Intermittent turbulence contributes to vertical diffusion of PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; in
the North China Plain

Wei, Wei; Zhang, Hongsheng; Wu, Bingui; Huang, Yongxiang; Cai, Xiaoling; Song, Yu; Li, Jianduo

doi:10.5194/acp-2018-121

Cited by 4 publications

(5 citation statements)

References 38 publications

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“…The increase in concentration with height is potentially linked to the regional transport and gas-to-particle processes of semi-volatile VOCs due to lower temperatures at the upper layers (Goldstein et al, 2009). Moreover, vertical convection transport and BVOCs emission sources cannot be ignored (Ran et al, 2012;Wei et al, 2018b).…”

Section: Vertical Distribution Of Bsoa Tracersmentioning

confidence: 99%

Comment on acp-2021-136

2021

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Secondary organic aerosols (SOA) play a significant role in atmospheric chemistry. However, little is known about the vertical profiles of SOA in the urban boundary layer (UBL). This gap in the knowledge constrains the SOA simulation in chemical transport models. Here, we synchronously collected aerosol samples at 8 m, 120 m and 260 m based on a 325-m meteorological tower in urban Beijing from August 15 th to September 10 th , 2015. Strict emission controls were implemented during this period for the 2015 China Victory Day Parade. The sum of biogenic SOA tracers increased withheight. The fraction of SOA from isoprene oxidation increased, whereas the fraction of monoterpene and sesquiterpene SOA decreased with height. The 2,3-dihydroxy-4-oxopentanoic acid (DHOPA), one tracer of anthropogenic SOA from toluene oxidation, also increased with height. The complicated vertical profiles of SOA tracers highlighted the needs to measure SOA within the UBL. The sum of estimated secondary organic carbon (SOC) ranged from 341 to 673 ngC m -3 . The increase in the SOC fraction from isoprene and toluene with height was found to be more related to regional transport whereas the decrease in the SOC from monoterpene and sesquiterpene with height was more subject to local emissions. Emission controls during the parade reduced SOC by 4-35% with toluene SOC decreasing more than the other SOC. This study demonstrates that vertical distributions of SOA within the UBL are complex, and the vertical profiles of SOA concentrations and sources should be considered in the future field and modelling studies.

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Section: Vertical Distribution Of Bsoa Tracersmentioning

confidence: 99%

Comment on acp-2021-136

2021

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“…Figure 8 shows the results of the same variables at the city site. Wei et al (2018) has shown that there is a relationship between the IF, which characterizes the intensity of 10 intermittent mixing, and the concentration of PM2.5. In this section, we also present the IF of the vertical wind speed in Fig.…”

Section: The Relationship Between the Local Intermittent Strength Andmentioning

confidence: 99%

“…We also note the relationship between the LIST and IF. Wei et al (2018) mentioned that the larger the absolute value of the IF is, the stronger the intermittent mixing. From the perspective of intermittent mixing strength, the IF tends to be consistent with the LIST defined in this paper.…”

Section: The Relationship Between the Local Intermittent Strength Andmentioning

confidence: 99%

“…During pollution periods, previous studies have indicated that meteorological conditions always include constant stagnant winds, relatively increased water-vapor density, and strong stable stratification, which inhibits the diffusion of vertical pollution and results in the explosive growth of PM2.5 in Beijing Wei et al 2018;Zhong et al 2018). The 5 diurnal variations in particulate concentrations are mostly dominated by the diurnal variability of the boundary layer and source emissions ; Turbulent motion determines the meteorological elements in the atmospheric boundary layer, such as turbulence diffusion, PBL height and atmospheric circulation patterns, are all key to hazy weather Tang et al, 2016;Zhu et al, 2018;) and dominate whether the haze occurs or not, since emissions can remain stable within a defined period in a certain area.…”

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confidence: 99%

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Effects of turbulence structure and urbanization on the heavy haze pollution process

