Secondary organic aerosols (SOA) are large contributors to fine particle mass loading and number concentration and interact with clouds and radiation. Several processes affect the formation, chemical transformation, and removal of SOA in the atmosphere. For computational efficiency, global models use simplified SOA treatments, which often do not capture the dynamics of SOA formation. Here we test more complex SOA treatments within the global Energy Exascale Earth System Model (E3SM) to investigate how simulated SOA spatial distributions respond to some of the important but uncertain processes affecting SOA formation, removal, and lifetime. We evaluate model predictions with a suite of surface, aircraft, and satellite observations that span the globe and the full troposphere. Simulations indicate that both a strong production (achieved here by multigenerational aging of SOA precursors that includes moderate functionalization) and a strong sink of SOA (especially in the middle upper troposphere, achieved here by adding particle‐phase photolysis) are needed to reproduce the vertical distribution of organic aerosol (OA) measured during several aircraft field campaigns; without this sink, the simulated middle upper tropospheric OA is too large. Our results show that variations in SOA chemistry formulations change SOA wet removal lifetime by a factor of 3 due to changes in horizontal and vertical distributions of SOA. In all the SOA chemistry formulations tested here, an efficient chemical sink, that is, particle‐phase photolysis, was needed to reproduce the aircraft measurements of OA at high altitudes. Globally, SOA removal rates by photolysis are equal to the wet removal sink, and photolysis decreases SOA lifetimes from 10 to ~3 days. A recent review of multiple field studies found no increase in net OA formation over and downwind biomass burning regions, so we also tested an alternative, empirical SOA treatment that increases primary organic aerosol (POA) emissions near source region and converts POA to SOA with an aging time scale of 1 day. Although this empirical treatment performs surprisingly well in simulating OA loadings near the surface, it overestimates OA loadings in the middle and upper troposphere compared to aircraft measurements, likely due to strong convective transport to high altitudes where wet removal is weak. The default improved model formulation (multigenerational aging with moderate fragmentation and photolysis) performs much better than the empirical treatment in these regions. Differences in SOA treatments greatly affect the SOA direct radiative effect, which ranges from −0.65 (moderate fragmentation and photolysis) to −2 W m⁻² (moderate fragmentation without photolysis). Notably, most SOA formulations predict similar global indirect forcing of SOA calculated as the difference in cloud forcing between present‐day and preindustrial simulations.

中文翻译：

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能量百亿亿地球系统模型（E3SM）中的新SOA处理方法：强大的生产能力和接收器可控制大气SOA分布和辐射强迫

次级有机气溶胶（SOA）是导致细颗粒质量加载和数量集中的主要因素，并与云和辐射相互作用。有几种过程会影响大气中SOA的形成，化学转化和去除。为了提高计算效率，全局模型使用简化的SOA处理，这些处理通常无法捕获SOA形成的动态。在这里，我们在全球能源亿亿地球系统模型（E3SM）中测试更复杂的SOA处理，以研究模拟的SOA空间分布如何响应一些重要但不确定的过程，这些过程影响SOA的形成，去除和寿命。我们使用横跨全球和整个对流层的一系列地面，飞机和卫星观测来评估模型预测。模拟表明，既需要强大的生产能力（通过中等适度功能化的SOA前体的多代老化实现），又需要强大的SOA吸收能力（特别是在中层对流层中，通过添加粒子相光解来实现），以再现垂直方向。在几次飞机野战中测得的有机气溶胶（OA）的分布；如果没有该汇，则模拟的对流层中高层OA太大。我们的结果表明，由于SOA的水平和垂直分布的变化，SOA化学配方的变化将SOA湿去除寿命更改了3倍。在此处测试的所有SOA化学配方中，都需要一个有效的化学沉池（即粒子相光解法）来重现飞机在高海拔地区的OA测量值。在全球范围内 通过光解去除SOA的速率等于湿法去除池，光解将SOA的寿命从10天减少到〜3天。最近对多个田间研究的评论发现，在顺风和逆风生物质燃烧区净OA的形成没有增加，因此我们还测试了一种替代性的经验性SOA处理，该处理可以增加源区域附近的一次有机气溶胶（POA）排放并将POA转化为SOA老化时间范围为1天。尽管这种经验处理在模拟地表附近的OA负荷方面出奇地好，但是与飞机测量值相比，它高估了对流层中层和高层对流层的OA负荷，这很可能是由于强对流运输到了弱湿的高海拔地区造成的。在这些区域中，默认的改进模型公式（具有中等程度的断裂和光解作用的多代老化）的性能要优于经验处理。SOA处理的差异极大地影响了SOA直接辐射效果，其范围从-0.65（中度碎片和光解）到-2 W m^-2（中度破碎，无光解作用）。值得注意的是，大多数SOA公式都预测了类似的SOA全局间接强迫，其计算方式是当今模拟与工业模拟之间云强迫之间的差异。