The two-way feedback mechanism between unfavorable  meteorological conditions and cumulative aerosol  pollution in various haze regions of China

Abstract. Accompanied by unfavorable meteorological conditions with stable stratification in various haze regions of China, persistent heavy aerosol pollution episodes (HPEs) lasting more than 3 consecutive days frequently occur, particularly in winter. In the North China Plain (NCP), explosive growth of fine particulate matter smaller than 2.5 µm in diameter (PM2.5), which occurs during some HPES, is dominated by a two-way feedback mechanism between more unfavorable meteorological conditions and cumulative aerosol pollution. However, the existence of a two-way feedback mechanism such as this in other key haze regions in China is uncertain; these regions include the Guanzhong Plain (GZP), the Yangtze River Delta (YRD) region, the Two Lakes Basin (TLB; a large outflow basin connected to Hubei Province and Hunan Province), the Pearl River Delta (PRD) region, the Sichuan Basin (SB), and the Northeast China Plain (NeCP). In this study, using surface PM2.5 and radiation observations, radiosonde observations, and reanalysis data, we observed the existence of a two-way feedback mechanism in the six abovementioned regions. In the SB, this two-way feedback mechanism is weak due to the suppression of cloudy mid-upper layers. In the more polluted NCP, the GZP, and the NeCP, the feedback is more striking than that in the YRD, the TLB, and the PRD. In these regions, the feedback of worsened meteorological conditions on PM2.5 explains 60 %–70 % of the increase in PM2.5 during the cumulative stages (CSs). For each region, the low-level cooling bias becomes increasingly substantial with increasing aerosol pollution and a closer distance to the ground surface. With PM2.5 mass concentrations greater than 400 µg m−3, the near-ground bias exceeded −4 ∘C in Beijing and reached up to approximately −4 ∘C in Xi'an; this result was caused by accumulated aerosol mass to some extent. In addition to the increase in PM2.5 caused by the two-way feedback, these regions also suffer from the regional transport of pollutants, including inter-regional transport in the GZP, trans-regional transport from the NCP to the YRD and the TLB, and southwesterly transport in the NeCP.

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Two-way feedback mechanism between unfavorable meteorological conditions and cumulative aerosol pollution exists in various haze regions of China

10.5194/acp-2018-1077 ◽

2018 ◽

Author(s):

Junting Zhong ◽

Xiaoye Zhang ◽

Yaqiang Wang ◽

Jizhi Wang ◽

Xiaojing Shen ◽

...

Keyword(s):

Ground Surface ◽

Stable Stratification ◽

Yangtze River Delta ◽

Reanalysis Data ◽

Feedback Mechanism ◽

Meteorological Conditions ◽

River Delta ◽

Regional Transport ◽

Aerosol Pollution ◽

The Yrd

Abstract. Accompanied by unfavorable meteorological conditions with stable stratification in various haze regions of China, persistent heavy aerosol pollution episodes lasting more than 3 consecutive days (HPEs) frequently occur, particularly in winter. In the North China Plain (NCP), explosive growth in PM2.5, which occurs in some HPES, is dominated by a two-way feedback mechanism between further worsened unfavorable meteorological conditions and cumulative aerosol pollution. However, whether such a two-way feedback mechanism exists in other key haze regions is uncertain; these regions include the Guanzhong Plain (GZP), the Yangtze River Delta (YRD) region, the Two Lakes Basin (TLB), the Pearl River Delta (PRD) region, the Sichuan Basin (SB), and the Northeast China Plain (NeCP). In this study, using surface PM2.5 and radiation observations, radiosonde observations, and reanalysis data, we observed the existence of a two-way feedback mechanism in the above six regions. In the SB, this two-way feedback mechanism is weak due to the suppression of cloudy mid-upper layers. In the more polluted NCP, the FWRP, and the NeCP, the feedback is more striking than that in the YRD, the TLB, and the PRD. In these regions, the feedback of worsened meteorological conditions on PM2.5 explains 60–70 % of the increase in PM2.5 during the cumulative stages (CSs). For each region, the low-level cooling bias becomes increasingly substantial with aggravating aerosol pollution and a closer distance to the ground surface. With PM2.5 mass concentrations greater than 400 μg m−3, the near-ground bias exceeded −4 ºC in Beijing and reached up to approximately −4 ºC in Xi’an; this result was caused by accumulated aerosol mass to some extent. In addition to the increase in PM2.5 caused by the two-way feedback, these regions also suffer from the regional transport of pollutants, including inter-regional transport in the FWRP, trans-regional transport from the NCP to the YRD and the TLB, and southwesterly transport in the NeCP.

