scholarly journals Winter observations of ClNO<sub>2</sub> in northern China: Spatiotemporal variability and insights into daytime peaks

2021 ◽  
Author(s):  
Men Xia ◽  
Xiang Peng ◽  
Weihao Wang ◽  
Chuan Yu ◽  
Zhe Wang ◽  
...  
Keyword(s):  
Northern China ◽  
Spatiotemporal Variability ◽  
Model Calculations ◽  
Dinitrogen Pentoxide ◽  
Mixing Ratios ◽  
The North ◽  
Urban Rural ◽  
Rural Sites ◽  
Related Compounds ◽  
Cl Atoms

Abstract. Nitryl chloride (ClNO2) is an important chlorine reservoir in the atmosphere that affects the oxidation of volatile organic compounds (VOCs) and the production of ROx radicals and ozone (O3). This study presents measurements of ClNO2 and related compounds at urban, rural, and mountain sites in the winter of 2017–2018 over the North China Plain (NCP). The nocturnal concentrations of ClNO2 were lower at the urban and rural sites but higher at the mountain site. The winter concentrations of ClNO2 were generally lower than the summer concentrations that were previously observed at these sites, which was due to the lower nitrate radical (NO3) production rate (P(NO3) and the smaller N2O5 uptake coefficients (γ(N2O5)) in winter, despite the higher dinitrogen pentoxide (N2O5) to NO3 ratios in winter. Significant daytime peaks of ClNO2 were observed at all the sites during the winter campaigns, with ClNO2 mixing ratios of up to 1.3 ppbv. Vertical transport of ClNO2 from the residual layers and prolonged photochemical lifetime of ClNO2 in winter may explain the elevated daytime concentrations. The daytime-averaged chlorine radical (Cl) production rates (P(Cl)) from the daytime ClNO2 were 0.17, 0.11, and 0.12 ppbv h−1 at the rural, urban, and mountain sites, respectively, which were approximately 3–4 times higher than the campaign-averaged conditions. Box model calculations showed that the Cl atoms liberated during the daytime peaks of ClNO2 increased the ROx levels by up to 27–37 % and increased the daily O3 productions by up to 13–18 %.

scholarly journals Rapid intercontinental air pollution transport associated with a meteorological bomb

2003 ◽  
Vol 3 (4) ◽  
pp. 969-985 ◽  
Author(s):  
A. Stohl ◽  
H. Huntrieser ◽  
A. Richter ◽  
S. Beirle ◽  
O. R. Cooper ◽  
...  
Keyword(s):  
Transport Model ◽  
Pollution Transport ◽  
Tracer Transport ◽  
High Wind ◽  
Model Calculations ◽  
Wind Speeds ◽  
Mixing Ratios ◽  
The North ◽  
Intercontinental Transport ◽  
Remote Troposphere

Abstract. Intercontinental transport (ICT) of trace substances normally occurs on timescales ranging from a few days to several weeks. In this paper an extraordinary episode in November 2001 is presented, where pollution transport across the North Atlantic took only about one day. The transport mechanism, termed here an intercontinental pollution express highway because of the high wind speeds, was exceptional, as it involved an explosively generated cyclone, a so-called meteorological "bomb''. To the authors' knowledge, this is the first study describing pollution transport in a bomb. The discovery of this event was based on tracer transport model calculations and satellite measurements of NO2, a species with a relatively short lifetime in the atmosphere, which could be transported that far only because of the high wind speeds produced by the bomb. A 15-year transport climatology shows that intercontinental express highways are about four times more frequent in winter than in summer, in agreement with bomb climatologies. The climatology furthermore suggests that intercontinental express highways may be important for the budget of short-lived substances in the remote troposphere. For instance, for a substance with a lifetime of 1 day, express highways may be responsible for about two thirds of the total ICT. We roughly estimate that express highways connecting North America with Europe enhance the average NOx mixing ratios over Europe, due to North American emissions, by about 2-3 pptv in winter.

