured well the summer surface ozone pollution during the past decades, having a mean slope of linear regression with AQS observations of ∼0.75. While the AQS network has limited spatial coverage and measures only a few key chemical species, CWRF-CMAQ provides comprehensive simulations to enable a more rigorous study of the change in ozone pollution and chemical sensitivity. Analysis of seasonal variations and diurnal cycle of ozone observations showed that peak ozone concentrations in the summer afternoon decreased ubiquitously across the United States, up to 0.5 ppbv yr−1 in major non-attainment areas such as Los Angeles, while concentrations at certain hours such as the early morning and late afternoon increased slightly. Consistent with the AQS observations, CMAQ simulated a similar decreasing trend of peak ozone concentrations in the afternoon, up to 0.4 ppbv yr−1, and increasing ozone trends in the early morning and late afternoon. A monotonically decreasing trend (up to 0.5 ppbv yr−1) in the odd oxygen (Ox=O3+NO2) concentrations are simulated by CMAQ at all daytime hours. This result suggests that the increased ozone in the early morning and late afternoon was likely caused by reduced NO–O3 titration, driven by continuous anthropogenic NOx emission reductions in the past decades. Furthermore, the CMAQ simulations revealed a shift in chemical regimes of ozone photochemical production. From 1990 to 2015, surface ozone production in some metropolitan areas, such as Baltimore, has transited from a VOC-sensitive environment (>50 % probability) to a NOx-sensitive regime. Our results demonstrated that the long-term CWRF-CMAQ simulations can provide detailed information of the ozone chemistry evolution under a changing climate and may partially explain the US ozone pollution responses to regional and national regulations.

scholarly journals The long-term trend and production sensitivity change of the U.S. ozone pollution from observations and model simulations

2019 ◽  
Author(s):  
Hao He ◽  
Xin-Zhong Liang ◽  
Chao Sun ◽  
Zhining Tao ◽  
Daniel Q. Tong
Keyword(s):  
United States ◽  
Surface Ozone ◽  
The United States ◽  
Early Morning ◽  
Ozone Pollution ◽  
Late Afternoon ◽  
The Past ◽  
Ozone Concentrations ◽  
The U.S

Abstract. We investigated the ozone pollution trend and its sensitivity to key precursors from 1990 to 2015 in the United States using long-term EPA AQS observations and mesoscale simulations. The modeling system, a coupled regional climate–air quality (CWRF-CMAQ) model, well captured summer surface ozone pollution during the past decades, having a mean slope of linear regression with AQS observations at ~ 0.75. While the AQS network has limited spatial coverage and measures only a few key chemical species, the CWRF-CMAQ provides comprehensive simulations to enable a more rigorous study of the change in ozone pollution and chemical sensitivity. Analysis of seasonal variations and diurnal cycle of ozone observations showed that peak ozone concentrations in the summer afternoon decreased ubiquitously across the United States, up to 0.5 ppbv/yr in major non-attainment areas such as Los Angeles, while concentrations at other hours such as the early morning and late afternoon increased slightly. Consistent with the AQS observations, CMAQ simulated a similar decreasing trend of peak ozone concentrations in the afternoon, up to 0.4 ppbv/yr, and increasing ozone trends in the early morning and late afternoon. While a monotonic decreasing trend (up to 0.5 ppbv/yr) in the odd oxygen (Ox = O3 + NO2) concentrations are simulated by CMAQ at all daytime hours. This result suggests that the increased ozone in the early morning and late afternoon was likely caused by reduced NO-O3 titration driven by continuous anthropogenic NOx emission reductions in the past decades. Furthermore, the CMAQ simulations revealed a shift in chemical regimes of ozone photochemical production. From 1990 to 2015, surface ozone production in some metropolitan areas, such as Baltimore, has transited from VOC-sensitive environment (> 50 % probability) to NOx-sensitive regime. Our results demonstrated that the long-term CWRF-CMAQ simulations can provide detailed information of the ozone chemistry evolution under a changing climate, and may partially explain the U.S. ozone pollution responses to regional and national regulations.

scholarly journals Assessment of long-term WRF–CMAQ simulations for understanding direct aerosol effects on radiation "brightening" in the United States