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Supplementary material to "Two-way feedback mechanism between unfavorable meteorological conditions and cumulative aerosol pollution exists in various haze regions of China"

10.5194/acp-2018-1077-supplement ◽

2018 ◽

Author(s):

Junting Zhong ◽

Xiaoye Zhang ◽

Yaqiang Wang ◽

Jizhi Wang ◽

Xiaojing Shen ◽

...

Keyword(s):

Feedback Mechanism ◽

Meteorological Conditions ◽

Aerosol Pollution ◽

Supplementary Material

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Multi-dimensional satellite observations of aerosol properties and aerosol types over three major urban clusters in eastern China

10.5194/acp-2020-1278 ◽

2021 ◽

Author(s):

Yuqin Liu ◽

Tao Lin ◽

Juan Hong ◽

Yonghong Wang ◽

Lamei Shi ◽

...

Keyword(s):

Vertical Distribution ◽

Eastern China ◽

Peak Frequency ◽

Meteorological Conditions ◽

River Delta ◽

Smoke Aerosol ◽

The Yrd ◽

The Vertical Distribution ◽

Aerosol Types ◽

Aerosol Properties

Abstract. Using nine years (2007–2015) of data from passive (MODIS/Aqua) and active (CALIOP/CALIPSO) satellite measurements over China, we investigate (1) the temporal and spatial variation of aerosol properties over the Beijing-Tianjin-Hebei (BTH) region, the Yangtze River Delta (YRD) and the Pearl River Delta (PRD) and (2) the vertical distribution of aerosol types and extinction coefficients for different aerosol optical depth (AOD) and meteorological conditions. The results show the different spatial patterns and seasonal variations of the AOD over the three regions. Annual time series reveal the occurrence of AOD maxima in 2011 over the YRD and in 2012 over the BTH and PRD; thereafter the AOD decreases steadily. Using the CALIOP vertical feature mask, the contributions of different aerosol types to the AOD were analysed: contributions of dust and polluted dust decrease from north to south, contributions of clean ocean, polluted continental, clean continental and smoke aerosol increase from south to north. In the vertical, the peak frequency of occurrence (FO) for each aerosol type depends on region and season and varies with AOD and meteorological conditions. In general, three distinct layers are observed with the peak FO at the surface (clean continental and clean marine aerosol), at ~1 km (polluted dust and polluted continental aerosol) and at ~3 km (smoke aerosol), whereas dust aerosol may occur all over the altitude range considered in this study (from the surface up to 8 km). In this study nighttime CALIOP profiles were used. The comparison with daytime profiles shows substantial differences in the FO profiles with altitude which suggest effects of boundary layer dynamics and aerosol transport on the vertical distribution of aerosol types.

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Impact of Meteorological Conditions on PM2.5 Pollution in China during Winter

Atmosphere ◽

10.3390/atmos9110429 ◽

2018 ◽

Vol 9 (11) ◽

pp. 429 ◽

Cited By ~ 13

Author(s):

Yanling Xu ◽

Wenbo Xue ◽

Yu Lei ◽

Yang Zhao ◽

Shuiyuan Cheng ◽

...

Keyword(s):

Air Quality ◽

Fine Particulate Matter ◽

Yangtze River Delta ◽

Meteorological Conditions ◽

River Delta ◽

Boundary Layer Height ◽

Low Wind Speed ◽

The Pearl River ◽

The Relationship ◽

Pm2.5 Concentration

Fine particulate matter (PM2.5) poses a risk to human health. In January 2017, the PM2.5 pollution in China was severe, and the average PM2.5 concentration had increased by 14.7% compared to that in January 2016. Meteorological conditions greatly influence PM2.5 pollution. The relationship between PM2.5 and meteorological factors was assessed using monitoring data and the Community Multiscale Air Quality modeling system (CMAQ) was used to quantitatively evaluate the impacts of variations of meteorological conditions on PM2.5 pollution. The results indicate that variations of meteorological conditions between January 2017 and January 2016 caused an increase of 13.6% in the national mean concentration of PM2.5. Unlike the Yangtze River Delta (YRD), where meteorological conditions were favorable, unfavorable meteorological conditions (such as low wind speed, high humidity, low boundary layer height and low rainfall) contributed to PM2.5 concentration worsening by 29.7%, 42.6% and 7.9% in the Beijing-Tianjin-Hebei (JJJ) region, the Pearl River Delta (PRD) region and the Chengdu-Chongqing (CYB) region, respectively. Given the significant influence of local meteorology on PM2.5 concentration, more emphasis should be placed on employing meteorological means to improve local air quality.