scholarly journals Radical chemistry at a rural site (Wangdu) in the North China Plain: Observation and model calculations of OH, HO<sub>2</sub> and RO<sub>2</sub> radicals

2016 ◽  
Author(s):  
Zhaofeng Tan ◽  
Hendrik Fuchs ◽  
Keding Lu ◽  
Birger Bohn ◽  
Sebastian Broch ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Chemical Mechanism ◽  
Ozone Production ◽  
Rural Site ◽  
Daily Maximum ◽  
Model Calculations ◽  
Mixing Ratios ◽  
The North ◽  
The North China Plain

Abstract. A comprehensive field campaign was carried out in summer 2014 in Wangdu located in the North China Plain. A month of continuous OH, HO2 and RO2 measurements were achieved. Observations of radicals by laser induced fluorescence (LIF) technique gave daily maximum concentrations between (5–15) × 106 cm−3, (3–14) × 108 cm−3 and (3–15) × 108 cm−3 for OH, HO2 and RO2, respectively. Measured OH reactivities (inverse OH lifetimes) were 10 to 20 s−1 during daytime. A chemical box model constrained by trace-gas observations and based on a state-of-the-art chemical mechanism is used to interpret the observed radical concentrations. In general, the model can reasonably well reproduce measured radical concentrations during daytime. Like in previous field campaigns in China, modelled and measured OH concentrations agree for NO mixing ratios higher than 1 ppbv, but systematic discrepancies are observed in the afternoon for NO mixing ratios of less than 300 pptv (the model-measurement ratio is between 1.4 to 2 in this case). If additional OH recycling equivalent to 100 pptv NO is assumed, the model is also capable of reproducing the observed OH concentrations for conditions of high VOC and low NOx concentrations with good agreement in HO2 and RO2. Observed RO2 concentrations are underestimated in the morning hours by a factor of 3 to 5. This indicates that an additional chemical source of RO2 is missing in the model. The OH reactivity is also underpredicted in the early morning. Increasing VOC concentrations to match measured OH reactivity helps to reduce the discrepancy between modelled and measured RO2. The underprediction of RO2 coincides with high NO concentrations and therefore leads to a significant underestimation of the local ozone production rates determined from the peroxy radical (HO2 and RO2) reactions with NO. The underestimation corresponds to a daily integral ozone production of about 20 ppbv per day.

scholarly journals Rapid intercontinental air pollution transport associated with a meteorological bomb

2003 ◽  
Vol 3 (2) ◽  
pp. 2101-2141 ◽  
Author(s):  
A. Stohl ◽  
H. Huntrieser ◽  
A. Richter ◽  
S. Beirle ◽  
O. Cooper ◽  
...  
Keyword(s):  
Transport Model ◽  
Pollution Transport ◽  
Satellite Measurements ◽  
Model Calculations ◽  
Wind Speeds ◽  
Mixing Ratios ◽  
The North ◽  
Intercontinental Transport ◽  
Remote Troposphere ◽  
Rough Calculation

Abstract. Intercontinental transport (ICT) of trace substances normally occurs on timescales ranging from a few days to several weeks. In this paper an extraordinary episode in November 2001 is presented, where pollution transport across the North Atlantic took only about one day. The transport mechanism, termed here an intercontinental pollution express highway, was exceptional, as it involved an explosively generated cyclone, a so-called meteorological "bomb". To the authors' knowledge, this is the first study describing pollution transport in a bomb. The discovery of this event was based on transport model calculations and satellite measurements of NO2, a species with a relatively short lifetime in the atmosphere, which could be transported that far only because of the high wind speeds produced by the bomb. A 15-year transport climatology shows that intercontinental express highways are about four times more frequent in winter than in summer, in agreement with bomb climatologies. The climatology furthermore reveals that intercontinental express highways may be important for the budget of short-lived substances in the remote troposphere. For instance, for a substance with a lifetime of 1 day, express highways may be responsible for about two thirds of the total ICT. A rough calculation suggests that express highways connecting North America with Europe enhance the average NOx mixing ratios over Europe, due to North American emissions, by about 2–3 pptv in winter.