2015 ◽  
Vol 15 (21) ◽  
pp. 12193-12209 ◽  
Author(s):  
C.-M. Gan ◽  
J. Pleim ◽  
R. Mathur ◽  
C. Hogrefe ◽  
C. N. Long ◽  
...  
Keyword(s):  
United States ◽  
Air Quality ◽  
The United States ◽  
Control Measures ◽  
Air Quality Model ◽  
Clear Sky ◽  
The Past ◽  
Western Us ◽  
Tropospheric Aerosol

Abstract. Long-term simulations with the coupled WRF–CMAQ (Weather Research and Forecasting–Community Multi-scale Air Quality) model have been conducted to systematically investigate the changes in anthropogenic emissions of SO2 and NOx over the past 16 years (1995–2010) across the United States (US), their impacts on anthropogenic aerosol loading over North America, and subsequent impacts on regional radiation budgets. In particular, this study attempts to determine the consequences of the changes in tropospheric aerosol burden arising from substantial reductions in emissions of SO2 and NOx associated with control measures under the Clean Air Act (CAA) especially on trends in solar radiation. Extensive analyses conducted by Gan et al. (2014a) utilizing observations (e.g., SURFRAD, CASTNET, IMPROVE, and ARM) over the past 16 years (1995–2010) indicate a shortwave (SW) radiation (both all-sky and clear-sky) "brightening" in the US. The relationship of the radiation brightening trend with decreases in the aerosol burden is less apparent in the western US. One of the main reasons for this is that the emission controls under the CAA were aimed primarily at reducing pollutants in areas violating national air quality standards, most of which were located in the eastern US, while the relatively less populated areas in the western US were less polluted at the beginning of this study period. Comparisons of model results with observations of aerosol optical depth (AOD), aerosol concentration, and radiation demonstrate that the coupled WRF–CMAQ model is capable of replicating the trends well even though it tends to underestimate the AOD. In particular, the sulfate concentration predictions were well matched with the observations. The discrepancies found in the clear-sky diffuse SW radiation are likely due to several factors such as the potential increase of ice particles associated with increasing air traffic, the definition of "clear-sky" in the radiation retrieval methodology, and aerosol semi-direct and/or indirect effects which cannot be readily isolated from the observed data.

scholarly journals Observations and modeling of air quality trends over 1990–2010 across the Northern Hemisphere: China, the United States and Europe

2014 ◽  
Vol 14 (18) ◽  
pp. 25453-25501 ◽  
Author(s):  
J. Xing ◽  
R. Mathur ◽  
J. Pleim ◽  
C. Hogrefe ◽  
C.-M. Gan ◽  
...  
Keyword(s):  
United States ◽  
Air Quality ◽  
Northern Hemisphere ◽  
Linear Response ◽  
Eastern China ◽  
The United States ◽  
Nox Emissions ◽  
Voc Emissions ◽  
The Past ◽  
The Us

Abstract. Trends in air quality across the Northern Hemisphere over a 21 year period (1990–2010) were simulated using the CMAQ multiscale chemical transport model driven by meteorology from WRF simulations and internally consistent historical emission inventories obtained from EDGAR. Thorough comparison with several ground observation networks mostly over Europe and North America was conducted to evaluate the model performance as well as the ability of CMAQ to reproduce the observed trends in air quality over the past two decades in three regions: eastern China, the continental United States and Europe. The model successfully reproduced the observed decreasing trends in SO2, NO2, maxima 8 h O3, SO42− and EC in the US and Europe. However, the model fails to reproduce the decreasing trends in NO3− in the US, potentially pointing to uncertainties of NH3 emissions. The model failed to capture the 6 year trends of SO2 and NO2 in CN-API from 2005–2010, but reproduced the observed pattern of O3 trends shown in three WDCGG sites over eastern Asia. Due to the coarse spatial resolution employed in these calculations, predicted SO2 and NO2 concentrations are underestimated relative to all urban networks, i.e., US-AQS (NMB = −46 and −54%), EU-AIRBASE (NMB = −12 and −57%) and CN-API (NMB = −36 and −68%). Conversely, at the rural network EU-EMEP SO2 is overestimated (NMB from 4 to 150%) while NO2 is simulated well (NMB within ±15%) in all seasons. Correlations between simulated and observed winter time daily maxima 8 h (DM8) O3 are poor compared to other seasons for all networks. Better correlation between simulated and observed SO42− was found compared to that for SO2. Underestimation of summer SO42− in the US may be associated with the uncertainty in precipitation and associated wet scavenging representation in the model. The model exhibits worse performance for NO3− predictions, particularly in summer, due to high uncertainties in the gas/particle partitioning of NO3− as well as seasonal variations of NH3 emissions. There are high correlations (R > 0.5) between observed and simulated EC, although the model underestimates the EC concentration by 65% due to the coarse grid resolution as well as uncertainties in the PM speciation profile associated with EC emissions. The almost linear response seen in the trajectory of modeled O3 changes in the eastern China over the past two decades, suggests that control strategies that focus on combined control of NOx and VOC emissions with a ratio of 0.46 may provide the most effective means for O3 reductions for the region devoid of non-linear response potentially associated with NOx or VOC limitation resulting from alternate strategies. The response of O3 is more sensitive to changes in NOx emissions in the eastern US because the relative abundance of biogenic VOC emissions tends to reduce the effectiveness of VOC controls. Increasing NH3 levels offset the relative effectiveness of NOx controls in reducing the relative fraction of aerosol NO3− formed from declining NOx emissions in the eastern US, while the control effectiveness was assured by the simultaneous control of NH3 emission in Europe.

