Change in diurnal variations of meteorological variables induced by anthropogenic aerosols over the North China Plain in summer 2008

2015 ◽  
Vol 124 (1-2) ◽  
pp. 103-118 ◽  
Author(s):  
Yi Gao ◽  
Meigen Zhang ◽  
Xiaohong Liu ◽  
Lili Wang
Keyword(s):  
North China Plain ◽  
North China ◽  
Diurnal Variations ◽  
Meteorological Variables ◽  
Anthropogenic Aerosols ◽  
The North ◽  
The North China Plain

scholarly journals Measurement report: Variations in surface SO<sub>2</sub> and NO<sub>x</sub> mixing ratios from 2004 to 2016 at a background site in the North China Plain

2022 ◽  
Author(s):  
Xueli Liu ◽  
Liang Ran ◽  
Weili Lin ◽  
Xiaobin Xu ◽  
Zhiqiang Ma ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Diurnal Variations ◽  
Nox Emission ◽  
Mixing Ratios ◽  
The North ◽  
The North China Plain ◽  
Regional Background ◽  
Long Term Trends

Abstract. Strict air pollution control strategies have been implemented in recent decades in the North China Plain (NCP), previously one of the most polluted regions in the world, and have resulted in considerable changes in emissions of air pollutants. However, little is so far known about the long-term trends of the regional background level of NOx and SO2, along with the increase and decrease processes of regional emissions. In this study, the seasonal and diurnal variations of NOx and SO2 as well as their long-term trends at a regional background station in the NCP were characterized from 2004 to 2016. On average, SO2 and NOx mixing ratios were 5.7 ± 8.4 ppb and 14.2 ± 12.4 ppb, respectively. The seasonal variations in SO2 and NOx mixing ratios showed a similar pattern with a peak in winter and a valley in summer. However, the diurnal variations in SO2 and NOx mixing ratios greatly differed for all seasons, indicating different sources for SO2 and NOx. Overall, the annual mean SO2 exhibited a significant decreasing trend of ‒6.1 % yr−1 (R = −0.84, P < 0.01) from 2004 to 2016, which is very close to −6.3 % yr−1 of the annual SO2 emission in Beijing, and a greater decreasing trend of −7.4 % yr−1 (R = −0.95, P < 0.01) from 2008 to 2016. The annual mean of NOx showed a fluctuating rise of +3.4 % yr−1 (R = 0.38, P = 0.40) from 2005 to 2010, reaching the peak value (16.9 ppb) in 2010, and then exhibited an extremely significant fluctuating downward trend of −4.5 % yr−1 (R = 0.95, P < 0.01) from 2010 to 2016. After 2010, the annual mean NOx mixing ratios correlated significantly (R = 0.94, P < 0.01) with the annual NOx emission in North China. The decreasing rate (−4.8 % yr−1, R = −0.92, P < 0.01) of the annual mean NOx mixing ratios from 2011 to 2016 at SDZ are lower than the one (−8.8 % yr−1, R = −0.94, P < 0.01) for the annual NOx emission in the NCP and (−9.0 % yr−1, R = −0.96, P < 0.01) in Beijing. It indicated that surface NOx mixing ratios at SDZ had weaker influence than SO2 by the emission reduction in Beijing and its surrounding areas in the NCP. The increase in the amount of motor vehicles led to an increase in traffic emissions for NOx. This study supported conclusions from previous studies that the measures taken for controlling NOx and SO2 in the NCP in the past decades were generally successful. However, NOx emission control should be strengthened in the future.

scholarly journals Modeling the feedback between aerosol and meteorological variables in the atmospheric boundary layer during a severe fog–haze event over the North China Plain

2015 ◽  
Vol 15 (8) ◽  
pp. 4279-4295 ◽  
Author(s):  
Y. Gao ◽  
M. Zhang ◽  
Z. Liu ◽  
L. Wang ◽  
P. Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Radiative Forcing ◽  
Numerical Experiments ◽  
North China Plain ◽  
North China ◽  
Meteorological Variables ◽  
The North ◽  
The North China Plain ◽  
Haze Event ◽  
Pm2.5 Concentration