scholarly journals Significant concentrations of nitryl chloride sustained in the morning: Investigations of the causes and impacts on ozone production in a polluted region of northern China

2016 ◽  
Author(s):  
Yee Jun Tham ◽  
Zhe Wang ◽  
Qinyi Li ◽  
Hui Yun ◽  
Weihao Wang ◽  
...  
Keyword(s):  
Inversion Layer ◽  
Northern China ◽  
Residual Layer ◽  
Ozone Production ◽  
Rural Site ◽  
Ionization Mass ◽  
Dinitrogen Pentoxide ◽  
Mixing Ratios ◽  
Nitryl Chloride ◽  
Nocturnal Inversion

Abstract. Nitryl chloride (ClNO2) is a dominant source of chlorine radical in polluted environment and can significantly affect the atmospheric oxidative chemistry. However, the abundance of ClNO2 and its exact role are not fully understood under different environmental conditions. During the summer of 2014, we deployed a chemical ionization mass spectrometer to measure ClNO2 and dinitrogen pentoxide (N2O5) at a rural site in the polluted North China Plain. Elevated mixing ratios of ClNO2 (> 350 pptv) were observed at most of the nights with low levels of N2O5 (< 200 pptv). The highest ClNO2 mixing ratio of 2070 pptv (1-min average) was observed in a plume from megacity (Tianjin) and was characterized with faster N2O5 heterogeneous loss rate and ClNO2 production rate compared to average condition. The abundant ClNO2 concentration kept increasing even after sunrise and reached a peak 4 hours later. Such highly sustained ClNO2 peaks after sunrise are discrepant from the previously observed typical diurnal pattern. Meteorological and chemical analysis show that the sustained ClNO2 morning peaks are caused by significant ClNO2 production in the residual layer at night followed by downward mixing after break-up of the nocturnal inversion layer in the morning. We estimated that ~ 1.7–4.0 ppbv of ClNO2 would exist in the residual layer in order to maintain the observed morning ClNO2 peaks at the surface site. Observation-based box model analysis show that photolysis of ClNO2 produced chlorine radical with a rate up to 1.12 ppbv h−1, accounting for 10–30 % of primary ROx production in the morning hours. The perturbation in total radical production leads to an increase of integrated daytime net ozone production by 3 % (4.3 ppbv) on average, and with a larger increase of 13 % (11 ppbv) in megacity outflow that was characterized with higher ClNO2 and relatively lower OVOC to NMHC ratio.

scholarly journals Radical chemistry at a rural site (Wangdu) in the North China Plain: observation and model calculations of OH, HO<sub>2</sub> and RO<sub>2</sub> radicals

2017 ◽  
Vol 17 (1) ◽  
pp. 663-690 ◽  
Author(s):  
Zhaofeng Tan ◽  
Hendrik Fuchs ◽  
Keding Lu ◽  
Andreas Hofzumahaus ◽  
Birger Bohn ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Ozone Production ◽  
Rural Site ◽  
Model Calculations ◽  
Radical Chemistry ◽  
Mixing Ratios ◽  
The North ◽  
The North China Plain ◽  
Field Campaigns

