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 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 Aircraft measurements of black carbon in the boundary layer over the North China Plain

2018 ◽  
Author(s):  
Delong Zhao ◽  
Mengyu Huang ◽  
Dantong Liu ◽  
Deping Ding ◽  
Ping Tian ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Temperature ◽  
Black Carbon ◽  
Radiative Forcing ◽  
North China Plain ◽  
North China ◽  
Late Spring ◽  
Aircraft Measurements ◽  
The North ◽  
The North China Plain

Abstract. Black carbon aerosol (BC) is the principle absorber to modify the shortwave radiative balance between the lower atmosphere and the surface in polluted environment, which was in-situ characterized by aircraft measurements using a single particle soot photometer (DMT inc., SP2) throughout the boundary layer up to 3 km over the North China Plain around Beijing megacity. The flights were conducted in both hot season (late spring, Apr.–Jun. 2012, surface temperature > 20 °C, 10 flights) and cold season (winter, Dec. 2016, surface temperature  Fcoating,EZ), however showed seasonally different behaviors in terms of core size (MMDPBL > MMDEZ in late spring, but the opposite in winter). These results provide the basis to evaluate the BC direct radiative forcing in the polluted planetary boundary layer over this region and also the indirect forcing of BC by interacting with low-level clouds.

scholarly journals Relationships between the planetary boundary layer height and surface pollutants derived from lidar observations over China

2018 ◽  
Author(s):  
Tianning Su ◽  
Zhanqing Li ◽  
Ralph Kahn
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Negative Correlation ◽  
North China Plain ◽  
North China ◽  
Planetary Boundary Layer Height ◽  
Layer Height ◽  
Boundary Layer Height ◽  
The North ◽  
The North China Plain

Abstract. The frequent occurrence of severe air pollution episodes in China has raised great concerns with the public and scientific communities. Planetary boundary layer height (PBLH) is a key factor in the vertical mixing and dilution of near-surface pollutants. However, the relationship between PBLH and surface pollutants, especially particulate matter (PM) concentration, across the whole of China, is not yet well understood. We investigate this issue at ~ 1500 surface stations using PBLH derived from space-borne and ground-based lidar, and discuss the influence of topography and meteorological variables on the PBLH-PM relationship. A generally negative correlation is observed between PM and the PBLH, albeit varying greatly in magnitude with location and season. Correlations are much weaker over the highlands than plains regions, which may be associated with lower pollution levels and mountain breezes. The influence of horizontal transport on surface PM is considered as well, manifested as a negative correlation between surface PM and wind speed over the whole nation. Strong wind with clean upwind sources plays a dominant role in removing pollutants, and leads to weak PBLH-PM correlation. A ventilation rate is introduced to jointly consider horizontal and vertical dispersion, which has the largest impact on surface pollutant accumulation over the North China Plain. Aerosol absorption feedbacks also appear to affect the PBLH-PM relationship, as revealed via comparing air pollution in Beijing and Hong Kong. Absorbing aerosols in high concentrations likely contribute to the significant PBLH-PM correlation over the North China Plain (e.g., during winter). As major precursor emissions for secondary aerosols, sulfur dioxide, nitrogen dioxide, and carbon monoxide have similar negative responses to increased PBLH, whereas ozone is positively correlated with PBLH over most regions, which may be caused by heterogeneous reactions and photolysis rates.

scholarly journals Insights into particulate matter pollution in the North China Plain during wintertime: Local contribution or regional transport?

