Air stagnation and its impact on air quality during winter in Sichuan and Chongqing, southwestern China

Liao, Tingting; Gui, Ke; Jiang, Wanting; Wang, Shigong; Wang, Bihan; Zeng, Zhaoliang; Che, Huizheng; Wang, Yaqiang; Sun, Yifei

doi:10.1016/j.scitotenv.2018.04.122

Cited by 107 publications

(42 citation statements)

References 37 publications

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“…It is found that the SCB is exposed to the air stagnation conditions for approximately half of the year. From 2013 to 2016, the occurrence frequency of air stagnation days in SCB during winter was~77% in SCB [93]. The BLHs in the margins of the basin are lower than those at the center during winter, and the areas with the shallowest PBL are exactly where Chengdu and Chongqing are located [93], leading to an extremely high occurrence frequency of air stagnation and heavy pollution in these two megacities.…”

Section: Sichuan Basinmentioning

confidence: 99%

“…Due to the blocking effects of surrounding terrains, the wind in the SCB is quite weak, especially in the western part [93]. From the clean stage to polluted stage, the wind speed in Chengdu typically shows a substantial decrease [94].…”

Section: Sichuan Basinmentioning

confidence: 99%

“…For example, the stronger northeasterly wind often prevails during the clean period in Chengdu, which carries cleaner air masses from the less polluted areas to the city [94]; while during the polluted period, the wind usually comes from the south of Chengdu, where many industrial cities are located (e.g., Luzhou, Panzhihua), leading to the transport of pollutants and the deterioration of air quality in Chengdu [94]. Moreover, the mountain ranges to the west of Chengdu act as a barrier to the air flow from the east and cause the accumulation of pollutants in front of the mountain [93,95]. In addition to the weak wind, the high RH is also critical to the pollution in the SCB.…”

Section: Sichuan Basinmentioning

confidence: 99%

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Interaction Between Planetary Boundary Layer and PM2.5 Pollution in Megacities in China: a Review

Miao

et al. 2019

Curr Pollution Rep

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116

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Purpose of Review During the past decades, the number and size of megacities have been growing dramatically in China. Most of Chinese megacities are suffering from heavy PM 2.5 pollution. In the pollution formation, the planetary boundary layer (PBL) plays an important role. This review is aimed at presenting the current state of understanding of the PBL-PM 2.5 interaction in megacities, as well as to identify the main gaps in current knowledge and further research needs. Recent Findings The PBL is critical to the formation of urban PM 2.5 pollution at multiple temporal scales, ranging from diurnal change to seasonal variation. For the essential PBL structure/process in pollution, the coastal megacities have different concerns from the mountainous or landlocked megacities. In the coastal cities, the recirculation induced by sea-land breeze can accumulate pollutants, whereas in the valley/basin, the blocking effects of terrains can lead to stagnant conditions and thermal inversion. Within a megacity, although the urbanization-induced land use change can cause thermodynamic perturbations and facilitate the development of PBL, the increases in emissions outweigh this impact, resulting in a net increase of aerosol concentration. Moreover, the aerosol radiative effects can modify the PBL by heating the upper layers and reducing the surface heat flux, suppressing the PBL and exacerbating the pollution. Summary This review presented the PBL-PM 2.5 interaction in 13 Chinese megacities with various geographic conditions and elucidated the critical influencing processes. To further understand the complicated interactions, long-term observations of meteorology and aerosol properties with multi-layers in the PBL need to be implemented.

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Section: Sichuan Basinmentioning

confidence: 99%

Section: Sichuan Basinmentioning

confidence: 99%

Section: Sichuan Basinmentioning

confidence: 99%

See 1 more Smart Citation

Interaction Between Planetary Boundary Layer and PM2.5 Pollution in Megacities in China: a Review

Miao

et al. 2019

Curr Pollution Rep

Self Cite

116

View full text Add to dashboard Cite

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“…This seasonal pattern of HDs shows that winter may be the most polluted season over SCB, which is attributed to the enhanced pollutant emissions produced by both coal burning and vehicle emissions in winter. In addition, the frequent air stagnation events in winter over SCB also contributed largely to the increase in HDs [30,41]. The lowest HDs occurred in summer, which can be explained by stronger wet deposition owing to frequent precipitation and by the favorable atmospheric diffusion conditions, including the increase of wind speed and planetary boundary layer height.…”

