scholarly journals Role of Atmospheric Circulations on Haze Pollution in December 2016

2017 ◽  
Author(s):  
Zhicong Yin ◽  
Huijun Wang
Keyword(s):  
Surface Wind ◽  
Weather Conditions ◽  
Gulf Of Alaska ◽  
Surface Wind Speed ◽  
Control Measures ◽  
Anthropogenic Emissions ◽  
Small Surface ◽  
Atmospheric Circulations ◽  
Haze Pollution

Abstract. In the east of China, recent haze pollution has been severe and damaging. In addition to anthropogenic emissions, atmospheric circulations and local meteorological conditions were conductive factors. The number of December haze days over North China and the Huanghuai area has increased sharply since 2010 and was greatest in 2016. During 2016, the most aggressive control measures for anthropogenic emissions were executed from 16–21 December, but the most severe haze pollution still occurred, covering approximately 25 % of the land area of China and lasting for 6 days. The atmospheric circulations must play critical roles. The associated atmospheric circulations that were verified by climatic correlation analysis were a weaker East Asia jet stream in the upper troposphere, a positive phase of the East Atlantic/West Russia pattern in the middle troposphere and conductive local weather conditions (lower PBL, small surface wind speed, and abundant moisture) near the surface. The influence of sea surface temperature near the Gulf of Alaska and the subtropical eastern Pacific, snow cover in western Siberia and associated physical processes on haze pollution are also discussed.

scholarly journals Role of atmospheric circulations in haze pollution in December 2016

2017 ◽  
Vol 17 (18) ◽  
pp. 11673-11681 ◽  
Author(s):  
Zhicong Yin ◽  
Huijun Wang
Keyword(s):  
Surface Wind ◽  
Vertical Motion ◽  
Gulf Of Alaska ◽  
Surface Wind Speed ◽  
Control Measures ◽  
Anthropogenic Emissions ◽  
Atmospheric Circulations ◽  
Atmospheric Particulates ◽  
Haze Pollution ◽  
Narrow Space

Abstract. In the east of China, recent haze pollution has been severe and damaging. In addition to anthropogenic emissions, atmospheric circulations and local meteorological conditions were conducive factors. The number of December haze days over North China and the Huanghuai area has increased sharply since 2010 and was greatest in 2016. During 2016, the most aggressive control measures for anthropogenic emissions were implemented from 16 to 21 December, but the most severe haze pollution still occurred, covering approximately 25 % of the land area of China and lasting for 6 days. The atmospheric circulations must play critical roles in the sub-seasonal haze events. Actually, the positive phase of the East Atlantic–West Russia pattern in the middle troposphere strengthened the anomalous anti-cyclone over the NH area that confined vertical motion below. The associated southerly anomalies made the cold air and surface wind speed weaker, but enhanced the humid flow. Thus, the horizontal and vertical dispersion of atmospheric particulates was suppressed and the pollutants gathered within a narrow space. In December 2016, these key indices were strongly beneficial for haze occurrence and combined to result in the severest haze pollution. The influences of the preceding autumn sea surface temperature near the Gulf of Alaska and the subtropical eastern Pacific, October–November snow cover in western Siberia, and associated physical processes on haze pollution are also discussed.

scholarly journals The Strengthening Relationship between Eurasian Snow Cover and December Haze Days in Central North China after the Mid-1990s

2017 ◽  
Author(s):  
Zhicong Yin ◽  
Huijun Wang
Keyword(s):  
Soil Moisture ◽  
Snow Cover ◽  
North China ◽  
Surface Wind ◽  
Surface Radiation ◽  
Radiative Cooling ◽  
Atmospheric Circulations ◽  
Haze Pollution ◽  
The Relationship ◽  
Haze Days

