scholarly journals Space borne tropospheric nitrogen dioxide (NO<sub>2</sub>) observations from 2005–2020 over the Yangtze River Delta (YRD), China: variabilities, implications, and drivers

2022 ◽  
Author(s):  
Hao Yin ◽  
Youwen Sun ◽  
Justus Notholt ◽  
Mathias Palm ◽  
Cheng Liu
Keyword(s):  
Yangtze River ◽  
Industrial Structure ◽  
High Energy ◽  
Yangtze River Delta ◽  
Anthropogenic Emission ◽  
Tropospheric No2 ◽  
Increasing Trends ◽  
The Yrd ◽  
The Yangtze River Delta

Abstract. Nitrogen dioxide (NO2) is mainly affected by local emission and meteorology rather than long-range transport. Accurate acknowledge of its long-term variabilities and drivers are significant for understanding the evolutions of economic and social development, anthropogenic emission, and the effectiveness of pollution control measures on regional scale. In this study, we quantity the long-term variabilities and the underlying drivers of NO2 from 2005 to 2020 over the Yangtze River Delta (YRD), one of the most densely populated and highly industrialized city clusters in China, using OMI space borne observations and the multiple linear regression (MLR) model. We have compared the space borne tropospheric results to the surface in-situ data, yielding correlation coefficients of 0.8 to 0.9 over all megacities within the YRD. As a result, the tropospheric NO2 column measurements can be used as representatives of near-surface conditions, and we thus only use ground-level meteorological data for MLR regression. The inter-annual variabilities of tropospheric NO2 vertical column densities (VCDs) from 2005 to 2020 over the YRD can be divided into two stages. The first stage was from 2005 to 2011, which showed overall increasing trends with a wide range of (1.91 ± 1.50) to (6.70 ± 0.10) × 1014 molecules/cm2·yr−1 (p < 0.01) over the YRD. The second stage was from 2011 to 2020, which showed over all decreasing trends of (−6.31 ± 0.71) to (−11.01 ± 0.90) × 1014 molecules/cm2·yr−1 (p < 0.01) over each of the megacities. The seasonal cycles of tropospheric NO2 VCDs over the YRD are mainly driven by meteorology (81.01 % – 83.91 %) except during winter when anthropogenic emission contributions are pronounced (16.09 % – 18.99 %). The inter annual variabilities of tropospheric NO2 VCDs are mainly driven by anthropogenic emission (69.18 % – 81.34 %) except for a few years such as 2018 which are partly attributed to meteorology anomalies (39.07 % – 91.51 %). The increasing trends in tropospheric NO2 VCDs from 2005 to 2011 over the YRD are mainly attributed to high energy consumption associated with rapid economic growth which cause significant increases in anthropogenic NO2 emissions. The decreasing trends in tropospheric NO2 VCDs from 2011 to 2020 over the YRD are mainly attributed to the stringent clean air measures which either adjust high energy industrial structure toward low energy industrial structure or directly reduce pollutant emissions from different industrial sectors.

scholarly journals Significant wintertime PM<sub>2.5</sub> mitigation in the Yangtze River Delta, China from 2016 to 2019: observational constraints on anthropogenic emission controls

2020 ◽  
Author(s):  
Liqiang Wang ◽  
Shaocai Yu ◽  
Pengfei Li ◽  
Xue Chen ◽  
Zhen Li ◽  
...  
Keyword(s):  
Yangtze River ◽  
Emission Control ◽  
Yangtze River Delta ◽  
Control Measures ◽  
Anthropogenic Emissions ◽  
Observational Constraints ◽  
Anthropogenic Emission ◽  
The Yangtze River Delta ◽  
Emission Control Measures