Abstract. The feedback between aerosol and meteorological variables in the atmospheric boundary layer over the North China Plain (NCP) is analyzed by conducting numerical experiments with and without the aerosol direct and indirect effects via a coupled meteorology and aerosol/chemistry model (WRF-Chem). The numerical experiments are performed for the period of 2–26 January 2013, during which a severe fog–haze event (10–15 January 2013) occurred, with the simulated maximum hourly surface PM2.5 concentration of ~600 ug m−3, minimum atmospheric visibility of ~0.3 km, and 10–100 hours of simulated hourly surface PM2.5 concentration above 300 ug m−3 over NCP. A comparison of model results with aerosol feedback against observations indicates that the model can reproduce the spatial and temporal characteristics of temperature, relative humidity (RH), wind, surface PM2.5 concentration, atmospheric visibility, and aerosol optical depth reasonably well. Analysis of model results with and without aerosol feedback shows that during the fog–haze event aerosols lead to a significant negative radiative forcing of −20 to −140 W m−2 at the surface and a large positive radiative forcing of 20–120 W m−2 in the atmosphere and induce significant changes in meteorological variables with maximum changes during 09:00–18:00 local time (LT) over urban Beijing and Tianjin and south Hebei: the temperature decreases by 0.8–2.8 °C at the surface and increases by 0.1–0.5 °C at around 925 hPa, while RH increases by about 4–12% at the surface and decreases by 1–6% at around 925 hPa. As a result, the aerosol-induced equivalent potential temperature profile change shows that the atmosphere is much more stable and thus the surface wind speed decreases by up to 0.3 m s−1 (10%) and the atmosphere boundary layer height decreases by 40–200 m (5–30%) during the daytime of this severe fog–haze event. Owing to this more stable atmosphere during 09:00–18:00, 10–15~January, compared to the surface PM2.5 concentration from the model results without aerosol feedback, the average surface PM2.5 concentration increases by 10–50 μg m−3 (2–30%) over Beijing, Tianjin, and south Hebei and the maximum increase of hourly surface PM2.5 concentration is around 50 (70%), 90 (60%), and 80 μg m−3 (40%) over Beijing, Tianjin, and south Hebei, respectively. Although the aerosol concentration is maximum at nighttime, the mechanism of feedback, by which meteorological variables increase the aerosol concentration most, occurs during the daytime (around 10:00 and 16:00 LT). The results suggest that aerosol induces a more stable atmosphere, which is favorable for the accumulation of air pollutants, and thus contributes to the formation of fog–haze events.

scholarly journals Hygroscopic properties of aerosol particles at high relative humidity and their diurnal variations in the North China Plain

2011 ◽  
Vol 11 (7) ◽  
pp. 3479-3494 ◽  
Author(s):  
P. F. Liu ◽  
C. S. Zhao ◽  
T. Göbel ◽  
E. Hallbauer ◽  
A. Nowak ◽  
...  
Keyword(s):  
Relative Humidity ◽  
North China Plain ◽  
North China ◽  
Aerosol Particles ◽  
Diurnal Variations ◽  
Hygroscopic Growth ◽  
Carbonaceous Particles ◽  
The North ◽  
Hygroscopic Properties ◽  
The North China Plain

Abstract. The hygroscopic properties of submicron aerosol particles were determined at a suburban site (Wuqing) in the North China Plain among a cluster of cities during the period 17 July to 12 August, 2009. A High Humidity Tandem Differential Mobility Analyser (HH-TDMA) instrument was applied to measure the hygroscopic growth factor (GF) at 90%, 95% and 98.5% relative humidity (RH) for particles with dry diameters between 50 and 250 nm. The probability distribution of GF (GF-PDF) averaged over the period shows a distinct bimodal pattern, namely, a dominant more-hygroscopic (MH) group and a smaller nearly-hydrophobic (NH) group. The MH group particles were highly hygroscopic, and their GF was relatively constant during the period with average values of 1.54 ± 0.02, 1.81 ± 0.04 and 2.45 ± 0.07 at 90%, 95% and 98.5% RH (D0 = 100 nm), respectively. The NH group particles grew very slightly when exposed to high RH, with GF values of 1.08 ± 0.02, 1.13 ± 0.06 and 1.24 ± 0.13 respectively at 90%, 95% and 98.5% RH (D0 = 100 nm). The hygroscopic growth behaviours at different RHs were well represented by a single-parameter Köhler model. Thus, the calculation of GF as a function of RH and dry diameter could be facilitated by an empirical parameterization of κ as function of dry diameter. A strong diurnal pattern in number fraction of different hygroscopic groups was observed. The average number fraction of NH particles during the day was about 8%, while during the nighttime fractions up to 20% were reached. Correspondingly, the state of mixing in terms of water uptake varied significantly during a day. Simulations using a particle-resolved aerosol box model (PartMC-MOSAIC) suggest that the diurnal variations of aerosol hygroscopicity and mixing state were mainly caused by the evolution of the atmospheric mixing layer. The shallow nocturnal boundary layer during the night facilitated the accumulation of freshly emitted carbonaceous particles (mainly hydrophobic) near the surface while in the morning turbulence entrained the more aged and more hygroscopic particles from aloft and diluted the NH particles near the surface resulting in a decrease in the fraction of NH particles.

