Impacts of Aerosol-Radiation Interactions on the Wintertime Particulate Pollution under Different Synoptic Patterns in the Guanzhong Basin, China

Abstract

The effects of aerosol-radiation interactions (ARI) are not only important for regional and global climate, but they can also drive particulate matter (PM) pollution. In this study, the ARI contribution to the near-surface fine PM (PM_2.5) concentrations in the Guanzhong Basin (GZB) is evaluated under four unfavorable synoptic patterns, including “north-low”, “transition”, “southeast-trough”, and “inland-high”, based on WRF-Chem model simulations of a persistent heavy PM pollution episode in January 2019. Simulations show that ARI consistently decreases both solar radiation reaching down to the surface (SWDOWN) and surface temperature (TSFC), which then reduces wind speed, induces sinking motion, and influences cloud formation in the GZB. However, large differences under the four synoptic patterns still exist. The average reductions of SWDOWN and daytime TSFC in the GZB range from 15.2% and 1.04°C in the case of the “transition” pattern to 26.7% and 1.69°C in the case of the “north-low” pattern, respectively. Furthermore, ARI suppresses the development of the planetary boundary layer (PBL), with the decrease of PBL height (PBLH) varying from 18.7% in the case of the “transition” pattern to 32.0% in the case of the “north-low” pattern. The increase of daytime near-surface PM_2.5 in the GZB due to ARI is 12.0%, 8.1%, 9.5%, and 9.7% under the four synoptic patterns, respectively. Ensemble analyses also reveal that when near-surface PM_2.5 concentrations are low, ARI tends to lower PM_2.5 concentrations with decreased PBLH, which is caused by enhanced divergence or a transition from divergence to convergence in an area. ARI contributes 15%–25% toward the near-surface PM_2.5 concentrations during the severe PM pollution period under the four synoptic patterns.

摘 要

气溶胶-辐射相互作用(ARI)不仅能够影响区域和全球气候,而且是大气颗粒物污染的驱动因素。本研究基于WRF-Chem模式对2019年1月关中盆地(GZB)一次持续的颗粒物重污染事件的模拟,评估了在“北低压”、“过渡”、“东南槽”和“内陆高压”四种不利的天气形势下,ARI对关中盆地近地表细颗粒物(PM_2.5)质量浓度的贡献。模拟结果表明,ARI会持续减少到达地面的太阳辐射(SWDOWN),降低地表温度(TSFC),进一步降低近地面风速,诱发空气的下沉运动,影响云的形成。但是在四种不同的天气形势下,ARI对关中盆地内气象条件的改变和颗粒物浓度的影响存在一定的差异。模拟期间,由于ARI导致的关中盆地SWDOWN的减少从“过渡”条件下的15.2%增加到“北低压”条件下的26.7%,日间TSFC的降低从“过渡”条件下的1.04℃增加到“北低压”条件下的1.69℃。此外,ARI会抑制行星边界层(PBL)的发展,导致边界层高度(PBLH)降低,模拟期间关中盆地PBLH的下降从“过渡”条件下的18.7%增加到“北低压”条件下的32.0%。在四种天气形势下,由于ARI导致的关中盆地日间近地表PM_2.5质量浓度的平均增量分别为12.0%、8.1%、9.5%和9.7%。对近地表PM_2.5质量浓度和由ARI导致的PM_2.5的增量的集成分析发现,当近地表PM_2.5质量浓度较低时,ARI会随着PBLH的降低而降低PM_2.5浓度,这是由于区域内辐散增强或由辐散向辐合过渡所致。在四种天气形势下,ARI对近地表PM_2.5质量浓度的贡献约为15~25%。

Electronic Supplementary Material to

376_2020_329_MOESM1_ESM.pdf

Impacts of Aerosol-Radiation Interactions on the Wintertime Particulate Pollution under Different Synoptic Patterns in the Guanzhong Basin, China