2020 ◽  
Author(s):  
Jiarui Wu ◽  
Naifang Bei ◽  
Yuan Wang ◽  
Xia Li ◽  
Suixin Liu ◽  
...  
Keyword(s):  
Air Quality ◽  
Source Apportionment ◽  
North China Plain ◽  
North China ◽  
Regional Transport ◽  
The North ◽  
The North China Plain ◽  
Haze Event ◽  
Non Local ◽  
Local Emissions

Abstract. Accurate identification and quantitative source apportionment of fine particulate matters (PM2.5) provide an important prerequisite for design and implementation of emission control strategies to reduce PM pollution. Therefore, a source-oriented version of the WRF-Chem model is developed in the study to make source apportionment of PM2.5 in the North China Plain (NCP). A persistent and heavy haze event occurred in the NCP from 05 December 2015 to 04 January 2016 is simulated using the model as a case study to quantify PM2.5 contributions of local emissions and regional transport. Results show that local and non-local emissions contribute 36.3 % and 63.7 % of the PM2.5 mass in Beijing during the haze event on average. When Beijing's air quality is excellent or good in terms of hourly PM2.5 concentrations, local emissions dominate the PM2.5 mass with contributions exceeding 50 %. However, when the air quality is severely polluted, the PM2.5 contribution of non-local emissions is around 75 %. The non-local emissions also dominate the Tianjin's air quality, with average PM2.5 contributions exceeding 70 %. The PM2.5 level in Hebei and Shandong is generally controlled by local emissions, but in Henan, local and non-local emissions play an almost equivalent role in the PM2.5 level, except when the air quality is severely polluted, with non-local PM2.5 contributions of over 60 %. Additionally, the primary aerosol species are generally dominated by local emissions with the average contribution exceeding 50%. However, the source apportionment of secondary aerosols shows more evident regional characteristics. Therefore, except cooperation with neighboring provinces to carry out strict emission mitigation measures, reducing primary aerosols constitutes the priority to alleviate PM pollution in the NCP, especially in Beijing and Tianjin.

scholarly journals Impact of the Green Light Program on haze in the North China Plain, China

2019 ◽  
Vol 19 (17) ◽  
pp. 11185-11197 ◽  
Author(s):  
Xin Long ◽  
Xuexi Tie ◽  
Jiamao Zhou ◽  
Wenting Dai ◽  
Xueke Li ◽  
...  
Keyword(s):  
Power Generation ◽  
Emission Reduction ◽  
North China Plain ◽  
North China ◽  
Thermal Power ◽  
Green Light ◽  
Coal Consumption ◽  
The North ◽  
The North China Plain ◽  
Pm2.5 Concentration

Abstract. As the world's largest developing country, China has undergone ever-increasing demand for electricity during the past few decades. In 1996, China launched the Green Light Program (GLP), which became a national energy conservation activity for saving lighting electricity as well as an effective reduction of the coal consumption for power generation. Despite the great success of the GLP, its effects on haze have not been investigated and well understood. This study focused on assessing the potential coal saving induced by the improvement of luminous efficacy, the core of the GLP, and on estimating the consequent effects on the haze in the North China Plain (NCP), where a large number of power plants are located and are often engulfed by severe haze. The estimated potential coal saving induced by the GLP can reach a massive value of 120–323 million tons, accounting for 6.7 %–18.0 % of the total coal consumption for thermal power generation in China. There was a massive potential emission reduction of air pollutants from thermal power generation in the NCP, which was estimated to be 20.0–53.8 Gg for NOx and 6.9–18.7 Gg for SO2 in December 2015. The potential emission reduction induced by the GLP plays important roles in the haze formation, because the NOx and SO2 are important precursors for the formation of particles. To assess the impact of the GLP on haze, sensitivity studies were conducted by applying a regional chemical–dynamical model (WRF-CHEM). The model results suggest that in the case of lower-limit emission reduction, the PM2.5 concentration decreased by 2–5 µg m−3 in large areas of the NCP. In the case of upper-limit emission reduction, there was much more remarkable decrease in PM2.5 concentration (4–10 µg m−3). This study is a good example to illustrate that scientific innovation can induce important benefits for environment issues such as haze.

scholarly journals Modeling study of the 2010 regional haze event in the North China Plain

