Nocturnal surface ozone enhancement over Portugal during winter: Influence of different atmospheric conditions

Kulkarni, Pavan S.; Dasari, Hari Prasad; Sharma, Ashish; Bortoli, Daniele; Salgado, Rui; Silva, Ana Maria

doi:10.1016/j.atmosenv.2016.09.056

Cited by 14 publications

(4 citation statements)

References 42 publications

(55 reference statements)

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“…Thus, this case presents how the development of boundary layer low-level jets triggers NOE events. The lowlevel jets have also been identified as a key factor causing multiple NOE events in different regions in China Wu et al, 2022), the US (Kuang et al, 2011;Hu et al, 2013;Sullivan et al, 2017;Caputi et al, 2019), and Europe (Kulkarni et al, 2016;Klein et al, 2019). tion, lifting the surface ozone level from 9 to 34 ppbv.…”

Section: Case Studies Of Noe Eventsmentioning

confidence: 99%

“…A number of studies have reported episodic nocturnal ozone enhancement events at individual sites around the world (Eliasson et al, 2003;Hu et al, 2012Hu et al, , 2013Klein et al, 2014;Kulkarni et al, 2016;Caputi et al, 2019;He et al, 2021). The reported nocturnal ozone enhancements mostly ranged from 5 to 30 ppbv, but they were found to be up to 70 ppbv in an extreme event observed in summer 2013 over the North China Plain (Jia et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

Wang

et al. 2022

Atmos. Chem. Phys.

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Abstract. Surface ozone concentrations typically peak during the daytime, driven by active photochemical production, and decrease gradually after sunset, due to chemical destruction and dry deposition. Here, we report that nocturnal ozone enhancement (NOE, defined as an ozone increase of more than 5 ppbv h−1 in 1 of any 2 adjacent hours between 20:00 and 06:00 LT, local time) events are observed at multiple monitoring sites in China at a high frequency, which has not been recognized in previous studies. We present an overview of the general characteristics of NOE events in China and explore the possible mechanisms based on 6 years of observations from the national monitoring network. We find that the mean annual frequency of NOE events is 41±10 % (i.e., about 140 d would experience an NOE event per year) averaged over all 814 Chinese sites between 2014 and 2019, which is 46 % larger than that over Europe or the United States. The NOE event frequency is higher in industrialized city clusters (>50 %) than in regions with lighter ozone pollution, and it is higher in the warm season (46 %) than in the cold season (36 %), consistent with the spatiotemporal evolution of ozone levels. The mean ozone peak during NOE events reaches 37±6 ppbv in the warm season. The ozone enhancements are within 5–15 ppbv h−1 during 85 % of the NOE events; however, in about 10 % of cases, the ozone increases can exceed 20 ppbv h−1. We propose that high photochemistry-induced ozone during the daytime provides a rich ozone source in the nighttime residual layer, determining the overall high frequency of NOE events in China, and that enhanced atmospheric mixing then triggers NOE events by allowing the ozone-rich air in the residual layer to mix into the nighttime boundary layer. This is supported by our analyses which show that 70 % (65 %) of the NOE events are associated with increases in friction velocity (planetary boundary layer height), indicative of enhanced atmospheric mixing, and also supported by the observed sharp decreases in surface NO2 and CO concentrations with ozone increases in NOE events, a typical signal of mixing with air in the residual layer. Three case studies in Beijing and Guangzhou show that synoptic processes such as convective storms and low-level jets can lead to NOE events by aggravating vertical mixing. Horizontal transport of ozone-rich plumes may also be a supplementary driver of NOE events. Our results summarize, for the first time, the characteristics and mechanism of NOE events in China based on nationwide and long-term observations, and our findings emphasize the need for more direct measurements and modeling studies on the nighttime ozone evolution from the surface to the residual layer.

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Section: Case Studies Of Noe Eventsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

Wang

et al. 2022

Atmos. Chem. Phys.