scholarly journals Observations and modeling of air quality trends over 1990–2010 across the Northern Hemisphere: China, the United States and Europe

2015 ◽  
Vol 15 (5) ◽  
pp. 2723-2747 ◽  
Author(s):  
J. Xing ◽  
R. Mathur ◽  
J. Pleim ◽  
C. Hogrefe ◽  
C.-M. Gan ◽  
...  
Keyword(s):  
United States ◽  
Air Quality ◽  
Northern Hemisphere ◽  
Eastern China ◽  
The United States ◽  
Quality Data ◽  
Nox Emissions ◽  
Voc Emissions ◽  
The Past ◽  
The Us

Abstract. Trends in air quality across the Northern Hemisphere over a 21-year period (1990–2010) were simulated using the Community Multiscale Air Quality (CMAQ) multiscale chemical transport model driven by meteorology from Weather Research and Forecasting (WRF) simulations and internally consistent historical emission inventories obtained from EDGAR. Thorough comparison with several ground observation networks mostly over Europe and North America was conducted to evaluate the model performance as well as the ability of CMAQ to reproduce the observed trends in air quality over the past 2 decades in three regions: eastern China, the continental United States and Europe. The model successfully reproduced the observed decreasing trends in SO2, NO2, 8 h O3 maxima, SO42− and elemental carbon (EC) in the US and Europe. However, the model fails to reproduce the decreasing trends in NO3− in the US, potentially pointing to uncertainties of NH3 emissions. The model failed to capture the 6-year trends of SO2 and NO2 in CN-API (China – Air Pollution Index) from 2005 to 2010, but reproduced the observed pattern of O3 trends shown in three World Data Centre for Greenhouse Gases (WDCGG) sites over eastern Asia. Due to the coarse spatial resolution employed in these calculations, predicted SO2 and NO2 concentrations are underestimated relative to all urban networks, i.e., US-AQS (US – Air Quality System; normalized mean bias (NMB) = −38% and −48%), EU-AIRBASE (European Air quality data Base; NMB = −18 and −54%) and CN-API (NMB = −36 and −68%). Conversely, at the rural network EU-EMEP (European Monitoring and Evaluation Programme), SO2 is overestimated (NMB from 4 to 150%) while NO2 is simulated well (NMB within ±15%) in all seasons. Correlations between simulated and observed O3 wintertime daily 8 h maxima (DM8) are poor compared to other seasons for all networks. Better correlation between simulated and observed SO42− was found compared to that for SO2. Underestimation of summer SO42− in the US may be associated with the uncertainty in precipitation and associated wet scavenging representation in the model. The model exhibits worse performance for NO3− predictions, particularly in summer, due to high uncertainties in the gas/particle partitioning of NO3− as well as seasonal variations of NH3 emissions. There are high correlations (R > 0.5) between observed and simulated EC, although the model underestimates the EC concentration by 65% due to the coarse grid resolution as well as uncertainties in the PM speciation profile associated with EC emissions. The almost linear response seen in the trajectory of modeled O3 changes in eastern China over the past 2 decades suggests that control strategies that focus on combined control of NOx and volatile organic compound (VOC) emissions with a ratio of 0.46 may provide the most effective means for O3 reductions for the region devoid of nonlinear response potentially associated with NOx or VOC limitation resulting from alternate strategies. The response of O3 is more sensitive to changes in NOx emissions in the eastern US because the relative abundance of biogenic VOC emissions tends to reduce the effectiveness of VOC controls. Increasing NH3 levels offset the relative effectiveness of NOx controls in reducing the relative fraction of aerosol NO3− formed from declining NOx emissions in the eastern US, while the control effectiveness was assured by the simultaneous control of NH3 emission in Europe.