Abstract. The haze pollution in December has become increasingly serious over recent decades and imposes damage on society, ecosystems, and human health. In addition to anthropogenic emissions, climate change and variability were conducive to haze in China. In this study, the relationship between the snow cover over East Europe and West Siberia (SCES) and the number of haze days in December in central North China was analyzed. This relationship significantly strengthened after the mid-1990s, which is attributed to the effective connections between the SCES and the Eurasian atmospheric circulations. During 1998–2016, the SCES significantly influenced the soil moisture and land surface radiation, and then, the combined underlying drivers of enhanced soil moisture and radiative cooling moved the East Asia jet stream northward and induced anomalous, anti-cyclonic circulation over central North China. Modulated by such atmospheric circulations, the local lower boundary layer, the decreased surface wind and the more humid air were conducive to the worsening dispersion conditions and frequent haze occurrences. In contrast, from 1979 to 1997, the linkage between the SCES and soil moisture was negligible. Furthermore, the correlated radiative cooling was distributed narrowly and far from the key area of snow cover. The associated atmospheric circulations with the SCES were not significantly linked with the ventilation conditions over central North China. Consequently, the relationship between the SCES and the number of hazy days in central North China was insignificant before the mid-1990s but has strengthened and has become significant since then.

scholarly journals Does afforestation deteriorate haze pollution in Beijing–Tianjin–Hebei (BTH), China?

2018 ◽  
Author(s):  
Xin Long ◽  
Naifang Bei ◽  
Jiarui Wu ◽  
Xia Li ◽  
Tian Feng ◽  
...  
Keyword(s):  
Forest Cover ◽  
Fine Particles ◽  
Control Strategies ◽  
Surface Wind ◽  
Forecast Model ◽  
Surface Wind Speed ◽  
Satellite Measurements ◽  
Haze Pollution ◽  
The Impact

Abstract. Although aggressive emission control strategies have been implemented recently in the Beijing–Tianjin–Hebei area (BTH), China, pervasive and persistent haze still frequently engulfs the region during wintertime. Afforestation in BTH, primarily concentrated in the Taihang and Yanshan Mountains, has constituted one of the controversial factors exacerbating the haze pollution due to its slowdown of the surface wind speed. We report here an increasing trend of forest cover in BTH during 2001–2013 based on long-term satellite measurements and the impact of the afforestation on the fine particles (PM2.5) level. Simulations using the Weather Research and Forecast model with chemistry reveal that the afforestation in BTH since 2001 generally deteriorates the haze pollution in BTH to some degree, enhancing PM2.5 concentrations by up to 6 % on average. Complete afforestation or deforestation in the Taihang and Yanshan Mountains would increase or decrease the PM2.5 level within 15 % in BTH. Our model results also suggest that implementing a large ventilation corridor system would not be effective or beneficial to mitigate the haze pollution in Beijing.

scholarly journals The carbon dioxide signal from the COVID-19 lock-down

2020 ◽  
Author(s):  
John Reid
Keyword(s):  
Mixed Layer ◽  
Deep Ocean ◽  
Weather Conditions ◽  
Anthropogenic Emissions ◽  
Temporary Reduction ◽  
Local Weather ◽  
Global Carbon ◽  
Insight Into

Abstract Two unintended experiments provide insight into the role of anthropogenic emissions in the global carbon cycle. One was the temporary reduction in emissions during the COVID-19 lock-down. The other was the emission of a radioactive isotope of carbon during the testing of nuclear weapons in the 1950s and the abrupt cessation of these tests in 1963. Together they imply the existence of two distinct reservoirs which exchange carbon with the atmosphere, viz.: the mixed layer and the deep ocean. Exchanges with the former are noisy because they are influenced by sea surface temperature which, in turn, depends on local weather conditions. They completely mask any variations caused by the COVID-19 lock-down. Exchanges with the latter are steady, long-term and uninfluenced by the weather. They result in half the carbon content of the atmosphere and mixed layer being replaced every eleven years.

