scholarly journals Impact of western Pacific subtropical high on ozone pollution over eastern China

2021 ◽  
Vol 21 (4) ◽  
pp. 2601-2613
Author(s):  
Zhongjing Jiang ◽  
Jing Li ◽  
Xiao Lu ◽  
Cheng Gong ◽  
Lin Zhang ◽  
...  
Keyword(s):  
Land Surface ◽  
Southern China ◽  
Surface Ozone ◽  
Eastern China ◽  
Western Pacific Subtropical High ◽  
Northern China ◽  
Western Pacific ◽  
Subtropical High ◽  
Ozone Pollution ◽  
Chemical Production

Abstract. Surface ozone is a major pollutant in eastern China, especially during the summer season. The formation of surface ozone pollution highly depends on meteorological conditions largely controlled by regional circulation patterns which can modulate ozone concentrations by influencing the emission of the precursors, the chemical production rates, and regional transport. Here we show that summertime ozone pollution over eastern China is distinctly modulated by the variability of the western Pacific subtropical high (WPSH), a major synoptic system that controls the summertime weather conditions of East Asia. Composite and regression analyses indicate that a positive WPSH anomaly is associated with higher than normal surface ozone concentration over northern China but lower ozone over southern China. Stronger than normal WPSH leads to higher temperatures, stronger solar radiation at the land surface, lower relative humidity, and less precipitation in northern China, favoring the production and accumulation of surface ozone. In contrast, all meteorological variables show reverse changes in southern China under a stronger WPSH. GEOS-Chem simulations reasonably reproduce the observed ozone changes associated with the WPSH and support the statistical analyses. We further conduct a budget diagnosis to quantify the detailed contributions of chemistry, transport, mixing, and convection processes. The result shows that chemistry plays a decisive role in leading the ozone changes among these processes. Results show that the changes in ozone are primarily attributed to chemical processes. Moreover, the natural emission of precursors from biogenic and soil sources, a major component influencing the chemical production, accounts for ∼ 30 % of the total surface ozone changes.

scholarly journals Impact of Western Pacific Subtropical High on Ozone Pollution over Eastern China

2020 ◽  
Author(s):  
Zhongjing Jiang ◽  
Jing Li ◽  
Xiao Lu ◽  
Cheng Gong ◽  
Lin Zhang ◽  
...  
Keyword(s):  
Land Surface ◽  
Southern China ◽  
Surface Ozone ◽  
Eastern China ◽  
Decisive Role ◽  
Western Pacific Subtropical High ◽  
Northern China ◽  
Subtropical High ◽  
Ozone Pollution ◽  
Normal Surface

Abstract. Surface ozone is a major pollutant in Eastern China, especially during the summer season. The formation of surface ozone pollution highly depends on meteorological conditions as generally controlled regional circulation patterns. Here we show that summertime ozone pollution over Eastern China is distinctly modulated by the variability of West Pacific Subtropical High (WPSH), a major synoptic system that controls the summertime weather conditions of East Asia. Composite and regression analyses indicate that positive WPSH anomaly is associated with higher than normal surface ozone concentration over Northern China but lower ozone over Southern China. We show that this is mainly driven by changes in meteorological variables with stronger than normal WPSH leading to higher temperatures, stronger solar radiation at the land surface, lower relative humidity, and less precipitation in Northern China, favoring the production and accumulation of surface ozone. In contrast, all variables show reverse changes in Southern China under stronger WPSH. GEOS-Chem simulations reasonably reproduce the observed ozone changes associated with the WPSH and support the statistical analyses. Detailed contributions of different processes are quantified through budget diagnosis, which emphasizes the decisive role of chemistry. Natural emission of precursors from biogenic and soil sources accounts for ~30 % of the total surface ozone changes.

scholarly journals Dominant patterns of summer ozone pollution in eastern China and associated atmospheric circulations

