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The impacts of the atmospheric boundary layer on regional haze in North China
npj Climate and Atmospheric Science ( IF 8.5 ) Pub Date : 2021-02-22 , DOI: 10.1038/s41612-021-00165-y
Qianhui Li , Hongsheng Zhang , Xuhui Cai , Yu Song , Tong Zhu

An intensive atmospheric boundary layer (ABL) experiment was conducted simultaneously at six stations arranged in a cross shape on the North China Plain (NCP) from 26 November to 26 December 2019. The impacts of the regional ABL structure on heavy haze pollution and the relationship between the ABL height and aerosol accumulation layer (AAL) depth were discussed. Bouts of downdrafts generate a persistent descending elevated inversion layer, helping the maintenance and exacerbation of haze pollution. Continuous weak wind layers contribute to the pollutants accumulation, and low-level jets promote the removal of air pollutants. The unique landform conditions of the NCP are reflected in its regional ABL structure and further affect the spatial distribution of haze pollution. Due to the drainage flow and strong downdrafts, the western stations near the mountains have a colder surface and warmer upper air masses, resulting in a more stable stratification and worse diffusion conditions; these stations also experience a thicker weak wind layer caused by increased friction. Thus, the spatial distribution of haze is heavier in the west and lighter in the east. The convective boundary layer (CBL) height declines evidently during haze episodes, usually lower than 560 m. Furthermore, as the vertical distribution of aerosols is mainly influenced by daytime thermal turbulence and maintained at night, it is appropriate to determine the CBL height using the AAL depth. However, the AAL depth is not consistent with the stable boundary layer height due to the influence of the residual layer at night.



中文翻译:

大气边界层对华北区域霾的影响

2019年11月26日至12月26日在华北平原(NCP)上以十字形排列的六个站点同时进行了密集的大气边界层(ABL)实验。区域ABL结构对重度雾霾污染的影响及其关系讨论了ABL高度与气溶胶堆积层(AAL)深度之间的关系。下沉的气流会产生持续下降的反演层,有助于维持和加剧雾霾污染。持续的弱风层促进了污染物的积累,低空急流促进了空气污染物的清除。NCP独特的地形条件反映在其区域ABL结构中,并进一步影响了霾污染的空间分布。由于排水流和强烈的向下气流,山区附近的西部站点地表较冷,高层空气质量较暖,导致分层更加稳定,扩散条件更差;这些站点还由于摩擦增加而遇到较厚的弱风层。因此,霾的空间分布在西部较重,在东部较轻。对流边界层(CBL)的高度在霾天气期间明显下降,通常低于560 m。此外,由于气溶胶的垂直分布主要受白天热湍流的影响,并在夜间保持,因此使用AAL深度确定CBL高度是适当的。然而,由于夜间残留层的影响,AAL深度与稳定边界层高度不一致。导致更稳定的分层和更差的扩散条件;这些站点还由于摩擦增加而遇到较厚的弱风层。因此,霾的空间分布在西部较重,在东部较轻。对流边界层(CBL)的高度在霾天气期间明显下降,通常低于560 m。此外,由于气溶胶的垂直分布主要受白天热湍流的影响,并在夜间保持,因此使用AAL深度确定CBL高度是适当的。然而,由于夜间残留层的影响,AAL深度与稳定边界层高度不一致。导致更稳定的分层和更差的扩散条件;这些站点还由于摩擦增加而遇到较厚的弱风层。因此,霾的空间分布在西部较重,在东部较轻。对流边界层(CBL)的高度在霾天气期间明显下降,通常低于560 m。此外,由于气溶胶的垂直分布主要受白天热湍流的影响,并在夜间保持,因此使用AAL深度确定CBL高度是适当的。然而,由于夜间残留层的影响,AAL深度与稳定边界层高度不一致。霾的空间分布在西部较重,在东部较轻。对流边界层(CBL)的高度在霾天气期间明显下降,通常低于560 m。此外,由于气溶胶的垂直分布主要受白天热湍流的影响,并在夜间保持,因此使用AAL深度确定CBL高度是适当的。然而,由于夜间残留层的影响,AAL深度与稳定边界层高度不一致。霾的空间分布在西部较重,在东部较轻。对流边界层(CBL)的高度在霾天气期间明显下降,通常低于560 m。此外,由于气溶胶的垂直分布主要受白天热湍流的影响,并在夜间保持,因此使用AAL深度确定CBL高度是适当的。然而,由于夜间残留层的影响,AAL深度与稳定边界层高度不一致。使用AAL深度确定CBL高度是适当的。然而,由于夜间残留层的影响,AAL深度与稳定边界层高度不一致。使用AAL深度确定CBL高度是适当的。然而,由于夜间残留层的影响,AAL深度与稳定边界层高度不一致。

更新日期:2021-02-23
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