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Investigating the impact of regional transport on PM<sub>2.5</sub> formation using vertical observation during APEC 2014 Summit in Beijing

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-15451-2016 ◽

2016 ◽

Vol 16 (24) ◽

pp. 15451-15460 ◽

Cited By ~ 28

Author(s):

Yang Hua ◽

Shuxiao Wang ◽

Jiandong Wang ◽

Jingkun Jiang ◽

Tianshu Zhang ◽

...

Keyword(s):

Relative Humidity ◽

Fine Particulate Matter ◽

Ground Level ◽

Meteorological Conditions ◽

Point Sources ◽

Asia Pacific ◽

Rural Site ◽

Regional Transport ◽

Observation Methods ◽

The Impact

Abstract. During the APEC (Asia-Pacific Economic Cooperation) Economic Leaders' 2014 Summit in Beijing, strict regional air emission controls were implemented, providing a unique opportunity to investigate the transport and formation mechanism of fine particulate matter (PM2.5). This study explores the use of vertical observation methods to investigate the influence of regional transport on PM2.5 pollution in Beijing before and during the APEC Summit. Vertical profiles of extinction coefficient, wind, temperature and relative humidity were monitored at a rural site on the border of Beijing and Hebei Province. Three PM2.5 pollution episodes were analyzed. In episode 1 (27 October to 1 November), regional transport accompanied by the accumulation of pollutants under unfavorable meteorological conditions led to the pollution. In episode 2 (2–5 November), pollutants left from episode 1 were retained in the boundary layer of the region for 2 days and then settled down to the surface, leading to an explosive increase of PM2.5. The regional transport of aged aerosols played a crucial role in the heavy PM2.5 pollution. In episode 3 (6–11 November), emissions from large point sources had been controlled for several days while primary emissions from diesel vehicles might have led to the pollution. It is found that ground-level observation of meteorological conditions and air quality could not fully explain the pollution process, while vertical parameters (aerosol optical properties, winds, relative humidity and temperature) improved the understanding of regional transport influence on heavy pollution processes. Future studies may consider including vertical observations to aid investigation of pollutant transport, especially during episodic events of rapidly increasing concentrations.

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Changes in chemical components of aerosol particles in different haze regions in China from 2006 to 2013 and contribution of meteorological factors

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-12935-2015 ◽

2015 ◽

Vol 15 (22) ◽

pp. 12935-12952 ◽

Cited By ~ 73

Author(s):

X. Y. Zhang ◽

J. Z. Wang ◽

Y. Q. Wang ◽

H. L. Liu ◽

J. Y. Sun ◽

...

Keyword(s):

Coal Combustion ◽

Meteorological Factors ◽

Aerosol Particles ◽

Meteorological Conditions ◽

River Delta ◽

Water Soluble ◽

Chemical Components ◽

Chemical Compositions ◽

Aerosol Pollution ◽

Major Chemical

Abstract. Since there have been individual reports of persistent haze–fog events in January 2013 in central-eastern China, questions on factors causing the drastic differences in changes in 2013 from changes in adjacent years have been raised. Changes in major chemical components of aerosol particles over the years also remain unclear. The extent of meteorological factors contributing to such changes is yet to be determined. The study intends to present the changes in daily based major water-soluble constituents, carbonaceous species, and mineral aerosol in PM10 at 13 stations within different haze regions in China from 2006 to 2013, which are associated with specific meteorological conditions that are highly related to aerosol pollution (parameterized as an index called Parameter Linking Aerosol Pollution and Meteorological Elements – PLAM). No obvious changes were found in annual mean concentrations of these various chemical components and PM10 in 2013, relative to 2012. By contrast, wintertime mass of these components was quite different. In Hua Bei Plain (HBP), sulfate, organic carbon (OC), nitrate, ammonium, element carbon (EC), and mineral dust concentrations in winter were approximately 43, 55, 28, 23, 21, and 130 μg m−3, respectively; these masses were approximately 2 to 4 times higher than those in background mass, which also exhibited a decline during 2006 to 2010 and then a rise till 2013. The mass of these concentrations and PM10, except minerals, respectively, increased by approximately 28 to 117 % and 25 % in January 2013 compared with that in January 2012. Thus, persistent haze–fog events occurred in January 2013, and approximately 60 % of this increase in component concentrations from 2012 to 2013 can be attributed to severe meteorological conditions in the winter of 2013. In the Yangtze River Delta (YRD) area, winter masses of these components, unlike HBP, have not significantly increase since 2010; PLAM were also maintained at a similar level without significant changes. In the Pearl River Delta (PRD) area, the regional background concentrations of the major chemical components were similar to those in the YRD, accounting for approximately 60–80 % of those in HBP. Since 2010, a decline has been found for winter concentrations, which can be partially attributable to persistently improving meteorological conditions and emission cutting with an emphasis on coal combustion in this area. In addition to the scattered and centralized coal combustion for heating, burning biomass fuels contributed to the large increase in concentrations of carbonaceous aerosol in major haze regions in winter, except in the PRD. No obvious changes were found for the proportions of each chemical components of PM10 from 2006 to 2013. Among all of the emissions recorded in chemical compositions in 2013, coal combustion was still the largest anthropogenic source of aerosol pollution in various areas in China, with a higher sulfate proportion of PM10 in most areas of China, and OC was normally ranked third. PM10 concentrations increased by approximately 25 % in January of 2013 relative to 2012, which caused persistent haze–fog events in HBP; emissions also reduced by approximately 35 % in Beijing and its vicinity (BIV) in late autumn of 2014, thereby producing the Asia Pacific Economic Cooperation (APEC) blue (extremely good air quality); thus, one can expect that the persistent haze–fog events would be reduced significantly in the BIV, if approx. one-third of the 2013 winter emissions were reduced, which can also be viewed as the upper limit of atmospheric aerosol pollution capacity in this area.