scholarly journals America's Debate over the Rise of China

2016 ◽  
Vol 226 ◽  
pp. 538-550 ◽  
Author(s):  
John W. Garver
Keyword(s):  
United States ◽  
The United States ◽  
The Past ◽  
Friendly Relation ◽  
The Us ◽  
Four Books ◽  
Rise Of China ◽  
Chinese Military ◽  
The Rise Of China

The rapid growth of China's power combined with the intensification of rivalry between the United States and China over the past several years has triggered a re-thinking of US policy toward the rise of China. America's traditional policy of supporting China's rise as a rich, strong and peaceful country in hopes of building a cooperative and generally friendly relation with China over the long term, is being called into question. Critics charge that that traditional policy is backfiring, playing into Beijing's wiles and producing a China so powerful it could well become the greatest challenge to the United States in its history. Other analysts offer a less jaundiced view of China, but all manifest apprehension over whether China will use its growing power to challenge the US. Earlier iterations of a similar debate have come and gone, but the closing distance between US and Chinese military, economic and technological power has brought this debate much closer to the US mainstream. Indeed, one or two of these books may represent the mainstream of US thinking. Together, the four books lay out the topography of the US debate.

The Riddle of a Common History

2009 ◽  
Vol 1 (1) ◽  
pp. 93-116 ◽  
Author(s):  
Mauricio Tenorio-Trillo
Keyword(s):  
United States ◽  
Common Ground ◽  
The United States ◽  
History Textbooks ◽  
Recent History ◽  
History Textbook ◽  
The Past ◽  
The Us ◽  
Constant Part ◽  
Intrinsic Component

By identifying two general issues in recent history textbook controversies worldwide (oblivion and inclusion), this article examines understandings of the United States in Mexico's history textbooks (especially those of 1992) as a means to test the limits of historical imagining between U. S. and Mexican historiographies. Drawing lessons from recent European and Indian historiographical debates, the article argues that many of the historical clashes between the nationalist historiographies of Mexico and the United States could be taught as series of unsolved enigmas, ironies, and contradictions in the midst of a central enigma: the persistence of two nationalist historiographies incapable of contemplating their common ground. The article maintains that lo mexicano has been a constant part of the past and present of the US, and lo gringo an intrinsic component of Mexico's history. The di erences in their historical tracks have been made into monumental ontological oppositions, which are in fact two tracks—often overlapping—of the same and shared con ictual and complex experience.

From Start-Up to Scale-Up

2018 ◽  
Author(s):  
Gilles Duruflé ◽  
Thomas Hellmann ◽  
Karen Wilson
Keyword(s):  
United States ◽  
Conceptual Framework ◽  
Public Policies ◽  
Scale Up ◽  
The United States ◽  
Smart Money ◽  
Start Up ◽  
The Us ◽  
The Creation

This chapter examines the challenge for entrepreneurial companies of going beyond the start-up phase and growing into large successful companies. We examine the long-term financing of these so-called scale-up companies, focusing on the United States, Europe, and Canada. The chapter first provides a conceptual framework for understanding the challenges of financing scale-ups. It emphasizes the need for investors with deep pockets, for smart money, for investor networks, and for patient money. It then shows some data about the various aspects of financing scale-ups in the United States, Europe, and Canada, showing how Europe and Canada are lagging behind the US relatively more at the scale-up than the start-up stage. Finally, the chapter raises the question of long-term public policies for supporting the creation of a better scale-up environment.

scholarly journals Fungicide Sensitivity of U.S. Genotypes of Phytophthora infestans to Six Oomycete-Targeted Compounds