2019 ◽  
Vol 19 (22) ◽  
pp. 13933-13943 ◽  
Author(s):  
Zhicong Yin ◽  
Bufan Cao ◽  
Huijun Wang
Keyword(s):  
North China ◽  
Surface Ozone ◽  
Eastern China ◽  
Western Pacific Subtropical High ◽  
Ground Level ◽  
Photochemical Reactions ◽  
Western Pacific ◽  
Subtropical High ◽  
Ozone Pollution ◽  
Atmospheric Circulations

Abstract. Surface ozone has been severe during summers in the eastern parts of China, damaging human health and flora and fauna. During 2015–2018, ground-level ozone pollution increased and intensified from south to north. In North China and the Huanghuai region, the O3 concentrations were highest. Two dominant patterns of summer ozone pollution were determined, i.e., a south–north covariant pattern and a south–north differential pattern. The anomalous atmospheric circulations composited for the first pattern manifested as a zonally enhanced East Asian deep trough and as a western Pacific subtropical high, whose western ridge point shifted northward. The local hot, dry air and intense solar radiation enhanced the photochemical reactions to elevate the O3 pollution levels in North China and the Huanghuai region; however, the removal of pollutants was decreased. For the second pattern, the broad positive geopotential height anomalies at high latitudes significantly weakened cold air advection from the north, and those extending to North China resulted in locally high temperatures near the surface. In a different manner, the western Pacific subtropical high transported sufficient water vapor to the Yangtze River Delta and resulted in a locally adverse environment for the formation of surface ozone. In addition, the most dominant pattern in 2017 and 2018 was different from that in previous years, which is investigated as a new feature.

scholarly journals Summer High Temperature Extremes over China Linked to the Pacific Meridional Mode

2020 ◽  
Vol 33 (14) ◽  
pp. 5905-5917
Author(s):  
Ming Luo ◽  
Ngar-Cheung Lau ◽  
Wei Zhang ◽  
Qiang Zhang ◽  
Zhen Liu
Keyword(s):  
High Temperature ◽  
Land Surface ◽  
Southern China ◽  
Eastern China ◽  
Northern China ◽  
Temperature Extremes ◽  
The Pacific ◽  
Meridional Mode ◽  
High Temperature Extremes ◽  
Pacific Meridional Mode

AbstractThis study investigates the association between summer high temperature extremes (HTEs) over China and the Pacific meridional mode (PMM) that is characterized by an anomalous north–south sea surface temperature gradient and an anomalous surface circulation over the northeastern subtropical Pacific. It is found that the HTE activities over most parts of southern China (particularly eastern China) are prominently intensified during the positive PMM phase and weakened during the negative phase. Further examinations suggest that the PMM is linked with HTEs in China through processes that entail both eastward and westward development of signals emanating from the PMM site. The westward development is associated with the formation of an anomalous low-level cyclone over the western North Pacific (WNP), which may be viewed as a Matsuno–Gill-type response to the off-equatorial heating in the eastern Pacific. This circulation change is accompanied by anomalous ascent over WNP and northern China, and subsidence over eastern China. On the other hand, the eastward development process is linked to the PMM-induced displacement of the East Asian jet stream and the generation of a midlatitude Rossby wave train. In the positive PMM phase, the above circulation changes are accompanied by anomalous air subsidence and enhanced adiabatic heating, reduced precipitation, anomalous lower-level anticyclone, and rising surface pressure over the eastern part of China. Moreover, the land surface of that region receives more solar radiation. Opposite changes are discernible over northern China. These changes are favorable for the occurrence and persistence of HTEs over eastern China and tend to suppress HTEs over northern China.

scholarly journals Dominant Patterns of Summer Ozone Pollution in Eastern China and Associated Atmospheric Circulations

