scholarly journals Megacity impacts on regional ozone formation: observations and WRF-Chem modeling for the MIRAGE-Shanghai field campaign

2013 ◽  
Vol 13 (11) ◽  
pp. 5655-5669 ◽  
Author(s):  
X. Tie ◽  
F. Geng ◽  
A. Guenther ◽  
J. Cao ◽  
J. Greenberg ◽  
...  
Keyword(s):  
Urban Area ◽  
Air Pollutants ◽  
Regional Scale ◽  
Threshold Value ◽  
Sensitivity Study ◽  
Ozone Production ◽  
Ozone Formation ◽  
Limited Condition ◽  
Ozone Concentrations ◽  
Regional Area

Abstract. The MIRAGE-Shanghai experiment was designed to characterize the factors controlling regional air pollution near a Chinese megacity (Shanghai) and was conducted during September 2009. This paper provides information on the measurements conducted for this study. In order to have some deep analysis of the measurements, a regional chemical/dynamical model (version 3 of Weather Research and Forecasting Chemical model – WRF-Chemv3) is applied for this study. The model results are intensively compared with the measurements to evaluate the model capability for calculating air pollutants in the Shanghai region, especially the chemical species related to ozone formation. The results show that the model is able to calculate the general distributions (the level and the variability) of air pollutants in the Shanghai region, and the differences between the model calculation and the measurement are mostly smaller than 30%, except the calculations of HONO (nitrous acid) at PD (Pudong) and CO (carbon monoxide) at DT (Dongtan). The main scientific focus is the study of ozone chemical formation not only in the urban area, but also on a regional scale of the surrounding area of Shanghai. The results show that during the experiment period, the ozone photochemical formation was strongly under the VOC (volatile organic compound)-limited condition in the urban area of Shanghai. Moreover, the VOC-limited condition occurred not only in the city, but also in the larger regional area. There was a continuous enhancement of ozone concentrations in the downwind of the megacity of Shanghai, resulting in a significant enhancement of ozone concentrations in a very large regional area in the surrounding region of Shanghai. The sensitivity study of the model suggests that there is a threshold value for switching from VOC-limited condition to NOx (nitric oxide and nitrogen dioxide)-limited condition. The threshold value is strongly dependent on the emission ratio of NOx / VOCs. When the ratio is about 0.4, the Shanghai region is under a strong VOC-limited condition over the regional scale. In contrast, when the ratio is reduced to about 0.1, the Shanghai region is under a strong NOx-limited condition. The estimated threshold value (on the regional scale) for switching from VOC-limited to NOx-limited condition ranges from 0.1 to 0.2. This result has important implications for ozone production in this region and will facilitate the development of effective O3 control strategies in the Shanghai region.

scholarly journals Megacity impacts on regional ozone formation: observations and WRF-Chem modeling for the MIRAGE-Shanghai field campaign

2013 ◽  
Vol 13 (1) ◽  
pp. 1673-1716
Author(s):  
X. Tie ◽  
F. Geng ◽  
A. Guenther ◽  
J. Cao ◽  
J. Greenberg ◽  
...  
Keyword(s):  
Urban Area ◽  
Air Pollutants ◽  
Regional Scale ◽  
Threshold Value ◽  
Sensitivity Study ◽  
Ozone Production ◽  
Ozone Formation ◽  
Limited Condition ◽  
Ozone Concentrations ◽  
Regional Area

Abstract. The MIRAGE-Shanghai experiment was designed to characterize the factors controlling regional air pollution near a Chinese Megacity (Shanghai) and was conducted during September 2009. This paper provides an overview of the measurements conducted for this study. In addition to the measurements, a regional chemical/dynamical model (version 3 of Weather Research and Forecasting Chemical model – WRF-Chemv3) is applied for this study. The model results are intensively compared with the measurements to evaluate the model capability for calculating air pollutants in the Shanghai region, especially the chemical species related to ozone formation. The results show that the model is able to calculate the general distributions (the level and the variability) of air pollutants in the Shanghai region, and the difference between the model calculation and the measurement are mostly smaller than 30%, except the calculations of HONO at PD (Pudong) and CO at DT (Dongtan). The main scientific focus is the study of ozone chemical formation not only in the urban area, but also on a regional scale of the surrounding area of Shanghai. The results show that during the experiment period, the ozone photochemical formation was strongly under the VOC-limited condition in the urban area of Shanghai. Moreover, the VOC-limited condition occurred not only in the city, but also in the larger regional area. There was a continuous enhancement of ozone concentrations in the downwind of the megacity of Shanghai, resulting in a significant enhancement of ozone concentrations in a very large regional area in the surrounding region of Shanghai. The sensitivity study of the model suggests that there is a threshold value for switching from VOC-limited condition to NOx-limited condition. The threshold value is strongly dependent on the emission ratio of NOx/VOCs. When the ratio is about 0.4, the Shanghai region is under a strong VOC-limited condition over the regional scale. In contrast, when the ratio is reduced to about 0.1, the Shanghai region is under a strong NOx-limited condition. The estimated threshold value (on the regional scale) for switching from VOC-limited to NOx-limited condition ranges from 0.1 to 0.2. This result has important implications for ozone production in this region and will facilitate the development of effective O3 control strategies in the Shanghai region.

