Global modeling studies of composition and decadal trends of the Asian Tropopause Aerosol Layer
Global modeling studies of composition and decadal trends of the Asian Tropopause Aerosol Layer
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DOI：
10.5194/acp-21-2745-2021
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发表时间：
2021-02
影响因子：
6.3
通讯作者：
Adriana Bossolasco;F. Jégou;P. Sellitto;G. Berthet;C. Kloss;B. Legras
中科院分区：
文献类型：
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作者：
Adriana Bossolasco;F. Jégou;P. Sellitto;G. Berthet;C. Kloss;B. Legras
抽象。亚洲夏季风（ASM）将对流抬升的边界层污染物截留在对流层上部和平流层下部的亚洲季风反气旋（AMA）中。它与一个季节性和空间局限的增强气溶胶层，称为亚洲对流层顶气溶胶层（ATL）。由于AMA的动态变化，缺乏在这一地区的原位观测，排放源和传输路径的复杂性，知识的ATAL属性的气溶胶预算，化学成分，以及它的变化和时间趋势在很大程度上仍然是不确定的。在这项工作中，我们使用社区地球系统模式（CESM1.2版本）的基础上耦合的社区大气模式（CAM 5）和MAM 7（模态气溶胶模式）气溶胶模块模拟的组成ATAL及其年代际趋势。我们的模拟涵盖了从2000年到2015年的16年。我们确定了一个典型的“双峰”垂直剖面的气溶胶安乐。我们将上峰（大约100 hPa，在早期的ATAL期间占主导地位，例如，在六月）干燥的气溶胶，可能来自核化过程，和较低的峰值（约250百帕，主要为一个发展良好和后期的ATAL，例如，在七月和八月）与对流云相关的云载气溶胶。我们发现，矿物粉尘（目前在两个高峰）是占主导地位的气溶胶质量在ATAL，表现出很大的年际变化，但没有长期的趋势，由于其自然变化。120至80 hPa（干气溶胶峰值）之间的结果表明，对于灰尘以外的气溶胶，ATAL由约40%的硫酸盐、30%的次生有机气溶胶和15%的原生有机气溶胶、14%的铵气溶胶和不到3%的黑碳组成。MAM 7未考虑硝酸盐气溶胶。对人为和生物质燃烧气溶胶的分析表明，CESM-MAM 7模拟的所有气溶胶都有积极的趋势。
Abstract. The Asian summer monsoon (ASM) traps convectively lifted boundary layer pollutants inside its upper-tropospheric lower-stratospheric Asian monsoon anticyclone (AMA). It is associated with a seasonal and spatially confined enhanced aerosol layer, called the Asian Tropopause Aerosol Layer (ATAL). Due to the dynamical variability of the AMA, the dearth of in situ observations in this region, the complexity of the emission sources and of transport pathways, knowledge of the ATAL properties in terms of aerosol budget, chemical composition, as well as its variability and temporal trend is still largely uncertain. In this work, we use the Community Earth System Model (CESM 1.2 version) based on the coupling of the Community Atmosphere Model (CAM5) and the MAM7 (Modal Aerosol Model) aerosol module to simulate the composition of the ATAL and its decadal trends. Our simulations cover a long-term period of 16 years from 2000 to 2015. We identify a typical “double-peak” vertical profile of aerosols for the ATAL. We attribute the upper peak (around 100 hPa, predominant during early ATAL, e.g., in June) to dry aerosols, possibly from nucleation processes, and the lower peak (around 250 hPa, predominant for a well-developed and late ATAL, e.g., in July and August) to cloud-borne aerosols associated with convective clouds. We find that mineral dust (present in both peaks) is the dominant aerosol by mass in the ATAL, showing a large interannual variability but no long-term trend, due to its natural variability. The results between 120 and 80 hPa (dry aerosol peak) suggest that for aerosols other than dust the ATAL is composed of around 40 % of sulfate, 30 % of secondary and 15 % of primary organic aerosols, 14 % of ammonium aerosols and less than 3 % of black carbon. Nitrate aerosols are not considered in MAM7. The analysis of the anthropogenic and biomass burning aerosols shows a positive trend for all aerosols simulated by CESM-MAM7.