Plant Disease ◽  
2015 ◽  
Vol 99 (5) ◽  
pp. 659-666 ◽  
Author(s):  
Amanda Saville ◽  
Kim Graham ◽  
Niklaus J. Grünwald ◽  
Kevin Myers ◽  
William E. Fry ◽  
...  
Keyword(s):  
United States ◽  
Phytophthora Infestans ◽  
The United States ◽  
Effective Concentration ◽  
Response Curves ◽  
Baseline Sensitivity ◽  
Fungicide Sensitivity ◽  
The Past ◽  
The Us

Phytophthora infestans causes potato late blight, an important and costly disease of potato and tomato crops. Seven clonal lineages of P. infestans identified recently in the United States were tested for baseline sensitivity to six oomycete-targeted fungicides. A subset of the dominant lineages (n = 45) collected between 2004 and 2012 was tested in vitro on media amended with a range of concentrations of either azoxystrobin, cyazofamid, cymoxanil, fluopicolide, mandipropamid, or mefenoxam. Dose-response curves and values for the effective concentration at which 50% of growth was suppressed were calculated for each isolate. The US-8 and US-11 clonal lineages were insensitive to mefenoxam while the US-20, US-21, US-22, US-23, and US-24 clonal lineages were sensitive to mefenoxam. Insensitivity to azoxystrobin, cyazofamid, cymoxanil, fluopicolide, or mandipropamid was not detected within any lineage. Thus, current U.S. populations of P. infestans remained sensitive to mefenoxam during the displacement of the US-22 lineage by US-23 over the past 5 years.

DIPHTHERIA IN THE UNITED STATES, 1959-1960

PEDIATRICS ◽  
1962 ◽  
Vol 30 (2) ◽  
pp. 194-205
Author(s):  
Theodore C. Doege ◽  
Clark W. Heath ◽  
Ida L. Sherman
Keyword(s):  
United States ◽  
Communicable Disease ◽  
Case Fatality ◽  
The United States ◽  
Surveillance Data ◽  
Term Trend ◽  
The Past ◽  
Primary Series ◽  
Long Term Trend

Diphtheria attack rates and cases, and to a much lesser extent case-fatality rates, have fallen steadily within the United States during the past 25 years. However, during 1959 and 1960 there was a halt in this long-term trend. Epidemiologic data on 868 clinical cases of diphtheria occurring in 1959 and 873 cases in 1960 were submitted to the Communicable Disease Center by 45 states. The cases and several major outbreaks tended to concentrate in the southern and southwestern states. Attack rates and deaths were highest for children under 10 years, and attack rates were more than five times greater for nonwhite children. Analysis of 1960 immunization data shows that 72% of the patients had received no immunizations. Fifty-five per cent of carriers, but only 18% of persons with bacteriologically confirmed cases, had received a primary series. Only 1 person of 58 fatal cases occurring in 1960 had received a primary series. Certain problems for future investigation, disclosed by the surveillance data, are discussed.

Effects of ozone and climate on historical (1980-2015) crop yields in the United States: Implication for mid-21st century projection

2021 ◽  
Author(s):  
Yabin Da ◽  
Yangyang Xu ◽  
Bruce McCarl
Keyword(s):  
Climate Change ◽  
United States ◽  
Winter Wheat ◽  
Crop Yields ◽  
Time Window ◽  
Surface Ozone ◽  
The United States ◽  
Ozone Exposure ◽  
Future Climate Change ◽  
Ozone Pollution

<p>Surface ozone pollution has been proven to impose significant damages on crops. However, the quantification of the damages was extensively derived from chamber experiments, which is not representative of actual results in farm fields due to the limitations of spatial scale, time window, etc. In this work, we attempt to empirically fill this gap using county-level data in the United States from 1980 to 2015. We explore ozone impacts on corn, soybeans, spring wheat, winter wheat, barley, cotton, peanuts, rice, sorghum, and sunflower. We also incorporate a variety of climate variables to investigate potential ozone-climate interactions. More importantly, we shed light on future yield consequences of ozone and climate change individually and jointly under a moderate warming scenario. Our findings suggest significant negative impacts of ozone exposure for eight of the ten crops we examined, excepting barley and winter wheat, which contradicts experimental results. The average annual damages were estimated at $6.03 billion (in 2015 U.S. dollar) from 1980 to 2015. We also find rising temperatures tend to worsen ozone damages while water supply would mitigate that. Finally, elevated ozone driven by future climate change would cause much smaller damages than the direct effects of climate change itself.</p>

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