Urban core-downwind differences and relationships related to ozone production in a major urban area in Texas

2021 ◽  
pp. 118624
Author(s):  
Fangzhou Guo ◽  
Alexander A.T. Bui ◽  
Benjamin C. Schulze ◽  
Subin Yoon ◽  
Sujan Shrestha ◽  
...  
Keyword(s):  
Urban Area ◽  
Ozone Production ◽  
Urban Core

scholarly journals Impact of a new condensed toluene mechanism on air quality model predictions in the US

2010 ◽  
Vol 3 (4) ◽  
pp. 2291-2314
Author(s):  
G. Sarwar ◽  
K. W. Appel ◽  
A. G. Carlton ◽  
R. Mathur ◽  
K. Schere ◽  
...  
Keyword(s):  
Air Quality ◽  
Los Angeles ◽  
Production Efficiency ◽  
Sensitivity Study ◽  
Chemical Mechanism ◽  
Ozone Production ◽  
Daily Maximum ◽  
Air Quality Model ◽  
Quality Model ◽  
Mixing Ratios

Abstract. A new condensed toluene mechanism is incorporated into the Community Multiscale Air Quality Modeling system. Model simulations are performed using the CB05 chemical mechanism containing the existing (base) and the new toluene mechanism for the western and eastern US for a summer month. With current estimates of tropospheric emission burden, the new toluene mechanism increases monthly mean daily maximum 8-h ozone by 1.0–3.0 ppbv in Los Angeles, Portland, Seattle, Chicago, Cleveland, northeastern US, and Detroit compared to that with the base toluene chemistry. It reduces model mean bias for ozone at elevated observed ozone mixing ratios. While the new mechanism increases predicted ozone, it does not enhance ozone production efficiency. Sensitivity study suggests that it can further enhance ozone if elevated toluene emissions are present. While changes in total fine particulate mass are small, predictions of in-cloud SOA increase substantially.

scholarly journals Contribution of Local and Transboundary Air Pollution to the Urban Air Quality of Fukuoka, Japan

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 431
Author(s):  
Ayako Yoshino ◽  
Akinori Takami ◽  
Keiichiro Hara ◽  
Chiharu Nishita-Hara ◽  
Masahiko Hayashi ◽  
...  
Keyword(s):  
Air Pollution ◽  
Air Quality ◽  
Urban Areas ◽  
Air Pollutants ◽  
Regional Scale ◽  
Gaseous Species ◽  
Transboundary Air Pollution ◽  
Local Air Pollution ◽  
The City

Transboundary air pollution (TAP) and local air pollution (LAP) influence the air quality of urban areas. Fukuoka, located on the west side of Japan and affected by TAP from the Asian continent, is a unique example for understanding the contribution of LAP and TAP. Gaseous species and particulate matter (PM) were measured for approximately three weeks in Fukuoka in the winter of 2018. We classified two distinctive periods, LAP and TAP, based on wind speed. The classification was supported by variations in the concentration of gaseous species and by backward trajectories. Most air pollutants, including NOx and PM, were high in the LAP period and low in the TAP period. However, ozone was the exception. Therefore, our findings suggest that reducing local emissions is necessary. Ozone was higher in the TAP period, and the variation in ozone concentration was relatively small, indicating that ozone was produced outside of the city and transported to Fukuoka. Thus, air pollutants must also be reduced at a regional scale, including in China.

scholarly journals Benzene and Toluene in the surface air of North Eurasia from TROICA-12 campaign along the Trans-Siberian railway

2016 ◽  
Author(s):  
Andrey I. Skorokhod ◽  
Elena V. Berezina ◽  
Konstantin B. Moiseenko ◽  
Nikolai F. Elansky ◽  
Igor B. Belikov
Keyword(s):  
Motor Vehicle ◽  
Regional Scale ◽  
Proton Transfer Reaction ◽  
Urban Atmosphere ◽  
Ozone Production ◽  
Anthropogenic Sources ◽  
Total Contribution ◽  
South Siberia ◽  
Ozone Photochemistry ◽  
Anthropogenic Pollutant

