scholarly journals Mixing layer height on the North China Plain and meteorological evidence of serious air pollution in southern Hebei

2017 ◽  
Author(s):  
Xiaowan Zhu ◽  
Guiqian Tang ◽  
Jianping Guo ◽  
Bo Hu ◽  
Tao Song ◽  
...  
Keyword(s):  
Growth Rates ◽  
Wind Shear ◽  
North China Plain ◽  
North China ◽  
Mixing Layer ◽  
Spatiotemporal Variability ◽  
Layer Height ◽  
The North ◽  
The North China Plain ◽  
Mixing Layer Height

Abstract. To investigate the spatiotemporal variability of regional mixing layer height (MLH) on the North China Plain (NCP), multi-site and long-term observations of MLH with ceilometers at three inland stations [e.g., Beijing (BJ), Shijiazhuang (SJZ), Tianjin (TJ)] and one coastal site [e.g., Qinhuangdao (QHD)] were conducted from 16 October 2013 to 15 July 2015. The MLH at the inland stations on the NCP were highest in summer and lowest in winter, while the MLH in the coastal area of Bohai was lowest in summer and highest in spring. The regional MLH developed the earliest in summer (at approximately 7:00 LT) and reached the highest growth rates (164.5 m h−1) at approximately 11:00 LT, while in winter, the regional MLH developed much later (at approximately 9:00 LT), with the maximum growth rates (101.8 m h−1) occurring at 11:00 LT. As a typical site in southern Hebei, the annual mean of MLH at SJZ was 464 ± 183 m, which was 15.0 % and 21.9 % lower than that at the BJ (594 ± 183 m) and TJ (546 ± 197 m) stations, respectively. Investigation of radiation and wind shear at NCP revealed that the net radiation was almost consistent on a regional scale, and the lower MLH in southern Hebei was mainly due to the 1.9–2.8-fold higher intensity of wind shear on the northern NCP than in southern Hebei at an altitude of 300–1700 m. Furthermore, the ventilation coefficient and the relative humidity in southern Hebei were 1.1–2.1 times smaller and 13.2–22.1 % higher than that on the northern NCP, respectively. As a result, severe haze pollution occurred much more readily in southern Hebei and the annual means of near-ground PM2.5 concentrations were almost 1.3 times higher than those of the northern areas. Due to the unfavorable weather conditions, industrial capacity should be reduced in southern Hebei, heavily polluting enterprises should be relocated and strong emission reduction measures are required to improve the air quality.

scholarly journals Mixing layer height on the North China Plain and meteorological evidence of serious air pollution in southern Hebei

2018 ◽  
Vol 18 (7) ◽  
pp. 4897-4910 ◽  
Author(s):  
Xiaowan Zhu ◽  
Guiqian Tang ◽  
Jianping Guo ◽  
Bo Hu ◽  
Tao Song ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Mixing Layer ◽  
Weather Conditions ◽  
Spatiotemporal Variability ◽  
Layer Height ◽  
The North ◽  
The North China Plain ◽  
Mixing Layer Height ◽  
Two Parameters

Abstract. To investigate the spatiotemporal variability of the mixing layer height (MLH) on the North China Plain (NCP), multi-site and long-term observations of the MLH with ceilometers at three inland stations (Beijing, BJ; Shijiazhuang, SJZ; Tianjin, TJ) and one coastal site (Qinhuangdao) were conducted from 16 October 2013 to 15 July 2015. The MLH of the inland stations in the NCP were highest in summer and lowest in winter, while the MLH on the coastal area of Bohai was lowest in summer and highest in spring. As a typical site in southern Hebei, the annual mean of the MLH at SJZ was 464 ± 183 m, which was 15.0 and 21.9 % lower than that at the BJ (594 ± 183 m) and TJ (546 ± 197 m) stations, respectively. Investigation of the shear term and buoyancy term in the NCP revealed that these two parameters in southern Hebei were 2.8 times lower and 1.5 times higher than that in northern NCP within 0–1200 m in winter, respectively, leading to a 1.9-fold higher frequency of the gradient Richardson number > 1 in southern Hebei compared to the northern NCP. Furthermore, combined with aerosol optical depth and PM2.5 observations, we found that the pollutant column concentration contrast (1.2 times) between these two areas was far less than the near-ground PM2.5 concentration contrast (1.5 times). Through analysis of the ventilation coefficient in the NCP, the near-ground heavy pollution in southern Hebei mainly resulted from the lower MLH and wind speed. Therefore, due to the importance of unfavorable weather conditions, heavily polluting enterprises should be relocated and strong emission reduction measures should be introduced to improve the air quality in southern Hebei.