Section: Resultsmentioning

confidence: 97%

Changes in Haze Trends in the Sichuan-Chongqing Region, China, 1980 to 2016

2018

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This study analyzed the long-term variations and trends of haze pollution and its relationships with emission and meteorological factors using the haze days (HDs) data derived from surface observation stations in Sichuan-Chongqing (SCC) region during 1980–2016. The results showed that the multi-year mean number of HDs were 68.7 and 4.9 days for the Sichuan-Basin (SCB) and the rest of SCC region, respectively. The seasonally averaged HDs over SCB reached its maximum in winter (34.7 days), followed by autumn (17.0 days) and spring (11.6 days), and with the minimum observed in summer (5.5 days). The inter-annual variations of HDs in 18 main cities revealed that Zigong, Neijiang, and Yibin, which are located in the southern of SCB, have been the most polluted areas over the SCC region in the past decades. A notable increasing trend in annual HDs over the majority of SCC region was found during 1980–1995, then the trend sharply reversed during 1996–2005, while it increased, fluctuating at some cities after 2006. Seasonally, the increased trend in spring and autumn seems to be the strongest during 1980–1995, whereas the decreased trend in spring and winter was stronger than other seasons during 1996–2005. In addition, a remarkable increasing trend was found in winter since 2006. Using correlation analysis between HDs and emission and meteorological factors during different periods, we found that the variability of local precipitation days (PDs), planetary boundary layer height (PBLH), near-surface wind speed (WS), and relatively humidity (RH) play different roles in influencing the haze pollution change during different historical periods. The joint effect of sharp increase of anthropogenic emissions, reduced PDs and WS intensified the haze pollution in SCB during 1980–1995. In contrast, decreased HDs during 1996–2005 are mainly attributable to the reduction of PM2.5 emission and the increase of PDs (especially in winter). In addition, the decrease of PDs is likely to be responsible for the unexpected increase in winter HDs over SCB in the last decade.

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“…Ning et al (2018) studied the impacts of low-pressure systems on air pollution events in northwest Sichuan during winter, and found that a stagnant situation before a low-pressure system benefits the accumulation of pollutants, while, after the low-pressure system, pollutants are likely to be removed by the strengthening wind conditions and the vertical exchange in the atmosphere [30]. Liao et al (2018) also focused on the stagnation effects on southwestern China [31], while Zhang et al (2019) studied Sichuan Basin's terrain effects [32]. Both studies obtain a relationship between pollutants' properties and meteorological factors similar to that obtained by .…”

Section: Discussionmentioning

confidence: 99%

Analysis of a Severe Pollution Episode in December 2017 in Sichuan Province

Zeng

Zheng

2019

Atmosphere

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To analyze a pollution process in Sichuan from 12 December 2017 to 2 January 2018, hourly pollutant data from 90 environmental monitors with surface data and sounding data from 21 meteorological stations were used to determine the sources of pollutants and the correlation between pollution levels and meteorological conditions. The results show that the whole process could be divided into two parts: (1) from 20 December 2017 to 30 December 2017, when, driven by a static stable atmosphere, the Sichuan basin experienced a long-lasting haze episode with an air quality index (AQI) that exceeded 150; and (2) after 30 December 2017, when a Mongolian cyclone developed and brought a large amount of cold air to Sichuan that improved the horizontal and vertical turbulence exchange and removed most of the pollutants. However, the northern part of Sichuan, affected by the cold air that carried dust from Shanxi and Qinghai, suffered an abrupt change in the extent of PM10 that led to an aggravation of this pollution process.

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Air stagnation and its impact on air quality during winter in Sichuan and Chongqing, southwestern China

Cited by 107 publications

References 37 publications

Interaction Between Planetary Boundary Layer and PM2.5 Pollution in Megacities in China: a Review

Interaction Between Planetary Boundary Layer and PM2.5 Pollution in Megacities in China: a Review

Changes in Haze Trends in the Sichuan-Chongqing Region, China, 1980 to 2016

Analysis of a Severe Pollution Episode in December 2017 in Sichuan Province

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