Abstract. Volatile organic compounds (VOCs) were measured by proton transfer reaction – mass spectrometry (PTR-MS) on a mobile laboratory in a transcontinental TROICA-12 (21.07.2008–04.08.2008) campaign along the Trans-Siberian railway from Moscow to Vladivostok. Surface concentrations of benzene (C6H6) and toluene (C7H8) along with non-methane hydrocarbons (NMHCs), CO, O3, SO2, NO, NO2 and meteorology are analyzed in this study to identify the main sources of benzene and toluene along the Trans-Siberian railway. The most measurements in the TROICA-12 campaign were conducted under low-wind/stagnant conditions in moderately (~ 78 % of measurements) to weakly polluted (~ 20 % of measurements) air directly affected by regional anthropogenic sources adjacent to the railroad. Only 2 % of measurements were identified as characteristic of highly polluted urban atmosphere. Maximum values of benzene and toluene during the campaign reached 36.5 ppb and 45.6 ppb, correspondingly, which is significantly less than their one-time maximum permissible concentrations (94 and 159 ppb for benzene and toluene, correspondingly). About 90 % of benzene and 65 % of toluene content is attributed to motor vehicle transport and 10 % and 20 %, correspondingly, provided by the other local and regional-scale sources. The highest average concentrations of benzene and toluene are measured in the industrial regions of the European Russia (up to 0.3 and 0.4 ppb for benzene and toluene, correspondingly) and south Siberia (up to 0.2 and 0.4 ppb for benzene and toluene, correspondingly). Total contribution of benzene and toluene to photochemical ozone production along the Trans-Siberian railway is about 16 % compared to the most abundant biogenic VOC – isoprene. This contribution, however, is found to be substantially higher (up to 60–70 %) in urbanized areas along the railroad suggesting important role of anthropogenic pollutant sources in regional ozone photochemistry and air quality.

scholarly journals Observations of air composition in Brazil between the Equator and 20°s during the dry season.

1985 ◽  
Vol 15 (1-2) ◽  
pp. 77-120 ◽  
Author(s):  
P.J. Crutzen ◽  
M.T. Coffey ◽  
A.C. Delany ◽  
J. Greenberg ◽  
P. Haagenson ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Carbon Monoxide ◽  
Tropical Forests ◽  
Air Pollutants ◽  
Trace Gases ◽  
Dry Season ◽  
Photochemical Reactions ◽  
Ozone Concentrations ◽  
Air Chemistry ◽  
High Concentrations

Field measurement programs in Brazil during the dry season months of August and September in 1979 and 1980 have demonstrated the great importance of the continental tropics in global air chemistry. Especially in the mixed layer, the air composition over land is much different from that over the ocean and the land areas are clearly longe scale sources of many inportant trace gases. During the dry season much biomass, burning takes place especially in the cerrado regions leading to substantial emission of air pollutants, such as CO, NOx, N2O, CH4 and other hydrocarbons. Ozone concentrations are alsoenhanced due to photochemical reactions. Biogenic organic emissions from tropical forests play likewise an important role in the photochemistry of the atmosphere. Carbon monoxide was found to be present in high concentrations in the boundary layer of the tropical forest, but ozone concentrations were much lower than in the cerrado.

scholarly journals Separating precipitation and evapotranspiration from noise – a new filter routine for high resolution lysimeter data

2013 ◽  
Vol 10 (12) ◽  
pp. 14645-14674 ◽  
Author(s):  
A. Peters ◽  
T. Nehls ◽  
H. Schonsky ◽  
G. Wessolek
Keyword(s):  
Moving Average ◽  
Heavy Precipitation ◽  
Threshold Value ◽  
Sensitivity Study ◽  
Small Data ◽  
Strong Wind ◽  
Weight Changes ◽  
Atmospheric Sciences ◽  
Window Width ◽  
Real Mass

