Study on aerosols and BC cross-layer transport at the top of the planetary boundary layer based on aircraft observations in autumn over the North China Plain

IF 4.2 2区环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES

Atmospheric Environment Pub Date : 2025-04-16 DOI:10.1016/j.atmosenv.2025.121244

Kun Cui , Sihan Liu , Honglei Wang , Yang Yang , Yi Cui , Zihan Wang , Fan Zu , Lijuan Shen , Yue Ke , Zihao Wu , Tianliang Zhao

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Abstract

Vertical profiles of aerosol and black carbon (BC) play a critical role in the evolution process of the planetary boundary layer (PBL) structure, and pollutant transport. Eleven aircraft observations of aerosols and BC were launched in the North China Plain (NCP) in the autumn of 2019 and 2020. The aerosol number concentration (Na) and BC concentration (M_BC) below 2000 m in NCP have obvious diurnal variation characteristics. From 11:00 to 16:00, Na exhibited double peaks, with one peak identified near the top of PBL (8380.57 cm⁻³) and the second peak occurring near-surface (9692.13 cm⁻³), a downward Na gradient exists below the top of the planetary boundary layer height (PBLH) (850m–1400m) and increases with time (3.93 cm⁻³/m to 9.64 cm⁻³/m). During 17:00–21:00, Na and M_BC exhibited a peak concentrated near the surface (the maximum values were 10077.74 cm⁻³ and 14.03 μg m⁻³), an upward Na gradient (17.73 cm⁻³/m) is present at the top of PBLH (100 m–280 m) well above the daytime level. The aerosol spectral distribution was bimodal with predominant particle diameters at 0.14 μm and 0.20 μm, and aerosols of 0.14 μm showed stronger vertical dispersion from 19:00 to 21:00. Aerosol and BC transport between the PBL and the free troposphere (FT) was bidirectional. Transport from the FT to PBL from 11:00 to 16:00, transport from PBL to FT from 17:00 to 21:00. 11:00 to 14:00, as the PBLH rose (1000m–1400m), aerosols and BC were transported to 1000–1500 m and accumulated within the PBL. 14:00 to 16:00, the combination of, the inversion layer and the downdraft air over the PBL resulted in a peak Na in the top of PBL from 14:00 to 16:00, Na gradient from the FT to PBL expands between 11:00 and 16:00. From 19:00 to 21:00, the height of the PBL was the lowest (300m–100m). Due to the decrease of PBLH, aerosol and BC were confined within the near-surface, leading to a significant increase in near-surface Na and M_BC, which were elevated by factors of 1.82 and 4.04, compared to their levels during 11:00–14:00, upward Na gradient from the top of PBLH increased at night, allowed for upward aerosol transport at night. The direction of air mass origins affects aerosol and BC behavior at different altitudes.

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基于飞机观测的华北平原秋季行星边界层顶部气溶胶和BC跨层输送研究

气溶胶和黑碳（BC）的垂直剖面在行星边界层（PBL）结构的演化过程和污染物的运移中起着至关重要的作用。2019年秋季和2020年秋季在华北平原开展了11次气溶胶和BC的飞机观测。2000 m以下气溶胶数浓度（Na）和BC浓度（MBC）具有明显的日变化特征。11:00 ~ 16:00， Na呈双峰分布，其中一个峰出现在边界层顶部（8380.57 cm−3），另一个峰出现在近地表（9692.13 cm−3），在行星边界层高度（PBLH）顶部（850m ~ 1400m）以下存在一个向下的Na梯度，并随时间增加（3.93 cm−3/m ~ 9.64 cm−3/m）。在17:00-21:00期间，Na和MBC在地表附近出现峰值（最大值分别为10077.74 cm−3和14.03 μ m−3），在PBLH顶部（100 ~ 280 m）， Na梯度呈上升趋势（17.73 cm−3/m），远高于白天水平。气溶胶光谱分布呈双峰型，主要粒径为0.14 μm和0.20 μm，且0.14 μm的气溶胶在19:00 ~ 21:00表现出较强的垂直色散。气溶胶和BC在PBL和自由对流层（FT）之间的输送是双向的。11:00 - 16:00从FT到PBL， 17:00 - 21:00从PBL到FT。11:00 ~ 14:00，随着PBLH的上升（1000 ~ 1400m），气溶胶和BC被输送到1000 ~ 1500 m并在PBL内积累。14:00 ~ 16:00，逆温层与PBL上方的下沉气流共同作用，导致PBL顶部在14:00 ~ 16:00出现Na峰值，从FT到PBL的Na梯度在11:00 ~ 16:00之间扩大。19:00 ~ 21:00，边界层高度最低（300 ~ 100m）。由于PBLH的减少，气溶胶和BC被限制在近地表，导致近地表Na和MBC显著增加，与11:00-14:00相比，Na和MBC分别升高了1.82和4.04倍，夜间PBLH顶部向上的Na梯度增加，有利于夜间气溶胶向上输送。气团起源的方向在不同高度影响气溶胶和BC的行为。

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来源期刊

Atmospheric Environment 环境科学-环境科学

CiteScore

9.40

自引率

8.00%

发文量

458

审稿时长

53 days

期刊介绍： Atmospheric Environment has an open access mirror journal Atmospheric Environment: X, sharing the same aims and scope, editorial team, submission system and rigorous peer review. Atmospheric Environment is the international journal for scientists in different disciplines related to atmospheric composition and its impacts. The journal publishes scientific articles with atmospheric relevance of emissions and depositions of gaseous and particulate compounds, chemical processes and physical effects in the atmosphere, as well as impacts of the changing atmospheric composition on human health, air quality, climate change, and ecosystems.