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Multi-dimensional satellite observations of aerosol properties and aerosol types over three major urban clusters in eastern China

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-12331-2021 ◽

2021 ◽

Vol 21 (16) ◽

pp. 12331-12358

Author(s):

Yuqin Liu ◽

Tao Lin ◽

Juan Hong ◽

Yonghong Wang ◽

Lamei Shi ◽

...

Keyword(s):

Vertical Distribution ◽

Meteorological Conditions ◽

River Delta ◽

Frequency Of Occurrence ◽

Smoke Aerosol ◽

The Yrd ◽

The Vertical Distribution ◽

Aerosol Types ◽

Aerosol Properties ◽

Aerosol Type

Abstract. Using 14 years (2007–2020) of data from passive (MODIS/Aqua) and active (CALIOP/CALIPSO) satellite measurements over China, we investigate (1) the temporal and spatial variation of aerosol properties over the Beijing–Tianjin–Hebei (BTH) region, the Yangtze River Delta (YRD), and the Pearl River Delta (PRD) and (2) the vertical distribution of aerosol types and extinction coefficients for different aerosol optical depth (AOD) and meteorological conditions. The results show the different spatial patterns and seasonal variations of the AOD over the three regions. Annual time series reveal the occurrence of AOD maxima in 2011 over the YRD and in 2012 over the BTH and PRD; thereafter the AOD decreases steadily. Using the CALIOP vertical feature mask, the relative frequency of occurrence (rFO) of each aerosol type in the atmospheric column is analyzed: rFOs of dust and polluted dust decrease from north to south; rFOs of clean ocean, polluted continental, clean continental and elevated smoke aerosol increase from north to south. In the vertical, the peak frequency of occurrence (FO) for each aerosol type depends on region and season and varies with AOD and meteorological conditions. In general, three distinct altitude ranges are observed with the peak FO at the surface (clean continental and clean marine aerosol), at ∼1 km (polluted dust and polluted continental aerosol) and at ∼3 km (elevated smoke aerosol), whereas dust aerosol may occur over the whole altitude range considered in this study (from the surface up to 8 km). The designation of the aerosol type in different height ranges may to some extent reflect the CALIOP aerosol type classification approach. Air mass trajectories indicate the different source regions for the three study areas and for the three different altitude ranges over each area. In this study nighttime CALIOP profiles are used. The comparison with daytime profiles shows substantial differences in the FO profiles with altitude, which suggest effects of boundary layer dynamics and aerosol transport on the vertical distribution of aerosol types, although differences due to day–night CALIOP performance cannot be ruled out.

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Changes in chemical components of aerosol particles in different haze regions in China from 2006 to 2013 and contribution of meteorological factors

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-19197-2015 ◽

2015 ◽

Vol 15 (13) ◽

pp. 19197-19238 ◽

Cited By ~ 1

Author(s):

X. Y. Zhang ◽

J. Z. Wang ◽

Y. Q. Wang ◽

H. L. Liu ◽

J. Y. Sun ◽

...