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

Atmosphere ◽  
2018 ◽  
Vol 9 (7) ◽  
pp. 277 ◽  
Author(s):  
Hongke Cai ◽  
Ke Gui ◽  
Quanliang Chen
Keyword(s):  
Meteorological Factors ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Joint Effect ◽  
Near Surface ◽  
Annual Variations ◽  
Boundary Layer Height ◽  
Haze Pollution ◽  
Increasing Trend

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.

scholarly journals Effectiveness of emission control to reduce PM<sub>2.5</sub> pollution of Central China during winter haze episodes under various potential synoptic controls

2020 ◽  
Author(s):  
Yingying Yan ◽  
Yue Zhou ◽  
Shaofei Kong ◽  
Jintai Lin ◽  
Jian Wu ◽  
...  
Keyword(s):  
Global Analysis ◽  
Surface Wind ◽  
Emission Control ◽  
Central China ◽  
Emission Sources ◽  
Pressure System ◽  
Small Surface ◽  
Haze Pollution ◽  
Synoptic Conditions ◽  
Local Emission

Abstract. Currently solving the severe particle pollution in autumn and winter is the key to further improve the air quality of China. The source contributions and transboundary transport of fine particles (PM2.5) in pollution episodes are closely related to large-scale or synoptic-scale atmospheric circulation. Under different synoptic conditions, how to effectively reduce emissions to control haze pollution is rarely reported. In this study, we classify the synoptic conditions over Central China from 2013 to 2018 by using Lamb-Jenkension method and the NCEP/NCAR FNL operational global analysis data. The effectiveness of emission control to reduce PM2.5 pollution during winter haze episodes under potential synoptic controls is simulated by GEOS-Chem model. Among the ten identified synoptic patterns, four types account for 87 % of the total pollution days. Two typical synoptic modes of them are characterized by small surface wind speed and stable weather conditions/high relative humidity (A/C-type) over Central China due to a high-pressure system/a southwest trough low-pressure system, blocking pollutants dispersion. Sensitivity simulations show that these two heavy pollution processes are mainly contributed by local emission sources with ~82 % for A-type and ~85 % for C-type, respectively. The other two patterns lead to pollution of transportation characteristics affected by northerly/southerly winds (NW/SW-type), carrying air pollution from northern/southern China to Central China. The contribution of pollution transportation from North/South China is 36.9 %/7.6 % of PM2.5 and local emission sources contribute 41 %/69 %. We also estimate the effectiveness of emission reduction in these four typical severe pollution synoptic processes. By only reducing SO2 and NOx emission and not controlling NH3, the enhanced nitrate counteracts the effect of sulfate reduction on PM2.5 mitigations with less than 4% decrease in PM2.5. In addition, to effectively mitigate haze pollution in NW/SW-type synoptic controlled episodes, local emission control actions should be in coordination with regional collaborative actions.

Impacts of the Diurnal Radiation Cycle on the Formation, Intensity, and Structure of Hurricane Edouard (2014)

2016 ◽  
Vol 73 (7) ◽  
pp. 2871-2892 ◽  
Author(s):  
Xiaodong Tang ◽  
Fuqing Zhang
Keyword(s):  
Surface Wind ◽  
Vertical Wind Shear ◽  
Surface Wind Speed ◽  
Mature Stage ◽  
Radiative Cooling ◽  
Moist Convection ◽  
Solar Insolation ◽  
Secondary Eyewall Formation ◽  
Deep Moist Convection

Abstract This work examines the impacts of the diurnally varying radiation cycle on the formation, intensity, structure, and track of Hurricane Edouard (2014) at different stages of its life cycle through convection-permitting simulations. During the formation stage, nighttime destabilization through radiative cooling may promote deep moist convection that eventually leads to the genesis of the storm, while a tropical cyclone fails to develop in the absence of the night phase despite a strong incipient vortex under moderately strong vertical wind shear. The nighttime radiative cooling further enhances the primary vortex before the storm undergoes rapid intensification. Thereafter, the nighttime radiative cooling mainly increases convective activities outside of the primary eyewall that lead to stronger/broader rainbands and larger storm size during the mature stage of the hurricane; there is, however, less impact on the hurricane’s peak intensity in terms of maximum 10-m surface wind speed. The control forecast undergoes distinct secondary eyewall formation during the mature stage of Edouard (as observed), while there is no apparent eyewall replacement cycle as simulated in sensitivity experiments without solar insolation and the moat is narrower in those with switch-on solar insolation at night, suggesting the potential role of the diurnally varying radiative impact.