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“…In their review article, Wei et al (2023) suggest that LLJs are a common feature and they discuss the implications this may have on the dispersion of gases and particulates. Wei et al (2023) indicate that LLJs have at least two effects on air concentrations: (a) decreases due to long‐range advection of pollutants above the LLJ (Banta et al, 1998; Corsmeier et al, 1997; Klein et al, 2019; Martins et al, 2018) and (b) increases below the LLJ due to downward momentum brought about by the enhanced vertical wind shear (Fiedler et al, 2013; Karipot et al, 2006; Kulkarni et al, 2016; Schepanski et al, 2009). Our results are consistent with the first of these effects.…”

Section: Resultsmentioning

confidence: 99%

A case study analysis of the impact of a new free tropospheric turbulence scheme on the dispersion of an atmospheric tracer

Mirza,

Dacre,

2024

Quart J Royal Meteoro Soc

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Most Lagrangian dispersion models represent free tropospheric turbulence as a homogeneous steady‐state process. However, intermittent turbulent mixing in the free troposphere may be a significant source of mixing. We test a new parametrization scheme that represents spatial‐ and temporal‐varying turbulence in the free troposphere in the Met Office's Numerical Atmospheric‐dispersion Modelling Environment. We use semi‐idealized emissions of radon‐222 (Rn) from rocks and soil in the United Kingdom to evaluate the impact of using a variable free tropospheric turbulence parameterization on the dispersion of Rn. We performed two experiments, the first using the existing steady‐state scheme and the second using the newly implemented spatio‐temporal‐varying scheme, for two case periods July 2018 and April 2021. We find that the turbulence in the varying scheme (represented by the vertical velocity variance) can range by two to three orders of magnitude (10 to 10 m s) when compared with the steady‐state scheme (10 m s). In particular, low‐altitude turbulence is enhanced when synoptic conditions are conducive to forming low‐level jets. This leads to a greater dispersion in the free troposphere, reducing the mean monthly Rn concentration above the boundary layer by 20–40% relative to the steady‐state scheme. We conclude that without a space–time‐varying free tropospheric turbulence scheme atmospheric dispersion may be significantly underestimated under synoptic conditions that are favourable for low‐level jet formation. This underestimation of dispersion may potentially result in inaccurate estimations of local emissions in top‐down greenhouse gas inventory studies.

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“…This event results from the horizontal and vertical transport of ozone and its precursors [13]. Studies of nocturnal ozone concentration increase were developed in the Portuguese continent to explain unexpected ozone levels [21,36]. The ozone enhancement events can be related to transport processes and the related usual meteorological conditions due to the absence of photochemical production.…”

Section: Surface Ozone At Rural Stationsmentioning

confidence: 99%

Surface Ozone Pollution: Trends, Meteorological Influences, and Chemical Precursors in Portugal

Silva

Pires

2022

Sustainability

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Surface ozone (O3) is a secondary air pollutant, harmful to human health and vegetation. To provide a long-term study of O3 concentrations in Portugal (study period: 2009–2019), a statistical analysis of ozone trends in rural stations (where the highest concentrations can be found) was first performed. Additionally, the effect of nitrogen oxides (NOx) and meteorological variables on O3 concentrations were evaluated in different environments in northern Portugal. A decreasing trend of O3 concentrations was observed in almost all monitoring stations. However, several exceedances to the standard values legislated for human health and vegetation protection were recorded. Daily and seasonal O3 profiles showed high concentrations in the afternoon and summer (for all inland rural stations) or spring (for Portuguese islands). The high number of groups obtained from the cluster analysis showed the difference of ozone behaviour amongst the existent rural stations, highlighting the effectiveness of the current geographical distribution of monitoring stations. Stronger correlations between O3, NO, and NO2 were detected at the urban site, indicating that the O3 concentration was more NOx-sensitive in urban environments. Solar radiation showed a higher correlation with O3 concentration regarding the meteorological influence. The wind and pollutants transport must also be considered in air quality studies. The presented results enable the definition of air quality policies to prevent and/or mitigate unfavourable outcomes from O3 pollution.

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Nocturnal surface ozone enhancement over Portugal during winter: Influence of different atmospheric conditions

Cited by 14 publications

References 42 publications

The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

A case study analysis of the impact of a new free tropospheric turbulence scheme on the dispersion of an atmospheric tracer

Surface Ozone Pollution: Trends, Meteorological Influences, and Chemical Precursors in Portugal

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