Abstract. Ambient fine particulate matter (PM2.5) mitigation relies strongly on anthropogenic emission control measures, the actual effectiveness of which is challenging to pinpoint owing to the complex synergies between anthropogenic emissions and meteorology. Here, observational constraints on model simulations allow us to derive not only reliable PM2.5 evolution but also accurate meteorological fields. In this study, we isolate meteorological factors to achieve reliable estimates of surface PM2.5 responses to both long-term and emergency emission control measures from 2016 to 2019 over the Yangtze River Delta (YRD), China. The results show that long-term emission control strategies play a crucial role in curbing PM2.5 levels (> 14 μg/m3, 19 %), especially in the megacities and other areas with abundant anthropogenic emissions. The G20 summit hosted in Hangzhou in 2016 provides a unique and ideal opportunity involving the most stringent, even unsustainable, emergency emission control measures. For the winter time periods from 2016 to 2019, the most substantial declines in PM2.5 concentrations (~ 35 μg/m3, ~ 59 %) are thus achieved in Hangzhou and its surrounding areas. The following hotspots also emerge in megacities, especially in Shanghai (32 μg/m3, 51 %), Nanjing (27 μg/m3, 55 %), and Hefei (24 μg/m3, 44 %). Compared to the long-term policies from 2016 to 2019, the emergency emission control measures implemented during the G20 Summit achieve more significant decreases in PM2.5 concentrations (17 μg/m3 and 41 %) over most of the whole domain, especially in Hangzhou (24 μg/m3, 48 %) and Shanghai (21 μg/m3, 45 %). By extrapolation, we derive insight into the magnitude and spatial distributions of PM2.5 mitigation potentials across the YRD, revealing significantly additional rooms for curbing PM2.5 levels.

scholarly journals Urbanization Enhanced Summertime Extreme Hourly Precipitation over the Yangtze River Delta

2020 ◽  
Vol 33 (13) ◽  
pp. 5809-5826 ◽  
Author(s):  
Xiaoling Jiang ◽  
Yali Luo ◽  
Da-Lin Zhang ◽  
Mengwen Wu
Keyword(s):  
Surface Temperature ◽  
Yangtze River ◽  
Late Summer ◽  
Yangtze River Delta ◽  
The Yangtze River ◽  
Rapid Urbanization ◽  
Hourly Precipitation ◽  
Increasing Trends ◽  
The Yrd ◽  
The Yangtze River Delta

AbstractAn extensive urban agglomeration has occurred over the Yangtze River delta (YRD) region of East China as a result of rapid urbanization since the middle 1990s. In this study, a 44-yr (i.e., 1975–2018) climatology of the summertime extreme hourly precipitation (EXHP; greater than the 90th percentile) over the YRD is analyzed, using historical land-use data, surface temperature, and hourly rain gauge observations, and then the relationship between rapid urbanization and EXHP changes is examined. Results show significant EXHP contrasts in diurnal variation and storm type roughly before and after middle July. That is, tropical cyclones (TCs) account for 16.4% of the total EXHP hours, 80.5% of which occur during the late summer, whereas non-TC EXHP accounts for 94.7% and 66.2% during the early and late summer, respectively. Increasing trends in occurrence frequency and amount of the non-TC and TC-induced EXHP are detected over the urban agglomeration. Statistically significant larger increasing trends in both the EXHP and surface temperature are observed at urban stations than those at the nearby rural stations. An analysis of 113 locally developed non-TC extreme rainfall events during 2011–18 summers also suggests the contribution of the urban heat island effects to the more occurrences of EXHP, especially over a band-shaped urban region where several major cities are distributed. This study reveals a significant correlation between rapid urbanization and increased EXHP during the past two decades over the YRD region. The results have important implications for understanding the impact of urbanization on EXHP changes in a warming climate.

scholarly journals Measurement report: Long-term variations in surface NO<sub>x</sub> and SO<sub>2</sub> from 2006 to 2016 at a background site in the Yangtze River Delta region, China

2021 ◽  
Author(s):  
Qingqing Yin ◽  
Qianli Ma ◽  
Weili Lin ◽  
Xiaobin Xu ◽  
Jie Yao
Keyword(s):  
Yangtze River ◽  
Yangtze River Delta ◽  
Mixing Ratio ◽  
So2 Emissions ◽  
Annual Average ◽  
Mixing Ratios ◽  
The Yrd ◽  
The Yangtze River Delta ◽  
Long Term Variations