scholarly journals The strengthening relationship between Eurasian snow cover and December haze days in central North China after the mid-1990s

2018 ◽  
Vol 18 (7) ◽  
pp. 4753-4763 ◽  
Author(s):  
Zhicong Yin ◽  
Huijun Wang
Keyword(s):  
Soil Moisture ◽  
Snow Cover ◽  
North China ◽  
Surface Wind ◽  
Surface Radiation ◽  
Radiative Cooling ◽  
Atmospheric Circulations ◽  
Haze Pollution ◽  
The Relationship ◽  
Haze Days

Abstract. The haze pollution in December has become increasingly serious over recent decades and imposes damage on society, ecosystems, and human health. In addition to anthropogenic emissions, climate change and variability were conducive to haze in China. In this study, the relationship between the snow cover over eastern Europe and western Siberia (SCES) and the number of haze days in December in central North China was analyzed. This relationship significantly strengthened after the mid-1990s, which is attributed to the effective connections between the SCES and the Eurasian atmospheric circulations. During 1998–2016, the SCES significantly influenced the soil moisture and land surface radiation, and then the combined underlying drivers of enhanced soil moisture and radiative cooling moved the the East Asia jet stream northward and induced anomalous, anti-cyclonic circulation over central North China. Modulated by such atmospheric circulations, the local lower boundary layer, the decreased surface wind, and the more humid air were conducive to the worsening dispersion conditions and frequent haze occurrences. In contrast, from 1979 to 1997, the linkage between the SCES and soil moisture was negligible. Furthermore, the correlated radiative cooling was distributed narrowly and far from the key area of snow cover. The associated atmospheric circulations with the SCES were not significantly linked with the ventilation conditions over central North China. Consequently, the relationship between the SCES and the number of hazy days in central North China was insignificant before the mid-1990s but has strengthened and has become significant since then.

scholarly journals Does afforestation deteriorate haze pollution in Beijing–Tianjin–Hebei (BTH), China?

2018 ◽  
Vol 18 (15) ◽  
pp. 10869-10879 ◽  
Author(s):  
Xin Long ◽  
Naifang Bei ◽  
Jiarui Wu ◽  
Xia Li ◽  
Tian Feng ◽  
...  
Keyword(s):  
Forest Cover ◽  
Control Strategies ◽  
Surface Wind ◽  
Forecast Model ◽  
Surface Wind Speed ◽  
Satellite Measurements ◽  
Haze Pollution ◽  
Increasing Trend ◽  
The Impact

Abstract. Although aggressive emission control strategies have been implemented recently in the Beijing–Tianjin–Hebei area (BTH), China, pervasive and persistent haze still frequently engulfs the region during wintertime. Afforestation in BTH, primarily concentrated in the Taihang and Yan Mountains, has constituted one of the controversial factors exacerbating the haze pollution due to its slowdown of the surface wind speed. We report here an increasing trend of forest cover in BTH during 2001–2013 based on long-term satellite measurements and the impact of the afforestation on the fine-particle (PM2.5) level. Simulations using the Weather Research and Forecast model with chemistry reveal that afforestation in BTH since 2001 has generally been deteriorating the haze pollution in BTH to some degree, enhancing PM2.5 concentrations by up to 6 % on average. Complete afforestation or deforestation in the Taihang and Yan Mountains would increase or decrease the PM2.5 level within 15 % in BTH. Our model results also suggest that implementing a large ventilation corridor system would not be effective or beneficial to mitigate the haze pollution in Beijing.

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