Abstract. A comprehensive field campaign was carried out in summer 2014 in Wangdu, located in the North China Plain. A month of continuous OH, HO2 and RO2 measurements was achieved. Observations of radicals by the laser-induced fluorescence (LIF) technique revealed daily maximum concentrations between (5–15)  × 106 cm−3, (3–14)  × 108 cm−3 and (3–15)  × 108 cm−3 for OH, HO2 and RO2, respectively. Measured OH reactivities (inverse OH lifetime) were 10 to 20 s−1 during daytime. The chemical box model RACM 2, including the Leuven isoprene mechanism (LIM), was used to interpret the observed radical concentrations. As in previous field campaigns in China, modeled and measured OH concentrations agree for NO mixing ratios higher than 1 ppbv, but systematic discrepancies are observed in the afternoon for NO mixing ratios of less than 300 pptv (the model–measurement ratio is between 1.4 and 2 in this case). If additional OH recycling equivalent to 100 pptv NO is assumed, the model is capable of reproducing the observed OH, HO2 and RO2 concentrations for conditions of high volatile organic compound (VOC) and low NOx concentrations. For HO2, good agreement is found between modeled and observed concentrations during day and night. In the case of RO2, the agreement between model calculations and measurements is good in the late afternoon when NO concentrations are below 0.3 ppbv. A significant model underprediction of RO2 by a factor of 3 to 5 is found in the morning at NO concentrations higher than 1 ppbv, which can be explained by a missing RO2 source of 2 ppbv h−1. As a consequence, the model underpredicts the photochemical net ozone production by 20 ppbv per day, which is a significant portion of the daily integrated ozone production (110 ppbv) derived from the measured HO2 and RO2. The additional RO2 production from the photolysis of ClNO2 and missing reactivity can explain about 10 % and 20 % of the discrepancy, respectively. The underprediction of the photochemical ozone production at high NOx found in this study is consistent with the results from other field campaigns in urban environments, which underlines the need for better understanding of the peroxy radical chemistry for high NOx conditions.

scholarly journals Two-years of NO<sub>3</sub> radical observations in the boundary layer over the Eastern Mediterranean

2007 ◽  
Vol 7 (2) ◽  
pp. 315-327 ◽  
Author(s):  
M. Vrekoussis ◽  
N. Mihalopoulos ◽  
E. Gerasopoulos ◽  
M. Kanakidou ◽  
P. J. Crutzen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Heterogeneous Reaction ◽  
Eastern Mediterranean ◽  
North Coast ◽  
Data Set ◽  
East Europe ◽  
Dinitrogen Pentoxide ◽  
Mixing Ratios ◽  
The North

Abstract. This is the first study that investigates the seasonal variability of nitrate (NO3) radicals in the marine boundary layer over the East Mediterranean Sea. An extensive data set of NO3 radical observations on the north coast of Crete for more than two years (June 2001–September 2003) is presented here. NO3 radicals follow a distinct seasonal dependency with the highest seasonally average mixing ratios in summer (5.6±1.2 pptv) and the lowest in winter (1.2±1.2 pptv). Episodes with high NO3 mixing ratios have been encountered mainly in polluted air masses originating from mainland Greece, Central and East Europe, and Turkey. Ancillary measurements of ozone, nitrogen dioxide (NO2) and meteorological parameters have been conducted and used to reveal possible relationship with the observed NO3 variability. The acquired NO2 nighttime observations provide the up-to-date most complete overview of NO2 temporal variability in the area. The data show correlations of the NO3 nighttime mixing ratios with temperature (positive), relative humidity (negative) and to a lesser extend with O3 (positive). As inferred from these observations, on average the major sink of NO3 radicals in the area is the heterogeneous reaction of dinitrogen pentoxide (N2O5) on aqueous particles whereas the homogeneous gas phase reactions of NO3 are most important during spring and summer. These observations support a significant contribution of NO3 nighttime chemistry to the oxidizing capacity of the troposphere.

scholarly journals Influence of bulk microphysics schemes upon Weather Research and Forecasting (WRF) version 3.6.1 nor'easter simulations

2017 ◽  
Vol 10 (2) ◽  
pp. 1033-1049 ◽  
Author(s):  
Stephen D. Nicholls ◽  
Steven G. Decker ◽  
Wei-Kuo Tao ◽  
Stephen E. Lang ◽  
Jainn J. Shi ◽  
...  
Keyword(s):  
Radar Reflectivity ◽  
Spatiotemporal Variability ◽  
Weather Research And Forecasting ◽  
Mixing Ratios ◽  
The North ◽  
Simulated Precipitation ◽  
Double Moment ◽  
Reflectivity Data ◽  
The Impact ◽  
Weather Research

