青藏高原大气对流层臭氧研究进展

An overview of tropospheric ozone in the Tibetan Plateau

关键词:  青藏高原  臭氧  污染物排放  平流层入侵  影响因素

Key words:  the Tibetan Plateau  ozone  pollutants emission  stratospheric intrusion  influencing factors

摘要:

青藏高原是地球上最洁净的地区之一。然而，近年来青藏高原大气对流层臭氧（O₃ ）浓度维持在较高水平，已经形成了普遍的O₃ 污染问题。文章综述了青藏高原大气对流层O₃ 的浓度和时空分布规律， 总结了该区域O₃ 生成的主要来源及其影响因素。结果表明，青藏高原的大气对流层O₃ 浓度在全球偏远地区中属于中等偏上水平，并呈现随海拔升高而升高的趋势；此外，O₃ 日变化表现为傍晚-夜间峰值，季节变化呈现地域性差异，北部峰值出现在季风初期 （6月），中南部高值出现在季风前期 （3—5月），年际变化表现为缓慢升高。从来源上看，高原城市区域O₃ 主要受本地排放和平流层入侵的影响，偏远地区主要受平流层入侵和远距离传输的双重影响；近地表O₃ 的产生受到光照、气象条件和人为排放污染物的共同影响。在今后的研究中，需要提高偏远地区O₃ 的多维度、高分辨率监测水平，以此来更精确反演O₃ 来源和前体物质的转化关系。同时，亟待开展青藏高原对流层O₃ 的气候和环境效应研究，定量对流层O₃ 波动对青藏高原气候变化的影响，以及量化对流层O₃ 对地表植被和陆地碳氮循环的作用。

Abstract:

Background, aim, and scope The Tibetan Plateau is widely recognized for its pristine environmental conditions; nevertheless, tropospheric ozone (O₃) concentrations in this region have remained persistently elevated in recent years, raising growing concerns about widespread O₃ pollution. This review aims to systematically examine the temporal distribution of tropospheric O₃ across different geographic settings and climatic regimes within the Tibetan Plateau. Specifically, it seeks to elucidate the key drivers governing interannual, seasonal, and diurnal variations in O₃ concentrations. In addition, this review identifies existing limitations in current research and highlights critical knowledge gaps that have thus far been only sporadically addressed. By synthesizing the existing body of literature, this study endeavors to provide a comprehensive understanding of tropospheric O₃ dynamics over the plateau and to outline potential pathways for future research. Materials and methods This review is based on a comprehensive synthesis of nearly three decades of research on tropospheric ozone (O₃) over the Tibetan Plateau. In total, 26 satellite remote sensing studies, 47 chemical transport and climate model simulation studies, and 53 ground-based field observation studies published over the past about 30 years were systematically reviewed. These studies collectively provide multi-scale perspectives on the spatial and temporal variability of tropospheric O₃ across the plateau. By integrating evidence from satellite observations, numerical modeling, and in situ measurements, this review summarizes the spatiotemporal distribution characteristics of tropospheric O₃ and identifies its major sources and controlling factors, including stratospheric intrusion, long-range transport, local anthropogenic emissions, and meteorological conditions. Furthermore, based on a critical assessment of the limitations and knowledge gaps in existing studies—such as sparse observations in remote regions, uncertainties in source attribution, and insufficient quantification of transport processes—this review proposes future research strategies and directions to advance the understanding of tropospheric O₃ dynamics over the Tibetan Plateau. Results (1) Tropospheric O₃ concentrations over the Tibetan Plateau are comparable to those observed in many remote regions worldwide, with concentrations generally increasing with altitude. (2) Pronounced diurnal variations in O₃ are observed, with peak concentrations typically occurring during dusk and nighttime hours. Seasonal patterns exhibit strong spatial heterogeneity: northern regions tend to experience maximum O₃ levels during the early monsoon period (June), whereas central and southern regions reach peak concentrations during the pre-monsoon period (March—May). On interannual timescales, O₃ concentrations show a gradual increasing trend. (3) In terms of sources, tropospheric O₃ in urban areas of the plateau is influenced by a combination of local anthropogenic emissions and stratospheric intrusion, whereas O₃ in remote regions is primarily governed by stratospheric intrusion and long-range transport. Discussion The observed seasonal peaks in O₃ concentrations correspond closely with variations in the frequency and intensity of stratospheric intrusion events, underscoring the critical role of stratospheric influence in shaping seasonal O₃ variability across the Tibetan Plateau. Notably, the pre-monsoon period coincides with enhanced stratospheric intrusion activity throughout the region. Contributions from long-range transport can reach up to approximately 10 mm3 /m³ , with substantial variability depending on transport pathways, seasonal conditions, and regional topography. These differences are likely associated with source-region characteristics, meteorological conditions, and the downward transport of O₃ from the upper troposphere and lower stratosphere. Near-surface O₃ formation is governed by complex interactions among solar radiation, meteorological conditions, and anthropogenic precursor emissions. Advancing the understanding of these mechanisms requires integrated approaches, including controlled chamber experiments and precursor mixing simulations.Conclusions Although numerous studies have investigated O₃ variability and its potential sources over the Tibetan Plateau, a comprehensive quantitative assessment of the relative contributions from anthropogenic emissions, stratospheric intrusion, and long-range transport across the entire plateau remains lacking. Recommendations and perspectives Future research should prioritize the development of multidimensional, high-resolution O₃ monitoring networks in remote regions of the Tibetan Plateau to more accurately constrain O₃ sources and transformation pathways from precursor species. Concurrently, it is essential to investigate the climatic and environmental impacts of tropospheric O₃ in this region, including its influence on regional climate variability, surface vegetation dynamics, and terrestrial carbon and nitrogen cycles.