scholarly journals Characteristics of trace gaseous pollutants at a regional background station in Northern China

2009 ◽  
Vol 9 (3) ◽  
pp. 927-936 ◽  
Author(s):  
Z. Y. Meng ◽  
X. B. Xu ◽  
P. Yan ◽  
G. A. Ding ◽  
J. Tang ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Trace Gases ◽  
Northern China ◽  
Diurnal Variations ◽  
Gaseous Pollutants ◽  
The North ◽  
The North China Plain ◽  
Plain Region ◽  
Co Concentrations

Abstract. Measurements of trace gaseous pollutants were taken at the Shangdianzi site, a WMO Global Atmosphere Watch (GAW) background station in Northern China. The results are presented for the period from September 2003 to December 2006. Seasonal and diurnal variations of the O3, NOx, SO2, and CO concentration are characterized and possible causes for them are discussed. The observed levels of the trace gases are comparable to those at some other background sites in polluted regions inside and outside of China. It was shown that the seasonal variation of O3 can change slightly from year to year due to the year-to-year alternation in the meteorological conditions. Higher CO concentrations were observed in some warmer months, particularly in June and July, 2006. Intensive biomass burning in the North China Plain region, in combination with the transport of regional pollution by more frequent southwesterly winds, is believed to be responsible for the elevated CO concentrations. The diurnal variation of O3, with delayed peaking times, suggests that the transport of photochemical aged plume is an important source for O3 at Shangdianzi. The diurnal variations of SO2 in all seasons show higher values during daytime, contradicting the common view. An explanation for this unusual phenomenon is hypothesized. To gain an insight into the impact of transport on the trace gases levels at Shangdianzi, air mass backward trajectories were calculated and analyzed in combination with corresponding pollutant concentrations. The results indicate that the transport of air masses from the North China Plain region and from the major coal mining regions west of Shangdianzi is responsible for the high concentrations of the gaseous pollutants.

scholarly journals Modeling the feedback between aerosol and meteorological variables in the atmospheric boundary layer during a severe fog-haze event over the North China Plain

2015 ◽  
Vol 15 (1) ◽  
pp. 1093-1130 ◽  
Author(s):  
Y. Gao ◽  
M. Zhang ◽  
Z. Liu ◽  
L. Wang ◽  
P. Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Radiative Forcing ◽  
North China Plain ◽  
North China ◽  
Hebei Province ◽  
Meteorological Variables ◽  
The North ◽  
The North China Plain ◽  
Haze Event ◽  
Pm2.5 Concentration

