Impact of aerosols on ice crystal size
Impact of aerosols on ice crystal size
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DOI：
10.5194/acp-18-1065-2018
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发表时间：
2018-01
影响因子：
6.3
通讯作者：
Bin Zhao;K. Liou;Y. Gu;J. Jiang;Qinbin Li;R. Fu;Lei Huang;Xiaohong Liu;Xiangjun Shi;H. Su;C. He
中科院分区：
文献类型：
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作者：
Bin Zhao;K. Liou;Y. Gu;J. Jiang;Qinbin Li;R. Fu;Lei Huang;Xiaohong Liu;Xiangjun Shi;H. Su;C. He
气溶胶和冰云之间的相互作用是从工业化前时期到现在全球辐射强迫中最大的不确定性之一。特别是，由于观测证据有限且相互矛盾，气溶胶对冰晶有效半径（Rei）的影响高度不确定，冰晶有效半径是决定冰云净辐射效应的关键参数。在这里，我们利用 9 年的卫星观测研究了不同气象条件下气溶胶对 Rei 的影响。我们发现 Rei 对气溶胶负荷的响应受到水蒸气量以及其他几个气象参数的调节。虽然在潮湿条件下 Rei 和气溶胶负荷之间存在显着的负相关性，与液体云的“Twomey 效应”一致，但在干燥条件下两者之间存在很强的正相关性。基于云块模型的模拟表明，水蒸气调节不同冰核模式的相对重要性，导致潮湿和干燥条件之间相反的气溶胶影响。当冰云分解为深层对流产生的冰云并就地形成时，水蒸气调制对两种冰云类型仍然有效，尽管由于不同的形成机制，Rei 对气溶胶的敏感性在它们之间存在显着差异。水汽调节可以在很大程度上解释Rei在不同季节对气溶胶负荷响应的差异。水蒸气调制的正确表示对于准确估计冰云产生的气溶胶云辐射强迫至关重要。
The interactions between aerosols and ice clouds represent one of the largest uncertainties in global radiative forcing from pre-industrial time to the present. In particular, the impact of aerosols on ice crystal effective radius (Rei), which is a key parameter determining ice clouds’ net radiative effect, is highly uncertain due to limited and conflicting observational evidence. Here we investigate the effects of aerosols on Rei under different meteorological conditions using 9-year satellite observations. We find that the responses of Rei to aerosol loadings are modulated by water vapor amount in conjunction with several other meteorological parameters. While there is a significant negative correlation between Rei and aerosol loading in moist conditions, consistent with the “Twomey effect” for liquid clouds, a strong positive correlation between the two occurs in dry conditions. Simulations based on a cloud parcel model suggest that water vapor modulates the relative importance of different ice nucleation modes, leading to the opposite aerosol impacts between moist and dry conditions. When ice clouds are decomposed into those generated from deep convection and formed in situ, the water vapor modulation remains in effect for both ice cloud types, although the sensitivities of Rei to aerosols differ noticeably between them due to distinct formation mechanisms. The water vapor modulation can largely explain the difference in the responses of Rei to aerosol loadings in various seasons. A proper representation of the water vapor modulation is essential for an accurate estimate of aerosol-cloud radiative forcing produced by ice clouds.