Abstract. China has been experiencing rapid changes in emissions of air pollutants in recent decades. Increased emissions of primary particulates and reactive gases caused severe haze in several polluted regions including the Yangtze River Delta (YRD). Measures implemented in recent years for improving air quality have reduced the emissions of NOX, SO2, etc. The emission changes of these gases are reflected by tropospheric columns from satellite observations and surface measurements of surface concentrations from urban sites. However, little is known about the long-term variations in regional background NOX and SO2. In this study, we present NOX and SO2 measurements from the Lin'an station (LAN, 119°44' E,30°18' N,138.6 m a.s.l.), one of the Global Atmosphere Watch (GAW) stations in China. We characterize the seasonal and diurnal variations and study the long-term trends of NOX and SO2 mixing ratios observed at LAN from 2006 to 2016. We also interpret the observed variations and trends in term of changes in meteorological conditions as well as emission of these gases. The overall average mixing ratios of NOX and SO2 during 2006–2016 were 13.6 ± 1.2 ppb and 7.0 ± 4.2 ppb, respectively. The averaged seasonal variations showed maximum values of NOx and SO2 in December (23.5 ± 4.4 ppb) and January (11.9 ± 6.2 ppb), respectively, and minimum values of 7.1 ± 0.8 ppb and 2.8 ± 2.3 ppb (both in July), respectively. The average diurnal variation characteristics of NOX and SO2 differed considerably from each other though the daily average mixing ratios of both gases were significantly correlated (R2 = 0.29, P < 0.001). The annual average mixing ratio of NOX increased during 2006–2011 and then decreased significantly at 0.78 ppb/yr (−5.16 %/yr, P < 0.01). The annual 95 % and 5 % percentiles of hourly NOX mixing ratios showed upward trends until 2012 and 2014, respectively, before a clear decline. The annual average mixing ratio of SO2 decreased significantly at 0.99 ppb/yr (−8.27 %/yr, P < 0.01) from 2006–2016. The annual 95 % and 5 % percentiles of hourly SO2 mixing ratios all exhibited significant (P < 0.001) downward trends at 3.18 ppb/yr and 0.19 ppb/yr, respectively. Changes in the total NOX and SO2 emissions as well as the industrial emissions in the YRD region were significantly correlated with the changes in annual NOX and SO2 mixing ratios. The significant decreases in NOX from 2011 to 2016 and SO2 from 2006 to 2016 highlight the effectiveness of relevant control measures on the reduction in NOX and SO2 emissions in the YRD region. A decrease of annual S / N ratio was found, suggesting a better efficacy in the emission reduction of SO2 than NOX. We found gradual changes in average diurnal patterns of NOX and SO2, which could be attributed to increasing contributions of vehicle emissions to NOX and weakening impacts of large sources on the SO2 concentration. This study reaffirms China's success in controlling both NOX and SO2 in the YRD but indicate at the same time a necessity to strengthen the NOX emission control.

scholarly journals Urbanization-induced urban heat island and aerosol effects on climate extremes in the Yangtze River Delta region of China

2017 ◽  
Vol 17 (8) ◽  
pp. 5439-5457 ◽  
Author(s):  
Shi Zhong ◽  
Yun Qian ◽  
Chun Zhao ◽  
Ruby Leung ◽  
Hailong Wang ◽  
...  
Keyword(s):  
Land Cover ◽  
Yangtze River ◽  
Yangtze River Delta ◽  
Heat Island ◽  
Synoptic Conditions ◽  
Synoptic Forcing ◽  
Urban Heat ◽  
Aerosol Effects ◽  
The Yrd ◽  
The Yangtze River Delta

Abstract. The WRF-Chem model coupled with a single-layer urban canopy model (UCM) is integrated for 5 years at convection-permitting scale to investigate the individual and combined impacts of urbanization-induced changes in land cover and pollutant emissions on regional climate in the Yangtze River Delta (YRD) region in eastern China. Simulations with the urbanization effects reasonably reproduced the observed features of temperature and precipitation in the YRD region. Urbanization over the YRD induces an urban heat island (UHI) effect, which increases the surface temperature by 0.53 °C in summer and increases the annual heat wave days at a rate of 3.7 d yr−1 in the major megacities in the YRD, accompanied by intensified heat stress. In winter, the near-surface air temperature increases by approximately 0.7 °C over commercial areas in the cities but decreases in the surrounding areas. Radiative effects of aerosols tend to cool the surface air by reducing net shortwave radiation at the surface. Compared to the more localized UHI effect, aerosol effects on solar radiation and temperature influence a much larger area, especially downwind of the city cluster in the YRD. Results also show that the UHI increases the frequency of extreme summer precipitation by strengthening the convergence and updrafts over urbanized areas in the afternoon, which favor the development of deep convection. In contrast, the radiative forcing of aerosols results in a surface cooling and upper-atmospheric heating, which enhances atmospheric stability and suppresses convection. The combined effects of the UHI and aerosols on precipitation depend on synoptic conditions. Two rainfall events under two typical but different synoptic weather patterns are further analyzed. It is shown that the impact of urban land cover and aerosols on precipitation is not only determined by their influence on local convergence but also modulated by large-scale weather systems. For the case with a strong synoptic forcing associated with stronger winds and larger spatial convergence, the UHI and aerosol effects are relatively weak. When the synoptic forcing is weak, however, the UHI and aerosol effects on local convergence dominate. This suggests that synoptic forcing plays a significant role in modulating the urbanization-induced land-cover and aerosol effects on individual rainfall event. Hence precipitation changes due to urbanization effects may offset each other under different synoptic conditions, resulting in little changes in mean precipitation at longer timescales.