Abstract. This study evaluated the impact of five single- or double-moment bulk microphysics schemes (BMPSs) on Weather Research and Forecasting model (WRF) simulations of seven intense wintertime cyclones impacting the mid-Atlantic United States; 5-day long WRF simulations were initialized roughly 24 h prior to the onset of coastal cyclogenesis off the North Carolina coastline. In all, 35 model simulations (five BMPSs and seven cases) were run and their associated microphysics-related storm properties (hydrometer mixing ratios, precipitation, and radar reflectivity) were evaluated against model analysis and available gridded radar and ground-based precipitation products. Inter-BMPS comparisons of column-integrated mixing ratios and mixing ratio profiles reveal little variability in non-frozen hydrometeor species due to their shared programming heritage, yet their assumptions concerning snow and graupel intercepts, ice supersaturation, snow and graupel density maps, and terminal velocities led to considerable variability in both simulated frozen hydrometeor species and radar reflectivity. WRF-simulated precipitation fields exhibit minor spatiotemporal variability amongst BMPSs, yet their spatial extent is largely conserved. Compared to ground-based precipitation data, WRF simulations demonstrate low-to-moderate (0.217–0.414) threat scores and a rainfall distribution shifted toward higher values. Finally, an analysis of WRF and gridded radar reflectivity data via contoured frequency with altitude diagrams (CFADs) reveals notable variability amongst BMPSs, where better performing schemes favored lower graupel mixing ratios and better underlying aggregation assumptions.

scholarly journals Significant concentrations of nitryl chloride sustained in the morning: investigations of the causes and impacts on ozone production in a polluted region of northern China

2016 ◽  
Vol 16 (23) ◽  
pp. 14959-14977 ◽  
Author(s):  
Yee Jun Tham ◽  
Zhe Wang ◽  
Qinyi Li ◽  
Hui Yun ◽  
Weihao Wang ◽  
...  
Keyword(s):  
Inversion Layer ◽  
Northern China ◽  
Residual Layer ◽  
Ozone Production ◽  
Rural Site ◽  
Ionization Mass ◽  
Dinitrogen Pentoxide ◽  
Mixing Ratios ◽  
Nitryl Chloride ◽  
Nocturnal Inversion

Abstract. Nitryl chloride (ClNO2) is a dominant source of chlorine radical in polluted environment, and can significantly affect the atmospheric oxidative chemistry. However, the abundance of ClNO2 and its exact role are not fully understood under different environmental conditions. During the summer of 2014, we deployed a chemical ionization mass spectrometer to measure ClNO2 and dinitrogen pentoxide (N2O5) at a rural site in the polluted North China Plain. Elevated mixing ratios of ClNO2 (> 350 pptv) were observed at most of the nights with low levels of N2O5 (< 200 pptv). The highest ClNO2 mixing ratio of 2070 pptv (1 min average) was observed in a plume from a megacity (Tianjin), and was characterized with a faster N2O5 heterogeneous loss rate and ClNO2 production rate compared to average conditions. The abundant ClNO2 concentration kept increasing even after sunrise, and reached a peak 4 h later. Such highly sustained ClNO2 peaks after sunrise are discrepant from the previously observed typical diurnal pattern. Meteorological and chemical analysis shows that the sustained ClNO2 morning peaks are caused by significant ClNO2 production in the residual layer at night followed by downward mixing after breakup of the nocturnal inversion layer in the morning. We estimated that  ∼  1.7–4.0 ppbv of ClNO2 would exist in the residual layer in order to maintain the observed morning ClNO2 peaks at the surface site. Observation-based box model analysis show that photolysis of ClNO2 produced chlorine radical with a rate up to 1.12 ppbv h−1, accounting for 10–30 % of primary ROx production in the morning hours. The perturbation in total radical production leads to an increase of integrated daytime net ozone production by 3 % (4.3 ppbv) on average, and with a larger increase of 13 % (11 ppbv) in megacity outflow that was characterized with higher ClNO2 and a relatively lower oxygenated hydrocarbon (OVOC) to non-methane hydrocarbon (NMHC) ratio.

