Abstract
Abstract. During the winters (December–February) between 1985 and 2015, the North China Plain (NCP, 30–40.5∘ N, 112–121.5∘ E) suffered many periods of heavy haze, and these episodes were contemporaneous with extreme rainfall over southern China; i.e., south rainfall–north haze events. The formation of such haze events depends on meteorological conditions which are related to the atmospheric circulation associated with rainfall over southern China, but the underlying physical mechanism remains unclear. This study uses observations and model simulations to demonstrate that haze over the NCP is modulated by anomalous anticyclonic circulation caused by the two Rossby wave trains, in conjunction with the north–south circulation system, which ascends over southern China, moves north into northern China near 200–250 hPa, and then descends in the study area. Moreover, in response to rainfall heating, southern China is an obvious Rossby wave source, supporting waves along the subtropical westerly jet waveguide and finally strengthening anticyclonic circulation over the NCP. Composite analysis indicates that these changes lead to a stronger descending motion, higher relative humidity, and a weaker northerly wind, which favors the production and accumulation of haze over the NCP. A linear baroclinic model simulation reproduced the observed north–south circulation system reasonably well and supports the diagnostic analysis. Quasi-geostrophic vertical pressure velocity diagnostics were used to quantify the contributions to the north–south circulation system made by large-scale adiabatic forcing and diabatic heating (Q). The results indicated that the north–south circulation system is induced mainly by diabatic heating related to precipitation over southern China, and the effect of large-scale circulation is negligible. These results provide the basis for a more comprehensive understanding of the mechanisms that drive the formation of haze over the NCP.
Highlights
Extensive heavy haze on the North China Plain (NCP, 30– 40.5◦ N, 112–121.5◦ E) has a detrimental effect on both human health and social activities (Chen et al, 2017; Hughes et al, 2018; Lelieveld et al, 2019; Li et al, 2019)
Emissions play an important role in the generation of haze, numerous studies have suggested that meteorology is a significant factor in the occurrence of extreme haze events (Quan et al, 2011; Wang et al, 2015; Gao et al, 2016; Stirnberg et al, 2021)
Our study investigated the mechanisms associated with production over the NCP related to rainfall heating over southern China based on a combination of observational composites and model results
Summary
Extensive heavy haze on the North China Plain (NCP, 30– 40.5◦ N, 112–121.5◦ E) has a detrimental effect on both human health and social activities (Chen et al, 2017; Hughes et al, 2018; Lelieveld et al, 2019; Li et al, 2019). These haze events are caused by emissions of pollutants combined with unfavorable meteorological conditions (Yang et al, 2016; Cai et al, 2017; Ding et al, 2017; Zhang et al, 2021). There is little doubt that developing an improved understanding of the factors and mechanisms that cause haze is one of the greatest challenges facing researchers over the coming decades
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