Long-term observations of tropospheric NO2, SO2 and HCHO by MAX-DOAS in Yangtze River Delta area, China

2018 ◽  
Vol 71 ◽  
pp. 207-221 ◽  
Author(s):  
Xin Tian ◽  
Pinhua Xie ◽  
Jin Xu ◽  
Ang Li ◽  
Yang Wang ◽  
...  
Keyword(s):  
Yangtze River ◽  
Yangtze River Delta ◽  
River Delta ◽  
Delta Area ◽  
Tropospheric No2

scholarly journals Integrating Sustainability Assessment into Decoupling Analysis: A Focus on the Yangtze River Delta Urban Agglomerations

2020 ◽  
Vol 12 (19) ◽  
pp. 7872
Author(s):  
Yijia Huang ◽  
Jiaqi Zhang ◽  
Jinqun Wu
Keyword(s):  
Environmental Sustainability ◽  
Yangtze River ◽  
Sustainability Assessment ◽  
Yangtze River Delta ◽  
River Delta ◽  
The Yangtze River ◽  
Urban Agglomerations ◽  
Decoupling Analysis ◽  
The Yrd ◽  
The Yangtze River Delta

Rapid urbanization has led to a growing number of environmental challenges in large parts of China, where the Yangtze River Delta (YRD) urban agglomerations serve as a typical example. To evaluate the relationship between environmental sustainability gaps and urbanization in 26 cities of the YRD, this study revisited the environmental sustainability assessment (ESA) by combining the metrics of environmental footprints and planetary boundaries at the city level, and then integrated the footprint-boundary ESA framework into decoupling analysis. The results demonstrated considerable spatiotemporal heterogeneity in the environmental sustainability of water use, land use, carbon emissions, nitrogen emissions, phosphorus emissions and PM2.5 emissions across the YRD cities during the study period 2007–2017. Decoupling analysis revealed a positive sign that more than half of the 26 cities had achieved the decoupling of each category of environmental sustainability gaps from urbanization since 2014, especially for nitrogen and phosphorus emissions. On the basis of ESA and decoupling analysis, all the cities were categorized into six patterns, for which the optimal pathways towards sustainable development were discussed in depth. Our study will assist policy makers in formulating more tangible and differentiated policies to achieve decoupling between environmental sustainability gaps and urbanization.

scholarly journals Modeling of the anthropogenic heat flux and its effect on regional meteorology and air quality over the Yangtze River Delta region, China

2016 ◽  
Vol 16 (10) ◽  
pp. 6071-6089 ◽  
Author(s):  
Min Xie ◽  
Jingbiao Liao ◽  
Tijian Wang ◽  
Kuanguang Zhu ◽  
Bingliang Zhuang ◽  
...  
Keyword(s):  
Air Quality ◽  
Urban Areas ◽  
Yangtze River ◽  
Yangtze River Delta ◽  
Vertical Movement ◽  
Anthropogenic Heat ◽  
The Yangtze River ◽  
The Yrd ◽  
Surface O3 ◽  
The Yangtze River Delta