Keyword(s):

Coal Combustion ◽

Meteorological Factors ◽

Aerosol Particles ◽

Meteorological Conditions ◽

River Delta ◽

Water Soluble ◽

Chemical Components ◽

Chemical Compositions ◽

Aerosol Pollution ◽

Major Chemical

Abstract. Since individuals experienced persistent haze-fog events in January 2013 in central-eastern China, questions on factors causing differences in drastic changes in 2013 from those in adjacent years have been raised. Changes in major chemical components of aerosol particles over the years also remain unclear. The extent of meteorological factors contributed to such changes is yet to be determined. The study intends to present the changes in daily-based major water-soluble constituents, carbonaceous species and mineral aerosol in PM10 at 13 stations within different haze regions in China from 2006 to 2013, associated with specific meteorological conditions that are highly related with aerosol pollution (parameterized as an index called "PLAM"). No obvious changes were found in annual mean concentrations of these various chemical components and PM10 in 2013, relative to 2012. By contrast, wintertime mass of these components were quite different, in Hua Bei Plain (HBP), sulfate, OC, nitrate, ammonium, EC, and mineral dust concentrations in winter were approximately 43, 55, 28, 23, 21 and 130 μg m−3, respectively; these masses were approximately two to four times higher than those in background mass, also exhibiting a decline during 2006 to 2010, and then a rise till 2013. The mass of these concentrations and PM10, except mineral, respectively increased by approximately 28 to 117 and 25 % in January 2013 compared with that in January 2012. Thus, persistent haze-fog events occurred in January 2013, and approximately 60 % of this increase in component concentrations from 2012 to 2013 can be attributed to severe meteorological conditions in the winter of 2013. In Yangtzi River Delta (YRD) area, winter masses of these components, unlike HBP, did not significantly increase since 2010; PLAM was also maintained at a similar level without significant changes. In the Pearl River Delta (PRD) area, the regional background concentrations of the major chemical components were similar to those in YRD; accounted approximately 60–80 % of these in HBP. Since 2010, a decline was found for winter concentrations, which can be partially attributable to a persistent bettering meteorological conditions and the emission cutting with an emphasis on coal-combustion in this area. In addition to the scattered and centralized coal-combustion for heating, burning biomass fuel contributed to the large increase in the concentrations of carbonaceous aerosol in major haze regions, except in PRD, in winter. No obvious changes were found for the proportions of each chemical components of PM10 from 2006 to 2013. Among all of the emissions recorded in chemical compositions in 2013, coal-combustion was still the largest anthropogenic source of aerosol pollution in various areas in China, with higher sulphate proportion of PM10 in most areas of China. OC normally ranked the third. PM10 concentration increased by approximately 25 % in January of 2013 relative to 2012 that caused persistent haze-fog events in HBP; emission also reduced by approximately 35 % in Beijing and its vicinity (BIV) in late fall of 2014, thereby producing "APEC" blue; thus one can expect that the persistent haze-fog events would be reduced significantly in the BIV, if ~ one-third of the 2013 winter emission could be reduced, which can also be viewed as the upper limit of atmospheric aerosol pollution capacity in this area.

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Impacts of Consolidation Time on the Critical Hydraulic Gradient of Newly Deposited Silty Seabed in the Yellow River Delta

Journal of Marine Science and Engineering ◽

10.3390/jmse9030270 ◽

2021 ◽

Vol 9 (3) ◽

pp. 270

Author(s):

Meiyun Tang ◽

Yonggang Jia ◽

Shaotong Zhang ◽

Chenxi Wang ◽

Hanlu Liu

Keyword(s):

Yellow River ◽

Yellow River Delta ◽

Hydraulic Gradient ◽

River Delta ◽

Theoretical Formula ◽

The Yellow River ◽

The Yellow River Delta ◽

Critical Hydraulic Gradient ◽

Seepage Flows ◽

The Yrd

The silty seabed in the Yellow River Delta (YRD) is exposed to deposition, liquefaction, and reconsolidation repeatedly, during which seepage flows are crucial to the seabed strength. In extreme cases, seepage flows could cause seepage failure (SF) in the seabed, endangering the offshore structures. A critical condition exists for the occurrence of SF, i.e., the critical hydraulic gradient (icr). Compared with cohesionless sands, the icr of cohesive sediments is more complex, and no universal evaluation theory is available yet. The present work first improved a self-designed annular flume to avoid SF along the sidewall, then simulated the SF process of the seabed with different consolidation times in order to explore the icr of newly deposited silty seabed in the YRD. It is found that the theoretical formula for icr of cohesionless soil grossly underestimated the icr of cohesive soil. The icr range of silty seabed in the YRD was 8–16, which was significantly affected by the cohesion and was inversely proportional to the seabed fluidization degree. SF could “pump” the sediments vertically from the interior of the seabed with a contribution to sediment resuspension of up to 93.2–96.8%. The higher the consolidation degree, the smaller the contribution will be.

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