Measurement report: Comparison of wintertime individual particles at ground level and above the mixed layer in urban Beijing

Abstract. Beijing has been suffering from frequent severe air pollution events, with concentrations affected significantly by the mixed layer height. Major efforts have been made to study the physico-chemical properties, composition, and sources of aerosol particles at ground level. However, little is known on morphology, elemental composition, and mixing state of aerosol particles above the mixed layer. In this work, we collected individual aerosol particles simultaneously at ground level (2 m above ground) and above the mixed layer in urban Beijing (within the Atmospheric Pollution and Human Health in a Chinese Megacity (APHH-Beijing) 2016 winter campaign). The particles were analyzed off-line using transmission electron microscopy coupled with energy dispersive X-ray spectroscopy. Our results showed that the relative number contribution of mineral particles to all measured particles was much higher during non-haze periods (42.5 %) than haze periods (18.1 %); on the contrary, internally mixed particles contributed more during haze periods (21.9 %) than non-haze periods (7.2 %) at ground level. In addition, more mineral particles were found at ground level than above the mixed layer height. Around 20 % of individual particles showed core-shell structures during haze periods, whereas only a few core-shell particles were observed during non-haze periods (2 %). We found that the particle above the mixed layer tend to be more aged with a larger proportion of organic particles originated from coal combustion. Our results indicate that a significant fraction of the airborne particles above the mixed layer originated from surrounding areas influenced by coal combustion activities. This source contributes to the surface particle concentrations in Beijing when polluted air is mixed down to the ground level.

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Measurement report: Comparison of wintertime individual particles at ground level and above the mixed layer in urban Beijing

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-5301-2021 ◽

2021 ◽

Vol 21 (7) ◽

pp. 5301-5314

Author(s):

Wenhua Wang ◽

Longyi Shao ◽

Claudio Mazzoleni ◽

Yaowei Li ◽

Simone Kotthaus ◽

...

Keyword(s):

Mixed Layer ◽

Coal Combustion ◽

Large Fraction ◽

Aerosol Particles ◽

Ground Level ◽

Core Shell ◽

Layer Height ◽

Mineral Particles ◽

Mixed Layer Height ◽

Individual Particles

Abstract. Beijing has been suffering from frequent severe air pollution events, with concentrations affected significantly by the mixed-layer height. Major efforts have been made to study the physico-chemical properties, compositions, and sources of aerosol particles at ground level. However, little is known about the morphology, elemental composition, and mixing state of aerosol particles above the mixed layer. In this work, we collected individual aerosol particles simultaneously at ground level (2 m above ground) and above the mixed layer in urban Beijing (within the Atmospheric Pollution and Human Health in a Chinese Megacity, APHH-Beijing, 2016 winter campaign). The particles were analyzed offline by transmission electron microscopy coupled with energy dispersive X-ray spectroscopy. Our results showed that the relative number contribution of mineral particles to all measured particles was much higher during non-haze periods (42.5 %) than haze periods (18.1 %); in contrast, internally mixed particles contributed more during haze periods (21.9 %) than non-haze periods (7.2 %) at ground level. In addition, more mineral particles were found at ground level than above the mixed-layer height. Around 20 % of individual particles showed core–shell structures during haze periods, whereas only a few core–shell particles were observed during non-haze periods (2 %). The results showed that the particles above the mixed layer were more aged, with a larger proportion of organic particles originating from coal combustion. Our results indicate that a large fraction of the airborne particles above the mixed layer come from surrounding areas influenced by coal combustion activities. This source contributes to the surface particle concentrations in Beijing when polluted air is mixed down to the ground level.

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Assessment of mixed-layer height estimation from single-wavelength ceilometer profiles

Atmospheric Measurement Techniques ◽

10.5194/amt-10-3963-2017 ◽

2017 ◽

Vol 10 (10) ◽

pp. 3963-3983 ◽

Cited By ~ 10

Author(s):

Travis N. Knepp ◽

James J. Szykman ◽

Russell Long ◽

Rachelle M. Duvall ◽

Jonathan Krug ◽

...

Keyword(s):