Abstract. Anthropogenic heat (AH) emissions from human activities caused by urbanization can affect the city environment. Based on the energy consumption and the gridded demographic data, the spatial distribution of AH emission over the Yangtze River Delta (YRD) region is estimated. Meanwhile, a new method for the AH parameterization is developed in the WRF/Chem model, which incorporates the gridded AH emission data with the seasonal and diurnal variations into the simulations. By running this upgraded WRF/Chem for 2 typical months in 2010, the impacts of AH on the meteorology and air quality over the YRD region are studied. The results show that the AH fluxes over the YRD have been growing in recent decades. In 2010, the annual-mean values of AH over Shanghai, Jiangsu and Zhejiang are 14.46, 2.61 and 1.63 W m−2, respectively, with the high value of 113.5 W m−2 occurring in the urban areas of Shanghai. These AH emissions can significantly change the urban heat island and urban-breeze circulations in the cities of the YRD region. In Shanghai, 2 m air temperature increases by 1.6 °C in January and 1.4 °C in July, the PBLH (planetary boundary layer height) rises up by 140 m in January and 160 m in July, and 10 m wind speed is enhanced by 0.7 m s−1 in January and 0.5 m s−1 in July, with a higher increment at night. The enhanced vertical movement can transport more moisture to higher levels, which causes the decrease in water vapor at ground level and the increase in the upper PBL (planetary boundary layer), and thereby induces the accumulative precipitation to increase by 15–30 % over the megacities in July. The adding of AH can impact the spatial and vertical distributions of the simulated pollutants as well. The concentrations of primary air pollutants decrease near the surface and increase at the upper levels, due mainly to the increases in PBLH, surface wind speed and upward air vertical movement. But surface O3 concentrations increase in the urban areas, with maximum changes of 2.5 ppb in January and 4 ppb in July. Chemical direct (the rising up of air temperature directly accelerates surface O3 formation) and indirect (the decrease in NOx at the ground results in the increase in surface O3) effects can play a significant role in O3 changes over this region. The meteorology and air pollution predictions in and around large urban areas are highly sensitive to the anthropogenic heat inputs, suggesting that AH should be considered in the climate and air quality assessments.

scholarly journals Integrated studies of a regional ozone pollution synthetically affected by subtropical high and typhoon system in the Yangtze River Delta region, China

2016 ◽  
Author(s):  
Lei Shu ◽  
Min Xie ◽  
Tijian Wang ◽  
Pulong Chen ◽  
Yong Han ◽  
...  
Keyword(s):  
Yangtze River ◽  
Western Pacific Subtropical High ◽  
Yangtze River Delta ◽  
River Delta ◽  
Western Pacific ◽  
Subtropical High ◽  
The Yangtze River ◽  
Observational Analysis ◽  
The Yrd ◽  
The Yangtze River Delta

Abstract. Severe high ozone (O3) episodes usually have close relations to synoptic systems. A regional continuous O3 pollution episode is detected over the Yangtze River Delta (YRD) region in China during August 7–12, 2013, in which the O3 concentrations in more than half of the cities exceeding the national air quality standard. The maximum hourly concentration of O3 reaches 167.1 ppb. By means of the observational analysis and the WRF/CMAQ numerical simulation, the characteristics and the essential impact factors of the typical regional O3 pollution is integratedly investigated. The observational analysis shows that the atmospheric subsidence dominated by Western Pacific subtropical high plays a crucial role in the formation of high-level O3. The favorable weather conditions, such as extremely high temperature, low relative humidity and weak wind speed, caused by the abnormal strong subtropical high are responsible for the trapping and the chemical production of O3 in the boundary layer. In addition, when the YRD cities at the front of Typhoon Utor, the periphery circulation of typhoon system can enhance the downward airflows and cause worse air pollution. But when the typhoon system weakens the subtropical high, the prevailing southeasterly surface wind leads to the mitigation of the O3 pollution. The Integrated Process Rate (IPR) analysis incorporated in CMAQ is applied to further illustrate the combined influence of subtropical high and typhoon system in this O3 episode. The results show that the vertical diffusion (VDIF) and the gas-phase chemistry (CHEM) are two major contributors to O3 formation. During the episode, the contributions of VDIF and CHEM to O3 maintain the high values over 10 ppb/h in Shanghai, Hangzhou, and Nanjing. On August 10–11, the cities close to the sea are apparently affected by the typhoon system, with the contribution of VDIF increasing to 28.45 ppb/h in Shanghai and 19.76 ppb/h in Hangzhou. When the YRD region is under the control of the typhoon system, the contribution values of all individual processes decrease to a low level in all cities. These results provide an insight for the O3 pollution synthetically impacted by the Western Pacific subtropical high and the tropical cyclone system.

Sign in / Sign up

Export Citation Format

Share Document