scholarly journals Vertically-resolved Characteristics of Air Pollution during Two Severe Winter Haze Episodes in Urban Beijing, China

2017 ◽  
Author(s):  
Qingqing Wang ◽  
Yele Sun ◽  
Weiqi Xu ◽  
Wei Du ◽  
Libo Zhou ◽  
...  
Keyword(s):  
Mixing Layer ◽  
Urban Site ◽  
Formation Mechanisms ◽  
Vertical Profiles ◽  
Severe Winter ◽  
Aerosol Composition ◽  
Layer Height ◽  
Mixing Layer Height ◽  
The Impact ◽  
Beijing China

Abstract. We conducted the first real-time continuous vertical measurements of particle extinction (bext), gaseous NO2, and black carbon (BC) from ground level to 260 m during two severe winter haze episodes at an urban site in Beijing, China. Our results illustrated four distinct types of vertical profiles: 1) uniform vertical distributions (37 % of the time) with vertical differences less than 5 %; 2) higher values at lower altitudes (29 %); 3) higher values at higher altitudes (16 %), and 4) significant decreases at the heights of ~ 100–150 m (14 %). Further analysis demonstrated that vertical convection as indicated by mixing layer height, temperature inversion, and local emissions are three major factors affecting the changes in vertical profiles. Particularly, the formation of Type 4 was strongly associated with the stratified layer that was formed due to the interactions of different air masses and temperature inversions. Aerosol composition was substantially different below and above the transition heights with ~ 20–30 % higher contributions of local sources (e.g., biomass burning and cooking) at lower altitudes. A more detailed evolution of vertical profiles and their relationship with the changes in source emissions, mixing layer height, and aerosol chemistry was illustrated by a case study. BC showed overall similar vertical profiles as those of bext (R2 = 0.92 and 0.69 in November and January, respectively). While NO2 was correlated with bext for most of the time, the vertical profiles of bext/NO2 varied differently for different profiles, indicating the impact of chemical transformation on vertical profiles. Our results also showed that more comprehensive vertical measurements (e.g., more aerosol and gaseous species) at higher altitudes in the megacities are needed for a better understanding of the formation mechanisms and evolution of severe haze episodes in China.

scholarly journals Vertically resolved characteristics of air pollution during two severe winter haze episodes in urban Beijing, China

2018 ◽  
Vol 18 (4) ◽  
pp. 2495-2509 ◽  
Author(s):  
Qingqing Wang ◽  
Yele Sun ◽  
Weiqi Xu ◽  
Wei Du ◽  
Libo Zhou ◽  
...  
Keyword(s):  
Mixing Layer ◽  
Urban Site ◽  
Formation Mechanisms ◽  
Vertical Profiles ◽  
Severe Winter ◽  
Aerosol Composition ◽  
Layer Height ◽  
Mixing Layer Height ◽  
The Impact ◽  
Beijing China

Abstract. We conducted the first real-time continuous vertical measurements of particle extinction (bext), gaseous NO2, and black carbon (BC) from ground level to 260 m during two severe winter haze episodes at an urban site in Beijing, China. Our results illustrated four distinct types of vertical profiles: (1) uniform vertical distributions (37 % of the time) with vertical differences less than 5 %, (2) higher values at lower altitudes (29 %), (3) higher values at higher altitudes (16 %), and (4) significant decreases at the heights of ∼ 100–150 m (14 %). Further analysis demonstrated that vertical convection as indicated by mixing layer height, temperature inversion, and local emissions are three major factors affecting the changes in vertical profiles. Particularly, the formation of type 4 was strongly associated with the stratified layer that was formed due to the interactions of different air masses and temperature inversions. Aerosol composition was substantially different below and above the transition heights with ∼ 20–30 % higher contributions of local sources (e.g., biomass burning and cooking) at lower altitudes. A more detailed evolution of vertical profiles and their relationship with the changes in source emissions, mixing layer height, and aerosol chemistry was illustrated by a case study. BC showed overall similar vertical profiles as those of bext (R2=0.92 and 0.69 in November and January, respectively). While NO2 was correlated with bext for most of the time, the vertical profiles of bext ∕ NO2 varied differently for different profiles, indicating the impact of chemical transformation on vertical profiles. Our results also showed that more comprehensive vertical measurements (e.g., more aerosol and gaseous species) at higher altitudes in the megacities are needed for a better understanding of the formation mechanisms and evolution of severe haze episodes in China.

