Opinion: A critical evaluation of the evidence for aerosol invigoration of deep convection
Opinion: A critical evaluation of the evidence for aerosol invigoration of deep convection
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DOI：
10.5194/acp-23-13791-2023
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发表时间：
2023-11
影响因子：
6.3
通讯作者：
A. Varble;A. Igel;H. Morrison;W. Grabowski;Z. Lebo
中科院分区：
文献类型：
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作者：
A. Varble;A. Igel;H. Morrison;W. Grabowski;Z. Lebo
抽象的。通过增加气溶胶数浓度对云微物理学的间接影响，深对流上升气流活跃经常被引用为气溶胶和深对流特性之间相关性的驱动因素。在这里，我们批判性地评估理论，建模和观测证据的温暖和冷相振兴途径。虽然暖相增强是合理的，并通过在污染条件下增加云滴浓度降低过饱和度在理论上得到支持，但这种效应的重要性取决于尚未观察到的真实对流云中的过饱和度变化。大部分的理论支持冷相增活取决于不切实际的假设瞬时冻结和卸载的冷凝物在增长，孤立的上升气流。当应用更现实的假设时，在污染条件下通过聚变增强潜热对浮力的影响在很大程度上被更大的冷凝物负荷所抵消。许多支持振奋精神的基础性观察研究都有几个基本的方法论缺陷，使他们的发现不正确或非常可疑。因此，大部分的证据都来自数值模拟，但不同的模型和设置产生了广泛的结果。此外，模拟气溶胶对深对流的影响很少测试的鲁棒性，微物理偏差相对于观测持续存在，使许多结果不可靠的应用到真实的世界。在没有明确的理论、模拟或观测支持的情况下，考虑到某些深对流系统和环境可能会发生衰弱而不是活跃，冷相活跃的总体影响完全可能可以忽略不计。在任何给定事件中，对流上升气流强度的主要热力学控制的中尺度变化与大量的上升气流和气溶胶变化相结合，观测结果难以量化，并对隔离气溶胶效应提出了进一步的挑战。气溶胶对流增强的观测隔离和量化也因可用云凝结核和上升气流速度代理的限制、气溶胶与气象条件的相关性以及云对气溶胶的影响而变得复杂。此外，许多云的过程，如夹带和冷凝沉降，调节上升气流的强度和气溶胶云的相互作用，云的生命周期和组织不同，但这些过程仍然很差的特点。考虑到这些挑战，建议为未来的观测和模拟研究气溶胶的深对流激活。
Abstract. Deep convective updraft invigoration via indirect effects of increased aerosol number concentration on cloud microphysics is frequently cited as a driver of correlations between aerosol and deep convection properties. Here, we critically evaluate the theoretical, modeling, and observational evidence for warm- and cold-phase invigoration pathways. Though warm-phase invigoration is plausible and theoretically supported via lowering of the supersaturation with increased cloud droplet concentration in polluted conditions, the significance of this effect depends on substantial supersaturation changes in real-world convective clouds that have not been observed. Much of the theoretical support for cold-phase invigoration depends on unrealistic assumptions of instantaneous freezing and unloading of condensate in growing, isolated updrafts. When applying more realistic assumptions, impacts on buoyancy from enhanced latent heating via fusion in polluted conditions are largely canceled by greater condensate loading. Many foundational observational studies supporting invigoration have several fundamental methodological flaws that render their findings incorrect or highly questionable. Thus, much of the evidence for invigoration has come from numerical modeling, but different models and setups have produced a vast range of results. Furthermore, modeled aerosol impacts on deep convection are rarely tested for robustness, and microphysical biases relative to observations persist, rendering many results unreliable for application to the real world. Without clear theoretical, modeling, or observational support, and given that enervation rather than invigoration may occur for some deep convective regimes and environments, it is entirely possible that the overall impact of cold-phase invigoration is negligible. Substantial mesoscale variability of dominant thermodynamic controls on convective updraft strength coupled with substantial updraft and aerosol variability in any given event are poorly quantified by observations and present further challenges to isolating aerosol effects. Observational isolation and quantification of convective invigoration by aerosols is also complicated by limitations of available cloud condensation nuclei and updraft speed proxies, aerosol correlations with meteorological conditions, and cloud impacts on aerosols. Furthermore, many cloud processes, such as entrainment and condensate fallout, modulate updraft strength and aerosol–cloud interactions, varying with cloud life cycle and organization, but these processes remain poorly characterized. Considering these challenges, recommendations for future observational and modeling research related to aerosol invigoration of deep convection are provided.