Abstract. The feedback between aerosol and meteorological variables in the atmospheric boundary layer over the North China Plain is analyzed by conducting numerical experiments with and without the aerosol direct and indirect effects via a coupled meteorology and aerosol/chemistry model (WRF-Chem). The numerical experiments are performed for the period 2–26 January 2013, during which a severe fog-haze event (10–15 January 2013) occurred. Comparison of the model results with aerosol feedback against observations indicates that the model can reproduce the spatial and temporal characteristics of temperature, relative humidity (RH), wind, surface PM2.5 concentration, atmospheric visibility, and aerosol optical depth. Comparison of modeling results in the presence and absence of aerosol feedback during the fog-haze event shows that aerosols lead to a significant negative radiative forcing of −20 to −140 W m−2 at the surface and a large positive radiative forcing of 20–120 W m−2 in the atmosphere and induce significant changes in meteorological variables of which the maximum changes occur during 09:00–18:00 LT over urban Beijing and Tianjin, and south Hebei Province: the temperature decreases by 0.8–2.8 °C at the surface and increases by 0.1–0.5 °C at around 925 hPa while the RH increases by about 4–12% at the surface and decreases by 1–6% at around 925 hPa. As a result, the aerosol-induced equivalent potential temperature profile change shows that the atmosphere is much more stable and thus the surface wind speed decreases by up to 0.3 m s−1 (10%) and the atmosphere boundary layer height decreases by 40–200 m (5–30%) during the daytime of this severe fog-haze event. Owing to this more stable atmosphere, during 09:00–18:00, 10–15 January, compared to the surface PM2.5 concentration from the model results without aerosol feedback, the average surface PM2.5 concentration increases by 10–50 μg m−3 (2–30%) over Beijing, Tianjin, and south Hebei province and the maximum increase of hourly surface PM2.5 concentration is around 50 μg m−3 (70%), 90 μg m−3 (60%) and 80 μg m−3 (40%), averaged over Beijing, Tianjin and south Hebei Province, respectively. Although the aerosol concentration is maximum at nighttime, the mechanism of feedback by which meteorological variables increase the aerosol concentration most occurs during the daytime (around 10:00 and 16:00). The results suggest that aerosol induces a more stable atmosphere, which is favorable for the accumulation of air pollutants, and thus contributes to the formation of fog-haze events.

scholarly journals Hygroscopic properties of aerosol particles at high relative humidity and their diurnal variations in the North China Plain

2011 ◽  
Vol 11 (1) ◽  
pp. 2991-3040 ◽  
Author(s):  
P. F. Liu ◽  
C. S. Zhao ◽  
T. Göbel ◽  
E. Hallbauer ◽  
A. Nowak ◽  
...  
Keyword(s):  
Relative Humidity ◽  
North China Plain ◽  
North China ◽  
Aerosol Particles ◽  
Diurnal Variations ◽  
Hygroscopic Growth ◽  
Mixing State ◽  
The North ◽  
Hygroscopic Properties ◽  
The North China Plain

Abstract. The hygroscopic properties of submicron aerosol particles were determined at a suburban site (Wuqing) in the North China Plain among a cluster of cities during the period 17 July to 12 August 2009. A High Humidity Tandem Differential Mobility Analyser (HH-TDMA) instrument was applied to measure the hygroscopic growth factor (GF) at 90%, 95% and 98.5% relative humidity (RH) for particles with dry diameter between 50–250 nm. The probability distribution of GF (GF-PDF) averaged over the period shows a distinct bimodal pattern, namely, a dominant more-hygroscopic (MH) group and a smaller nearly-hydrophobic (NH) group. The MH group particles were highly hygroscopic, and their GF was relatively constant during the period with average values of 1.54±0.02, 1.81±0.04 and 2.45±0.07 at 90%, 95% and 98.5% RH (D0=100 nm), respectively. The NH group particles grew very slightly when exposed to high RH, with GF values of 1.08±0.02, 1.13±0.06 and 1.24±0.13, respectively at 90%, 95% and 98.5% RH (D0=100 nm). The hygroscopic growth behaviours at different RHs were well represented by the hygroscopicity parameter κ with a single-parameter Köhler model. Thus, the calculation of GF as a function of RH and dry diameter could be facilitated by an empirical parameterization of κ as function of dry diameter. A strong diurnal pattern in number fraction of different hygroscopic groups was observed, indicating a diurnal variation of aerosol mixing state and/or chemical composition. The average number fraction of NH particles during the day was about 8%, while during the nighttime fractions up to 20% were reached. Correspondingly, the state of mixing in terms of water uptake varied significantly during a day. The high fraction of NH particles measured during the night denotes a high degree of external mixing of ambient aerosols, while during the day the degree of external mixing decreased. Simulations using a particle-resolved aerosol box model (PartMC-MOSAIC) suggest that the diurnal variations of aerosol hygroscopicity and mixing state were mainly caused by the evolution of the atmospheric mixing layer. The shallow nocturnal boundary layer during the night facilitated the accumulation of freshly emitted carbonaceous particles (mainly hydrophobic) near the surface while in the morning turbulence entrained the more aged and more hygroscopic particles from aloft and diluted the NH particles near the surface resulting in a decrease in the fraction of NH particles.

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