Preprints
https://doi.org/10.5194/acp-2021-402
https://doi.org/10.5194/acp-2021-402

  22 Jun 2021

22 Jun 2021

Review status: this preprint is currently under review for the journal ACP.

Effect of rainfall-induced diabatic heating over southern China on the formation of wintertime haze on the North China Plain

Xiadong An1, Lifang Sheng1,2,3, Chun Li1,3, Wen Chen4, Yulian Tang4, and Jingliang Huangfu4 Xiadong An et al.
  • 1Department of Marine Meteorology, College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao 266100, China
  • 2Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province, Haikou 570000, China
  • 3Ocean-Atmosphere Interaction and Climate Laboratory, Key Laboratory of Physical Oceanography, Ocean University of China, Qingdao 266100, China
  • 4Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100190, China

Abstract. During the winters (December–February) between 1985 and 2015, the North China Plain (NCP) 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 controlled by 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 Rossby wave train, in conjunction with the north−south circulation system (NSC), 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 (LBM) simulation reproduced the observed NSC reasonably well and supports the diagnostic analysis. Quasi-geostrophic (QG) vertical pressure velocity (ω) diagnostics were used to quantify the contributions to the NSC made by large-scale adiabatic forcing and diabatic heating. The results indicated that the NSC 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.

Xiadong An et al.

Status: open (until 03 Aug 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-402', Anonymous Referee #1, 09 Jul 2021 reply
  • RC2: 'Comment on acp-2021-402', Anonymous Referee #2, 18 Jul 2021 reply

Xiadong An et al.

Xiadong An et al.

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Short summary
The North China Plain (NCP) suffered many periods of haze in winter during 1985–2015, which is related to the rainfall-induced diabatic heating over southern China. The haze over the NCP is modulated by anomalous anticyclone caused by the Rossby wave and a north–south circulation (NSC) induced mainly by diabatic heating. As a Rossby wave source, the rainfall-induced diabatic supports waves and finally strengthening anticyclone over the NCP. These changes favor haze over the NCP.
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