Ren¹,

Zhang²,

Wei³

et al. 2018

Preprint

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In this paper, an automated algorithm, which is used to identify the spectral gap during the heavy haze pollution process, reconstruct acquired data, and obtain pure turbulence data, is developed. Comparisons of the reconstructed turbulent flux and eddy covariance (EC) flux show that there are overestimations regarding the exchange between the surface and the atmosphere during heavy haze pollution episodes. After reconstruction via the automated algorithm, pure turbulence data can be obtained. We introduce a definition to characterize the local intermittent strength of turbulence (LIST). The trend in the 15 LIST during pollution episodes shows that when pollution is more intense, the LIST is smaller, and intermittency is stronger; when pollution is weaker, the LIST is larger, and intermittency is weaker. During the heavy pollution process, air quality on an hourly scale is determined via turbulent motion. At the same time, the LIST at the city site is greater than that at the suburban site, which means that intermittency over the complex city area is weaker than that over the flat terrain area.Urbanization seems to reduce intermittency during heavy haze pollution episodes, which means that urbanization reduces the 20 degree of weakening in turbulent exchange during pollution episodes. This result is confirmed by comparing the average diurnal variations in turbulent fluxes at urban and suburban sites during polluted and clean periods. The sensible heat flux, latent heat flux, momentum flux, and turbulent kinetic energy (TKE) in urban and suburban areas are all affected when pollution occurs. Material and energy exchanges between the surface and the atmosphere are inhibited. Moreover, the impact of the pollution process on suburban areas is much greater than that on urban areas. Urbanization seems to help reduce the 25 consequences of pollution.

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“…The LLJ is a key component of the Earth's climate as it can favour the development of deep moist convection by transporting warm and moist air and promoting ascent in the jet exit region (e.g., Means, 1954;Stensrud, 1996;Gimeno et al, 2016;Algarra et al, 2019;Braz et al, 2021). LLJs are also important due to their effect on aerosols dispersion (Wei et al, 2018;Ulke et al, 2014), birds' migration (Wainwright et al, 2016), aviation safety (Arkell, 2000;Madougou et al, 2014), and wind energy (Gutierrez et al, 2014;Gadde and Stevens, 2021). Stensrud (1996), Paegle (1998), Shapiro et al (2016), and Braz et al (2021) reviewed and synthesized more than six decades of LLJ studies worldwide.…”

Section: Introductionmentioning

confidence: 99%

Observational study of the South American low‐level jet during the SALLJEX

Sol

Nicolini

Borque

et al. 2022

Intl Journal of Climatology

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The South American low-level jet (SALLJ) is a narrow northerly wind speed maximum present just above the boundary layer. It is an important component of the tropical-extratropical heat and moisture exchange in South America and can favour deep moist convection in southeastern South America. The main objective of this study is to analyse the SALLJ characteristics at 21 upper-air stations deployed between the Tropics and the subtropics from just east of the Andes to the eastern plains during the SALLJ Experiment (SALLJEX). The greatest wind speed occurs between 300 and 2,000 m AGL between 0300 and 1200 UTC, mainly in connection with greater northerly winds during an anticlockwise rotation of the wind from sunset to sunrise, thus suggesting the important role of the inertial oscillation in the wind's diurnal cycle. The spatial variation of the LLJ throughout the SALLJEX network shows a weakening of the maximum wind speed from stations near the Andes towards the Plains suggesting the presence of the LLJ core just east of the Andes around Santa Cruz de la Sierra's latitude (17 48 0 S). Weak, moderate, and strong SALLJ categories defined from a local maximum northerly wind speed threshold at each station are defined to analyse the relationship between the SALLJ intensity and the thermodynamic properties of the lower layers of the atmosphere. Strong SALLJs are frequently observed at night-time, while weak SALLJs are likely to occur at any time of the day. Strong cases have deeper and less stable nocturnal boundary layers, which could be due to the SALLJ warm advection near the time of wind speed maximum (0600 UTC). Deeper convective boundary layers and higher low-level temperatures observed at 1800 UTC prior to strong nocturnal SALLJs can potentially lead to larger amplitudes of inertial oscillation and contribute to generating stronger SALLJs.

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Intermittent turbulence contributes to vertical diffusion of PM<sub>2.5</sub> in the North China Plain

Cited by 4 publications

References 38 publications

Comment on acp-2021-136

Comment on acp-2021-136

Effects of turbulence structure and urbanization on the heavy haze pollution process

Observational study of the South American low‐level jet during the SALLJEX

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Intermittent turbulence contributes to vertical diffusion of PM&lt;sub&gt;2.5&lt;/sub&gt; in the North China Plain

Cited by 4 publications

References 38 publications

Comment on acp-2021-136

Comment on acp-2021-136

Effects of turbulence structure and urbanization on the heavy haze pollution process

Observational study of the South American low‐level jet during the SALLJEX

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Product

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Intermittent turbulence contributes to vertical diffusion of PM<sub>2.5</sub> in the North China Plain