Boundary Layer ◽

Data Collection ◽

Mixed Layer ◽

A Priori ◽

Processing Algorithm ◽

Height Measurement ◽

Layer Height ◽

Network Operation ◽

Mixed Layer Height ◽

The Impact

Abstract. Differing boundary/mixed-layer height measurement methods were assessed in moderately polluted and clean environments, with a focus on the Vaisala CL51 ceilometer. This intercomparison was performed as part of ongoing measurements at the Chemistry And Physics of the Atmospheric Boundary Layer Experiment (CAPABLE) site in Hampton, Virginia and during the 2014 Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field campaign that took place in and around Denver, Colorado. We analyzed CL51 data that were collected via two different methods (BLView software, which applied correction factors, and simple terminal emulation logging) to determine the impact of data collection methodology. Further, we evaluated the STRucture of the ATmosphere (STRAT) algorithm as an open-source alternative to BLView (note that the current work presents an evaluation of the BLView and STRAT algorithms and does not intend to act as a validation of either). Filtering criteria were defined according to the change in mixed-layer height (MLH) distributions for each instrument and algorithm and were applied throughout the analysis to remove high-frequency fluctuations from the MLH retrievals. Of primary interest was determining how the different data-collection methodologies and algorithms compare to each other and to radiosonde-derived boundary-layer heights when deployed as part of a larger instrument network. We determined that data-collection methodology is not as important as the processing algorithm and that much of the algorithm differences might be driven by impacts of local meteorology and precipitation events that pose algorithm difficulties. The results of this study show that a common processing algorithm is necessary for light detection and ranging (lidar)-based MLH intercomparisons and ceilometer-network operation, and that sonde-derived boundary layer heights are higher (10–15 % at midday) than lidar-derived mixed-layer heights. We show that averaging the retrieved MLH to 1 h resolution (an appropriate timescale for a priori data model initialization) significantly improved the correlation between differing instruments and differing algorithms.

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Interactive comment on “Pathfinder: Applying graph theory for consistent tracking of daytime mixed layer height with backscatter lidar” by Marco de Bruine et al.

10.5194/amt-2016-327-rc2 ◽

2016 ◽

Author(s):

Anonymous

Keyword(s):

Graph Theory ◽

Mixed Layer ◽

Layer Height ◽

Mixed Layer Height

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Use of Richardson Number Methods in Regional Models to Calculate the Mixed-Layer Height

Air Pollution Processes in Regional Scale ◽

10.1007/978-94-007-1071-9_3 ◽

2003 ◽

pp. 21-29 ◽

Cited By ~ 1

Author(s):

E. Batchvarova ◽

S.-E. Gryning

Keyword(s):

Mixed Layer ◽

Richardson Number ◽

Regional Models ◽

Layer Height ◽

Mixed Layer Height

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Atmospheric boundary layer dynamics from balloon soundings worldwide: CLASS4GL v1.0

Geoscientific Model Development ◽

10.5194/gmd-12-2139-2019 ◽

2019 ◽

Vol 12 (5) ◽

pp. 2139-2153 ◽

Cited By ~ 4

Author(s):

Hendrik Wouters ◽

Irina Y. Petrova ◽

Chiel C. van Heerwaarden ◽

Jordi Vilà-Guerau de Arellano ◽

Adriaan J. Teuling ◽

...

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Mixed Layer ◽

Weather Prediction ◽

Potential Temperature ◽

Specific Humidity ◽

Weather Extremes ◽

Coupled Models ◽

Layer Height ◽

Mixed Layer Height

Abstract. The coupling between soil, vegetation and atmosphere is thought to be crucial in the development and intensification of weather extremes, especially meteorological droughts, heat waves and severe storms. Therefore, understanding the evolution of the atmospheric boundary layer (ABL) and the role of land–atmosphere feedbacks is necessary for earlier warnings, better climate projection and timely societal adaptation. However, this understanding is hampered by the difficulties of attributing cause–effect relationships from complex coupled models and the irregular space–time distribution of in situ observations of the land–atmosphere system. As such, there is a need for simple deterministic appraisals that systematically discriminate land–atmosphere interactions from observed weather phenomena over large domains and climatological time spans. Here, we present a new interactive data platform to study the behavior of the ABL and land–atmosphere interactions based on worldwide weather balloon soundings and an ABL model. This software tool – referred to as CLASS4GL (http://class4gl.eu, last access: 27 May 2018) – is developed with the objectives of (a) mining appropriate global observational data from ∼15 million weather balloon soundings since 1981 and combining them with satellite and reanalysis data and (b) constraining and initializing a numerical model of the daytime evolution of the ABL that serves as a tool to interpret these observations mechanistically and deterministically. As a result, it fully automizes extensive global model experiments to assess the effects of land and atmospheric conditions on the ABL evolution as observed in different climate regions around the world. The suitability of the set of observations, model formulations and global parameters employed by CLASS4GL is extensively validated. In most cases, the framework is able to realistically reproduce the observed daytime response of the mixed-layer height, potential temperature and specific humidity from the balloon soundings. In this extensive global validation exercise, a bias of 10.1 m h−1, −0.036 K h−1 and 0.06 g kg−1 h−1 is found for the morning-to-afternoon evolution of the mixed-layer height, potential temperature and specific humidity. The virtual tool is in continuous development and aims to foster a better process understanding of the drivers of the ABL evolution and their global distribution, particularly during the onset and amplification of weather extremes. Finally, it can also be used to scrutinize the representation of land–atmosphere feedbacks and ABL dynamics in Earth system models, numerical weather prediction models, atmospheric reanalysis and satellite retrievals, with the ultimate goal of improving local climate projections, providing earlier warning of extreme weather and fostering a more effective development of climate adaptation strategies. The tool can be easily downloaded via http://class4gl.eu (last access: 27 May 2018) and is open source.

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