The spatial representativeness of mixing layer height observations in the North China Plain

2018 ◽  
Vol 209 ◽  
pp. 204-211 ◽  
Author(s):  
Xiaowan Zhu ◽  
Guiqian Tang ◽  
Feng Lv ◽  
Bo Hu ◽  
Mengtian Cheng ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Mixing Layer ◽  
Layer Height ◽  
The North ◽  
The North China Plain ◽  
Mixing Layer Height

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 Aerosol chemistry and particle growth events at an urban downwind site in the North China Plain

2018 ◽  
Author(s):  
Yingjie Zhang ◽  
Wei Du ◽  
Yuying Wang ◽  
Qingqing Wang ◽  
Haofei Wang ◽  
...  
Keyword(s):  
Growth Rates ◽  
North China Plain ◽  
North China ◽  
Particle Growth ◽  
Early Morning ◽  
Scanning Mobility Particle Sizer ◽  
Average Mass ◽  
The North ◽  
The North China Plain ◽  
Haze Pollution

Abstract. The North China Plain (NCP) has experienced frequent severe haze pollution events in recent years. While extensive measurements have been made in megacities, aerosol sources, processes, and particle growth at urban downwind sites remain less understood. Here, an Aerosol Chemical Speciation Monitor and a Scanning Mobility Particle Sizer, along with a suite of collocated instruments, were deployed at the downwind site of Xingtai, a highly polluted city in the NCP, for real-time measurements of submicron aerosol (PM1) species and particle number size distributions during May and June 2016. The average mass concentration of PM1 was 30.5 (±19.4) μg m−3, which is significantly lower than that during wintertime. Organic aerosols (OA) constituted the major fraction of PM1 (38 %) followed by sulfate (25 %) and nitrate (14 %). Positive matrix factorization with the Multilinear Engine version 2 showed that oxygenated OA (OOA) was the dominant species in OA throughout the study, on average accounting for 78 % of OA, while traffic and cooking emissions both accounted for 11 % of OA. Our results highlight that aerosol particles at the urban downwind site were highly aged and mainly from secondary formation. However, the diurnal cycle also illustrated the substantial influence of urban emissions on downwind sites, which are characterized by similar pronounced early morning peaks for most aerosol species. New particle formation and growth events were also frequently observed (58 % of the time) on both clean and polluted days. Particle growth rates varying from 1.2 to 4.9 nm h−1 were positively related to the condensation sink during periods with high OOA contributions and also to sulfate concentrations during relatively clean periods. Our results showed that sulfate and OOA played important roles in particle growth during clean periods, while OOA was more important than sulfate during polluted events. Further analyses showed that particle growth rates have no clear dependence on air mass trajectories.

An evaluation of the interaction of morning residual layer ozone and mixing layer ozone in rural areas of the North China Plain

2020 ◽  
Vol 236 ◽  
pp. 104788 ◽  
Author(s):  
Xiaowan Zhu ◽  
Zhiqiang Ma ◽  
Yulu Qiu ◽  
Hui Liu ◽  
Quan Liu ◽  
...  
Keyword(s):  
Rural Areas ◽  
North China Plain ◽  
North China ◽  
Mixing Layer ◽  
Residual Layer ◽  
The North ◽  
The North China Plain

scholarly journals Vertical profiles of black carbon measured by a micro-aethalometer in summer in the North China Plain

2016 ◽  
Author(s):  
L. Ran ◽  
Z. Z. Deng ◽  
X. B. Xu ◽  
P. Yan ◽  
W. L. Lin ◽  
...  
Keyword(s):  
Black Carbon ◽  
North China Plain ◽  
North China ◽  
Mixing Layer ◽  
Ground Level ◽  
Early Morning ◽  
Vertical Profiles ◽  
Field Campaign ◽  
The North ◽  
The North China Plain

Abstract. Black carbon (BC) is a dominant absorber in visible spectrum and a potent factor in climatic effects. Vertical profiles of BC were measured using a micro-aethalometer attached to a tethered balloon during the Vertical Observations of trace Gases and Aerosols (VOGA) field campaign, in summer 2014 at a semirural site in the North China Plain (NCP). The diurnal cycle of BC vertical distributions following the evolution of the mixing layer was investigated for the first time in the NCP region. Statistical parameters including identified mixing height (Hm) and average mass concentrations within the mixing layer (Cm) and in free troposphere (Cf) were obtained for a selected dataset of 67 BC vertical profiles. Hm was usually lower than 0.2 km in the early morning and rapidly rose thereafter due to strengthened turbulence. The maximum height of the ML was reached in late afternoon. The top of a full developed ML exceeded 1 km on sunny days in summer, while stayed much lower on cloudy days. The sunset triggered the collapse of the ML and a stable nocturnal boundary layer (NBL) gradually formed. Accordingly, the highest level Cm was found in the early morning and the lowest in the afternoon. In the daytime, BC almost uniformly distributed within the ML and significantly decreased above the ML. During the field campaign, Cm averaged about 5.16±2.49 μg m−3, with a range of 1.12 to 14.49 μg m−3, comparable with observational results in many polluted urban areas. As evening approached, BC gradually built up near the surface and exponentially declined with height. In contrast to the large variability found both in Hm and Cm, Cf stayed relatively unaffected through the day. Cf was less than 10 % of the ground level under clean conditions, while amounted to half of the ground level in some polluted cases. In-situ measurements of BC vertical profiles would hopefully have an important implication for accurately estimating direct radiative forcing by BC and improving the retrieval of aerosol optical properties by remote sensing in this region.

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