scholarly journals Lidar-based remote sensing of atmospheric boundary layer height over land and ocean

2014 ◽  
Vol 7 (1) ◽  
pp. 173-182 ◽  
Author(s):  
T. Luo ◽  
R. Yuan ◽  
Z. Wang
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Marine Boundary Layer ◽  
Mixing Layer ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Lidar Measurements ◽  
Mixing Layer Height ◽  
Atmospheric Radiation Measurement ◽  
Atmospheric Boundary Layer Height

Abstract. Atmospheric boundary layer (ABL) processes are important in climate, weather and air quality. A better understanding of the structure and the behavior of the ABL is required for understanding and modeling of the chemistry and dynamics of the atmosphere on all scales. Based on the systematic variations of the ABL structures over different surfaces, different lidar-based methods were developed and evaluated to determine the boundary layer height and mixing layer height over land and ocean. With Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) micropulse lidar (MPL) and radiosonde measurements, diurnal and season cycles of atmospheric boundary layer depth and the ABL vertical structure over ocean and land are analyzed. The new methods are then applied to satellite lidar measurements. The aerosol-derived global marine boundary layer heights are evaluated with marine ABL stratiform cloud top heights and results show a good agreement between them.

scholarly journals Erratum to: Observed and Modelled Convective Mixing-Layer Height at Dome C, Antarctica

2014 ◽  
Vol 153 (1) ◽  
pp. 163-164 ◽  
Author(s):  
Giampietro Casasanta ◽  
Ilaria Pietroni ◽  
Igor Petenko ◽  
Stefania Argentini
Keyword(s):  
Mixing Layer ◽  
Layer Height ◽  
Convective Mixing ◽  
Mixing Layer Height

scholarly journals Estimation of atmospheric mixing layer height from radiosonde data

2014 ◽  
Vol 7 (6) ◽  
pp. 1701-1709 ◽  
Author(s):  
X. Y. Wang ◽  
K. C. Wang
Keyword(s):  
North America ◽  
Potential Temperature ◽  
Mixing Layer ◽  
Specific Humidity ◽  
Radiosonde Data ◽  
Consistent Estimate ◽  
Climate Data ◽  
Layer Height ◽  
Temperature And Humidity ◽  
Mixing Layer Height

Abstract. Mixing layer height (h) is an important parameter for understanding the transport process in the troposphere, air pollution, weather and climate change. Many methods have been proposed to determine h by identifying the turning point of the radiosonde profile. However, substantial differences have been observed in the existing methods (e.g. the potential temperature (θ), relative humidity (RH), specific humidity (q) and atmospheric refractivity (N) methods). These differences are associated with the inconsistency of the temperature and humidity profiles in a boundary layer that is not well mixed, the changing measurability of the specific humidity and refractivity with height, the measurement error of humidity instruments within clouds, and the general existence of clouds. This study proposes a method to integrate the information of temperature, humidity and cloud to generate a consistent estimate of h. We apply this method to high vertical resolution (~ 30 m) radiosonde data that were collected at 79 stations over North America during the period from 1998 to 2008. The data are obtained from the Stratospheric Processes and their Role in Climate Data Center (SPARC). The results show good agreement with those from N method as the information of temperature and humidity contained in N; however, cloud effects that are included in our method increased the reliability of our estimated h. From 1988 to 2008, the climatological h over North America was 1675 ± 303 m with a strong east–west gradient: higher values (generally greater than 1800 m) occurred over the Midwest US, and lower values (usually less than 1400 m) occurred over Alaska and the US West Coast.

Source identification of aerosol chemical composition in the Atlas region of North Africa.

2021 ◽  
Author(s):  
Nabil Deabji ◽  
Khanneh Wadinga Fomba ◽  
Eduardo José dos Santos Souza ◽  
Hartmut Herrmann
Keyword(s):  
High Altitude ◽  
Complex Mixture ◽  
Saharan Dust ◽  
Atmospheric Composition ◽  
Urban Site ◽  
Chemical Components ◽  
Research Station ◽  
African Region ◽  
Aerosol Composition ◽  
The Impact