2019 ◽  
Author(s):  
Zhicong Yin ◽  
Bufan Cao ◽  
Huijun Wang
Keyword(s):  
North China ◽  
Surface Ozone ◽  
Eastern China ◽  
Photochemical Reactions ◽  
Air Pollutant ◽  
Subtropical High ◽  
Ozone Pollution ◽  
West Pacific ◽  
Atmospheric Circulations ◽  
West Pacific Subtropical High

Abstract. Surface ozone, a man-made air pollutant, has been severe during summers in the eastern parts of China, damaging human’s health and flora and fauna. During 2015–2018, ground-level ozone pollution increased year by year and intensified from south to north. In North China and Huanghuai region, the O3 concentrations were highest. Two dominant patterns of summer ozone pollution were determined, i.e., a south-north covariant pattern and a south-north differential pattern. The anomalous atmospheric circulations composited for the first pattern manifested as a zonally enhanced East Asia deep trough and as a west Pacific subtropical high whose western ridge point shifted northward. The local hot, dry air and intense solar radiation enhanced the photochemical reactions to elevate the O3 pollution levels in North China and Huanghuai region. For the second pattern, the broad positive geopotential height anomalies at high latitudes significantly weakened cold air activity, and those extending to North China resulted in locally high temperature near the surface. In a different manner, the west Pacific subtropical high transported sufficient water vapor to the Yangtze River Delta and resulted in locally adverse environment for the formation of surface ozone. Furthermore, the implications for the interannual differences in summer O3 pollution have also proven to be meaningful.

scholarly journals An evaluation of the ability of the Ozone Monitoring Instrument (OMI) to observe boundary layer ozone pollution across China: application to 2005–2017 ozone trends

2019 ◽  
Vol 19 (9) ◽  
pp. 6551-6560 ◽  
Author(s):  
Lu Shen ◽  
Daniel J. Jacob ◽  
Xiong Liu ◽  
Guanyu Huang ◽  
Ke Li ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Tropospheric Ozone ◽  
Southern China ◽  
Surface Ozone ◽  
Eastern China ◽  
Ozone Pollution ◽  
Ozone Monitoring Instrument ◽  
Monitoring Instrument ◽  
Ozone Monitoring ◽  
Boundary Layer Ozone

Abstract. Nadir-viewing satellite observations of tropospheric ozone in the UV have been shown to have some sensitivity to boundary layer ozone pollution episodes, but so far they have not yet been compared to surface ozone observations collected by large-scale monitoring networks. Here we use 2013–2017 surface ozone data from China's new Ministry of Ecology and Environment (MEE) network of ∼ 1000 sites, together with vertical profiles from ozonesondes and aircraft, to quantify the ability of tropospheric ozone retrievals from the Ozone Monitoring Instrument (OMI) and to detect boundary layer ozone pollution in China. We focus on summer when ozone pollution in China is most severe and when OMI has the strongest sensitivity. After subtracting the Pacific background, we find that the 2013–2017 mean OMI ozone enhancements over eastern China have strong spatial correlation with the corresponding multiyear means in the surface afternoon observations (R=0.73), and that OMI can estimate these multiyear means in summer afternoon surface ozone with a precision of 8 ppb. The OMI data show significantly higher values on observed surface ozone episode days (>82 ppb) than on non-episode days. Day-to-day correlations with surface ozone are much weaker due to OMI noise and are stronger for sites in southern China (<34∘ N; R=0.3–0.6) than in northern China (R=0.1–0.3) because of weaker retrieval sensitivity and larger upper tropospheric variability in the north. Ozonesonde data show that much of the variability of OMI ozone over southern China in summer is driven by the boundary layer. Comparison of 2005–2009 and 2013–2017 OMI data indicates that mean summer afternoon surface ozone in southern China (including urban and rural regions) has increased by 3.5±3.0 ppb over the 8-year period and that the number of episode days per summer has increased by 2.2±0.4 (as diagnosed by an extreme value model), generally consistent with the few long-term surface records. Ozone increases have been particularly large in the Yangtze River Delta and in the Hubei, Guangxi and Hainan provinces.

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