Origin of springtime ozone enhancements in the lower troposphere over Beijing: in situ measurements and model analysis

Abstract

Abstract. Ozone (O 3 ) concentrations in the lower troposphere (LT) over Beijing have significantly increased over the past 2 decades as a result of rapid industrialization in China, with important implications for regional air quality and the photochemistry of the background troposphere. We characterize the vertical distribution of lower-tropospheric (0-6 km) O 3 over Beijing using observations from 16 ozonesonde soundings during a field campaign in April-May 2005 and MOZAIC (Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft) over 13 days in the same period. We focus on the origin of LT O 3 enhancements observed over Beijing, particularly in May. We use a global 3-D chemistry and transport model (GEOS-Chem CTM; GEOS -Goddard Earth Observing System) driven by assimilated meteorological fields to examine the transport pathways for O 3 pollution and to quantify the sources contributing to O 3 and its enhancements in the springtime LT over Beijing. Output from the Global Modeling Initiative (GMI) CTM is also used. High O 3 concentrations (up to 94.7 ppbv) were frequently observed at the altitude of ∼ 1.5-2 km. The CTMs captured the timing of the occurrences but significantly underestimated their magnitude. GEOS-Chem simulations and a case study showed that O 3 produced in the Asian troposphere (especially from Asian anthropogenic pollution) made major contributions to the observed O 3 enhancements. Contributions from anthropogenic pollution in the European and North American troposphere were reduced during these events, in contrast with days without O 3 enhancements when contributions from Europe and North America were substantial. The O 3 enhancements typically occurred under southerly wind and warmer conditions. It is suggested that an earlier onset of the Asian summer monsoon would cause more O 3 enhancement events in the LT over the North China Plain in late spring and early summer.Published by Copernicus Publications on behalf of the European Geosciences Union.

Springtime daily variations in lower-tropospheric ozone over east Asia: the role of cyclonic activity and pollution as observed from space with IASI

“…5 and 15 May 2008). This is in agreement with in situ measurements (Huang et al, 2015), considering the limited vertical resolution of IASI and its limited sensitivity to surface ozone. Because of these limitations, it is not possible to determine more precisely the altitude of the ozone enhancements in the troposphere.…”

“…The maximal values of ozone are retrieved between 2 and 3 km over Beijing (Fig. 3) in agreement, considering the vertical sensitivity and resolution of IASI, with in situ measurements, which frequently report high ozone concentrations at an altitude of 1.5-2 km above Beijing during April-May (Huang et al, 2015). This associated with the correlation with CO suggests that the enhanced ozone observed with IASI is mainly due to the photochemical transformation of primary pollutants emitted over the NCP.…”

Local and synoptic meteorological influences on daily variability in summertime surface ozone in eastern China

“…Weather classification is a well-established tool for characterizing atmospheric processes on multiple scales and further for studying the air-pollution-weather relationship (Han et al, 2018b). The methods for weather classification can be generally categorized into three groups: subjective, mixed, and objective, depending on the automatic degree during the classification process (Huth et al, 2008). The methods can also be categorized in more detail according to the basic features of each classification algorithm (Philipp et al, 2014).…”

Detection of deep stratospheric intrusions by cosmogenic 35 S

“…It also controls the lifetime of other reactive greenhouse gases through oxidation processes (3), serves as the dominant precursor of the hydroxyl radical, and enhances the oxidizing capacity of the troposphere (4). Tropospheric O 3 formation involves a series of photochemical reactions related to anthropogenic emissions of O 3 precursors [e.g., nitrogen oxides (NO x ), carbon monoxide (CO), and volatile organic compounds (VOCs)], biomass burning, and lightning (5). In addition, elevated levels of tropospheric O 3 may be caused by the intrusion of O 3 -rich stratospheric air masses (4,(6)(7)(8).…”