2015 ◽  
Vol 15 (16) ◽  
pp. 22781-22822 ◽  
Author(s):  
M. Gao ◽  
G. R. Carmichael ◽  
Y. Wang ◽  
P. E. Saide ◽  
M. Yu ◽  
...  
Keyword(s):  
Air Pollutants ◽  
North China Plain ◽  
North China ◽  
Weather Conditions ◽  
Air Pollution Control ◽  
Wind Speeds ◽  
The North ◽  
The North China Plain ◽  
Haze Event ◽  
Regional Haze

Abstract. The online coupled Weather Research and Forecasting-Chemistry (WRF-Chem) model was applied to simulate a haze event that happened in January 2010 in the North China Plain (NCP), and was validated against various types of measurements. The evaluations indicate that WRF-Chem provides reliable simulations for the 2010 haze event in the NCP. This haze event is mainly caused by high emissions of air pollutants in the NCP and stable weather conditions in winter. Secondary inorganic aerosols also played an important role and cloud chemistry had important contributions. Air pollutants outside Beijing contributed about 47.8 % to the PM2.5 levels in Beijing during this haze event, and most of them are from south Hebei, Shandong and Henan provinces. In addition, aerosol feedback has important impacts on surface temperature, Relative Humidity (RH) and wind speeds, and these meteorological variables affect aerosol distribution and formation in turn. In Shijiazhuang, Planetary Boundary Layer (PBL) decreased about 300 m and PM2.5 increased more than 20 μg m-3 due to aerosol feedback. Feedbacks associated to Black Carbon (BC) account for about 50 % of the PM2.5 increases and 50 % of the PBL decreases in Shijiazhuang, indicating more attention should be paid to BC from both air pollution control and climate change perspectives.

scholarly journals Sources of nitrous acid (HONO) in the upper boundary layer and lower free troposphere of the North China Plain: insights from the Mount Tai Observatory

2020 ◽  
Vol 20 (20) ◽  
pp. 12115-12131
Author(s):  
Ying Jiang ◽  
Likun Xue ◽  
Rongrong Gu ◽  
Mengwei Jia ◽  
Yingnan Zhang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitrous Acid ◽  
North China Plain ◽  
North China ◽  
High Elevation ◽  
Free Troposphere ◽  
Radical Chemistry ◽  
The North ◽  
The North China Plain ◽  
Upper Boundary

Abstract. Nitrous acid (HONO) is a significant precursor of atmospheric “detergent” OH radicals and plays a vital role in tropospheric chemistry. The current knowledge about daytime HONO sources is incomplete, and its impact on the tropospheric radical chemistry has not been fully quantified. Existing observational studies of HONO were mostly conducted at the surface, with few efforts focusing on the high-elevation atmosphere. In order to better understand the characteristics and sources of HONO in the upper boundary layer and lower free troposphere, two intensive field observations were carried out at the summit of Mt. Tai (1534 m a.s.l.), the peak of the North China Plain (NCP), in winter 2017 and spring 2018. HONO showed moderate concentration levels (average ± standard deviation: 0.15±0.15 and 0.13±0.15 ppbv), with maximum values of 1.14 and 3.23 ppbv in winter and spring, respectively. Diurnal variation patterns with broad noontime maxima and lower nighttime concentrations were observed during both campaigns, which is distinct from most of the previous studies at the ground level. The Lagrangian particle dispersion model (LPDM, WRF-FLEXPART v3.3) simulations indicated the combined effects of the planetary boundary layer evolution and valley breeze on the daytime HONO peak. A photostationary state (PSS) analysis suggested a strong unknown daytime HONO source with production rates of 0.45±0.25 ppb h−1 in winter and 0.64±0.49 ppb h−1 in spring. Correlation analysis supported the important role of photo-enhanced heterogeneous conversion of NO2 to HONO on the aerosol surface at this high-elevation site. HONO photolysis is the predominant primary source of OH radical and plays a major role in the radical chemistry at Mt. Tai. The model only considering a homogenous HONO source predicted much lower levels of the HOx radicals and atmospheric oxidation capacity than the model constrained with measured HONO data. This study sheds light on the characteristics, sources, chemistry, and impacts of HONO in the upper boundary layer and lower free troposphere in the NCP region.

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