Gaoyuan qixiang (Jun 2024)

Formation and Evolution Mechanisms of A Severe Haze Event in the Sichuan Basin in Winter 2016

  • Xinbing REN,
  • Xianyu YANG,
  • Jun WEN,
  • Shigong WANG

DOI
https://doi.org/10.7522/j.issn.1000-0534.2023.00082
Journal volume & issue
Vol. 43, no. 3
pp. 775 – 789

Abstract

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Studying the formation and evolution mechanism of heavy pollution haze events is beneficial to control the regional scale air quality and to formulate the prevention policies of severe haze pollution.Based on the WRF-CMAQ model and actual observation data， a severe haze event which occurred in Chengdu of Sichuan Basin from December 23， 2016 to January 7， 2017 was reproduced.The distribution of temporal and spatial variations of PM2.5 concentration and ventilation coefficient， the physical and chemical processes and the distribution of potential pollution source areas were analyzed to study the formation and evolution mechanism of this severe pollution haze event.Major results were as follows： （1） The environmental conditions of low temperature and low wind speed during the haze event created favorable conditions for the accumulation of pollutants.（2） The northerly airflow in the north of the basin， the southwesterly airflow in the south and the lower ventilation coefficient value （weak turbulent diffusion capability of atmosphere） were the main reasons for the accumulation of pollutants.The PM2.5 concentration in Chengdu reached the peak under the influence of the northeast airflow.The dissipation of pollutants was mainly because of the strengthening of the northerly airflow and the higher ventilation coefficient value （strong turbulent diffusion capability of atmosphere）.（3） The positive contribution of the aerosol process and emission sources in this haze event was strengthened.And the increase in PM2.5 was mainly at night （the negative contribution of the advection process and the weak diffusion process） and the magnitude of the increase was greater relative to the decrease， resulting in an overall gradual increase in PM2.5.（4） PSCF and CWT analysis showed that the airflows with high PM2.5 concentration in Chengdu mainly came from its northeast and southwest directions during this haze event， and the potential pollution source areas were generally distributed in a northeast-southwest band.

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