Poverty-Reducing Growth Strategy in Poor Countries

2005 ◽  
pp. 103-134
Author(s):  
Rodney Schmidt
Keyword(s):  
Low Income ◽  
Poverty Reduction ◽  
Growth Strategy ◽  
Poverty Traps ◽  
Income Poverty ◽  
Poor Countries ◽  
Land Redistribution ◽  
Policy Choices ◽  
The North ◽  
Urban Rural

This paper synthesizes and develops research undertaken by participants in The North-South Institute project, "Macroeconomic policy choices for growth and poverty reduction" in low- income developing countries.1 The project analysed the features of poverty and growth in seven poor countries of varying circumstances and proposed macroeconomic and growth policies for poverty reduction for them. The research was guided by the question: "How does poverty inform growth strategy?" Our research provides evidence of the channels through which growth and distribution or poverty processes depend on each other and respond to policy together. We encapsulate the messages of these case studies in the following six propositions, discussed at length in the paper: i) macroeconomic stability reduces poverty; ii) land redistribution enhances growth; iii) income poverty traps constrain growth; iv) urban-rural growth disparities drive income inequality; v) regional poverty traps resist growth, and vi) ley growth policies can aggravate poverty gaps.  The propositions suggest growth policies that may be either of two types in terms of impact on growth and distribution. They have the potential to enhance both growth and distribution (win-win) or to enhance growth while aggravating income gaps or vice versa (win-lose).

scholarly journals Assessment of Tropospheric Concentrations of NO2 from the TROPOMI/Sentinel-5 Precursor for the Estimation of Long-Term Exposure to Surface NO2 over South Korea

2021 ◽  
Vol 13 (10) ◽  
pp. 1877
Author(s):  
Ukkyo Jeong ◽  
Hyunkee Hong
Keyword(s):  
South Korea ◽  
Spatial Resolution ◽  
Atmospheric Composition ◽  
Mixing Ratio ◽  
Mean Values ◽  
Mixing Ratios ◽  
Tropospheric No2 ◽  
Korean Ministry ◽  
Surface Mixing ◽  
Rural Sites

Since April 2018, the TROPOspheric Monitoring Instrument (TROPOMI) has provided data on tropospheric NO2 column concentrations (CTROPOMI) with unprecedented spatial resolution. This study aims to assess the capability of TROPOMI to acquire high spatial resolution data regarding surface NO2 mixing ratios. In general, the instrument effectively detected major and moderate sources of NO2 over South Korea with a clear weekday–weekend distinction. We compared the CTROPOMI with surface NO2 mixing ratio measurements from an extensive ground-based network over South Korea operated by the Korean Ministry of Environment (SKME; more than 570 sites), for 2019. Spatiotemporally collocated CTROPOMI and SKME showed a moderate correlation (correlation coefficient, r = 0.67), whereas their annual mean values at each site showed a higher correlation (r = 0.84). The CTROPOMI and SKME were well correlated around the Seoul metropolitan area, where significant amounts of NO2 prevailed throughout the year, whereas they showed lower correlation at rural sites. We converted the tropospheric NO2 from TROPOMI to the surface mixing ratio (STROPOMI) using the EAC4 (ECMWF Atmospheric Composition Reanalysis 4) profile shape, for quantitative comparison with the SKME. The estimated STROPOMI generally underestimated the in-situ value obtained, SKME (slope = 0.64), as reported in previous studies.

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