气候变化领域集成服务门户(CCPortal): The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms

CCPortal

DOI	10.5194/acp-22-15243-2022
	The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms
	He, Cheng; Lu, Xiao; Wang, Haolin; Wang, Haichao; Li, Yan; He, Guowen; He, Yuanping; Wang, Yurun; Zhang, Youlang; Liu, Yiming; Fan, Qi; Fan, Shaojia
发表日期	2022
ISSN	1680-7316
EISSN	1680-7324
起始页码	15243
结束页码	15261
卷号	22 期号:23 页码:19
英文摘要	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.
学科领域	Environmental Sciences; Meteorology & Atmospheric Sciences
语种	英语
WOS研究方向	Environmental Sciences & Ecology ; Meteorology & Atmospheric Sciences
WOS记录号	WOS:000892562800001
来源期刊	ATMOSPHERIC CHEMISTRY AND PHYSICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/273169
作者单位	Sun Yat Sen University; Southern Marine Science & Engineering Guangdong Laboratory; Southern Marine Science & Engineering Guangdong Laboratory (Zhuhai); China West Normal University; University of California System; University of California Davis
推荐引用方式 GB/T 7714	He, Cheng,Lu, Xiao,Wang, Haolin,et al. The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms[J],2022,22(23):19.
APA	He, Cheng.,Lu, Xiao.,Wang, Haolin.,Wang, Haichao.,Li, Yan.,...&Fan, Shaojia.(2022).The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms.ATMOSPHERIC CHEMISTRY AND PHYSICS,22(23),19.
MLA	He, Cheng,et al."The unexpected high frequency of nocturnal surface ozone enhancement events over China: characteristics and mechanisms".ATMOSPHERIC CHEMISTRY AND PHYSICS 22.23(2022):19.