<p>Aerosol particles are important constituents of the atmosphere due to their role in controlling climate-related processes. In addition, their impacts on air quality and human health make it essential to study. However, the characterization and the identification of natural and anthropogenic atmospheric particles can be challenging due to the complex mixture occurring during atmospheric transport. Background locations such as high-altitude sites provide valuable infrastructure for obtaining representative data for understanding various pathways for aerosol interactions useful in assessing atmospheric composition. However, information about aerosol characteristics at high-altitude in the African regions and their relation to urban aerosol composition is still not well understood. In the present study, PM<sub>10</sub> and PM<sub>2.5</sub> particulate matter was characterized at two different sites in the North African region of Morocco. A background site located at the newly established AM5 research station in the Middle Atlas region at an altitude of 2100 m and an urban site situated in a polluted city, Fez. The goal was to determine chemical components, evaluate Saharan dust’s role on the PM10 concentrations between the sites, and assess the impact of urban pollution on background aerosol composition. The results indicate that the background aerosol composition is influenced by both regional and trans-regional transport. Despite the site's proximity to the Sahara Desert, the deserts influence on the atmospheric composition was observed for only 22% of the time and this was mainly seasonal. Marine air masses were more dominant with a mixture of sea salt and polluted aerosol from the coastal regions especially during wintertime. Furthermore, high concentrations of mineral dust were observed during the daytime due to the resuspension of road dust. At the same time, an increase of PAHs and anthropogenic metals such as Pb, Ni, and Cu were found during the nighttime because of the boundary layer variation. The Fez's urban site is characterized by a high contribution of elemental carbon (6%) and organic biomass tracers (3%) such as Levoglucosane and 4-nitrophenol.</p>

Mixing layer height and air pollution levels in urban area

2012 ◽  
Author(s):  
Klaus Schäfer ◽  
Patrick Wagner ◽  
Stefan Emeis ◽  
Carsten Jahn ◽  
Christoph Muenkel ◽  
...  
Keyword(s):  
Air Pollution ◽  
Urban Area ◽  
Mixing Layer ◽  
Layer Height ◽  
Pollution Levels ◽  
Mixing Layer Height

scholarly journals Observed and Modelled Convective Mixing-Layer Height at Dome C, Antarctica

2014 ◽  
Vol 151 (3) ◽  
pp. 597-608 ◽  
Author(s):  
Giampietro Casasanta ◽  
Ilaria Pietroni ◽  
Igor Petenko ◽  
Stefania Argentini
Keyword(s):  
Mixing Layer ◽  
Layer Height ◽  
Convective Mixing ◽  
Mixing Layer Height

scholarly journals Boundary Layer Characteristics over the Central Area of the Kathmandu Valley as Revealed by Sodar Observation

2015 ◽  
Vol 20 (1) ◽  
pp. 28-35
Author(s):  
Sajan Shrestha ◽  
Saraswati Shrestha ◽  
Sangeeta Maharjan ◽  
Ram P. Regmi
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Diurnal Variation ◽  
Mixing Layer ◽  
Central Area ◽  
Kathmandu Valley ◽  
Pollution Dispersion ◽  
Easterly Wind ◽  
Layer Height ◽  
Mixing Layer Height

The characteristic behavior of prevailing boundary layer over the central area of the Kathmandu valley was continuously monitored by deploying a monostatic flat array sodar during the period of 03 to 16 March 2013. Diurnal variation of wind and mixing layer height were chosen to describe the boundary layer activities over the area by considering the day of 12 March 2013 as the representative day for the period of observation. The study shows that central area of the valley remains calm or windless under stable stratification throughout the night and early morning frequently capped by northeasterly or easterly wind aloft. Strong surface level thermal inversion prevails during the period up to the height of 80m above the surface. This inversion tends to lift up as the morning progresses and reaches to the height of 875 m or so close to the noontime. Intrusion of regional winds as westerly/northwesterly and the southerly/southwesterly from the western and southwestern low-mountain passes and the river gorge in the afternoon tends to reduce the noontime mixing layer height to about 700 m. The diurnal variation of wind and mixing layer height suggest that Kathmandu valley possesses a poor air pollution dispersion power and hence the valley is predisposed to high air pollution potential.Journal of Institute of Science and Technology, 2015, 20(1): 28-35

scholarly journals Determination of the mixing layer height from regular lidar measurements in the Barcelona area

2004 ◽  
Author(s):  
Michael Sicard ◽  
Carlos Perez ◽  
Adolfo Comeren ◽  
Jose M. Baldasano ◽  
Francesc Rocadenbosch
Keyword(s):  
Mixing Layer ◽  
Layer Height ◽  
Lidar Measurements ◽  
Mixing Layer Height
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