Abstract. Weighing lysimeters yield the most precise and realistic measures for evapotranspiration (ET) and precipitation (P), which are of great importance for many questions regarding soil and atmospheric sciences. An increase or a decrease of the system mass (lysimeter plus seepage) indicate P or ET. These real mass changes of the lysimeter system have to be separated from measurement noise (e.g. caused by wind). The typical way to filter noisy lysimeter data is (i) to introduce a smoothing routine, like a moving average with a certain averaging window w, and then (ii) to apply a certain threshold value δ, accounting for measurement accuracy, separating significant from insignificant weight changes. Thus, two filter parameters are used, namely w and δ. Especially the time variable noise due to wind and strong signals due to heavy precipitation pose challenges for such noise reduction algorithms. If w is too small, data noise might be interpreted as real system changes. If w is too wide, small weight changes in short time intervals might be disregarded. The same applies to too small or too large values for δ. Application of constant w and δ lead either to unnecessary losses of accuracy or to faulty data due to noise. The aim of this paper is to solve that problem with a new filter routine, which is appropriate for any event, ranging from smooth evaporation to strong wind and heavy precipitation. Therefore, the new routine uses adaptive w and δ in dependence on signal strength and noise (AWAT – Adaptive Window and Adaptive Threshold filter). The AWAT filter, a moving average filter and the Savitzky–Golay filter with constant w and δ were applied to real lysimeter data comprising the above mentioned events. The AWAT filter was the only filter which could handle the data of all events very well. A sensitivity study shows that the magnitude of the maximum threshold value has practically no influence on the results, so that only the maximum window width must be predefined by the user.

scholarly journals Analysis of a Regional Scale Chemical-Transport Model to Investigate the Potential Capability of Satellites for Identifying a Widespread Air Pollution Event

2017 ◽  
Author(s):  
Jason Welsh ◽  
Jack Fishman
Keyword(s):  
Transport Model ◽  
Regional Scale ◽  
Ozone Production ◽  
Metropolitan Region ◽  
Trace Gas ◽  
Chemical Transport Model ◽  
Satellite Measurements ◽  
Pollution Event ◽  
Surface O3 ◽  
Good Agreement

We use a regional scale photochemical transport model to investigate the surface concentrations and column integrated amounts of ozone (O3) and nitrogen dioxide (NO2) during a pollution event that occurred in the St. Louis metropolitan region in 2012. These trace gases will be two of the primary constituents that will be measured by TEMPO, an instrument on a geostationary platform, which will result in a dataset that has hourly temporal resolution during the daytime and ~4 km spatial resolution. Although air quality managers are most concerned with surface concentrations, satellite measurements provide a quantity that reflects a column amount, which may or may not be directly relatable to what is measured at the surface. The model results provide good agreement with observed surface O3 concentrations, which is the only trace gas dataset that can be used for verification. The model shows that a plume of O3 extends downwind from St. Louis and contains an integrated amount of ozone of ~ 16 DU (1 DU = 2.69 x 1016 mol. cm-2), a quantity that is two to three times lower than what was observed by satellite measurements during two massive pollution episodes in the 1980s. Based on the smaller isolatable emissions coming from St. Louis, this quantity is not unreasonable, but may also reflect the reduction of photochemical ozone production due to the implementation of emission controls that have gone into effect in the past few decades.

scholarly journals Ozone response to emission changes: a modeling study during the MCMA-2006/MILAGRO campaign

2009 ◽  
Vol 9 (6) ◽  
pp. 23419-23463 ◽  
Author(s):  
J. Song ◽  
W. Lei ◽  
N. Bei ◽  
M. Zavala ◽  
B. de Foy ◽  
...  
Keyword(s):  
Control Strategies ◽  
Monitoring Network ◽  
Ambient Air ◽  
Ozone Production ◽  
Daily Maximum ◽  
Chemical Production ◽  
Field Campaign ◽  
Ozone Concentrations ◽  
Urban Core ◽  
Emission Changes

Abstract. The sensitivity of ozone production to precursor emissions was investigated under five different meteorological conditions in the Mexico City Metropolitan Area (MCMA) during the MCMA-2006/MILAGRO field campaign using the gridded photochemical model CAMx driven by observation-nudged WRF meteorology. Precursor emissions were constrained by the comprehensive data from the field campaign and the routine ambient air quality monitoring network. Simulated plume mixing and transport were examined by comparing with measurements from the G-1 aircraft during the campaign. The observed concentrations of ozone precursors and ozone were well reproduced by the model. The effects of reducing precursor emissions on urban ozone production were performed for three representative emission control strategies. A 50% reduction in VOC emissions led to 7 to 22 ppb decrease in daily maximum ozone concentrations, while a 50% reduction in NOx emissions leads to 4 to 21 ppb increase, and 50% reductions in both NOx and VOC emission decrease the daily maximum ozone concentrations up to 10 ppb. These results along with a chemical indicator analysis using the chemical production ratios of H2O2 to HNO3 demonstrate that the MCMA urban core region is VOC-limited for all meteorological episodes, which is consistent with the results from MCMA-2003 field campaign; however the degree of the VOC-sensitivity is higher in the MCMA-2006 due to lower VOC/NOx emission ratio and VOC reactivity. Ozone formation in the surrounding mountain/rural area is mostly NOx-limited, but can be VOC-limited, and the range of the NOx-limited or VOC-limited areas depends on meteorology.

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