Numerical sensitivity studies on the impact of aerosol properties and drop freezing modes on the glaciation, microphysics, and dynamics of clouds
Numerical sensitivity studies on the impact of aerosol properties and drop freezing modes on the glaciation, microphysics, and dynamics of clouds
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关于气溶胶性质和液滴冻结模式对冰川作用、微物理和云动力学影响的数值敏感性研究
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
S. Wurzler
中科院分区：
文献类型：
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作者：
K. Diehl;M. Simmel;S. Wurzler
[1]通过数值模拟，研究了液滴在浸没和接触模式下的冻结效应。为了描述非均质液滴冻结，考虑到不同冰核的冰成核效率显著不同，采用了新的方法。一个气团模式与云微物理的截面二维描述。通过改变不溶性颗粒类型以及气溶胶颗粒的可溶性部分进行了敏感性研究，显示了这些参数对水滴冻结的影响及其对垂直云动力学的可能影响。可溶性部分的大小决定了是浸泡还是接触冷冻将是主要的过程。对于高的温度值，浸没冷冻是主要的过程。在这种情况下，冷冻过程强烈依赖于温度，并且不溶性颗粒类型的冰成核效率对于有效冷冻变得重要。凝固点下降可以忽略不计，因为大的液滴优先冻结。在较低的温度下，接触冻结是主要的过程。在这些情况下，冷冻过程较少依赖于温度和气溶胶颗粒类型。在有效冻结的条件下，可能会形成寒冷、高海拔、完全结冰的云。所提出的浸没和接触冻结方法可以进一步纳入中尺度和全球模式，以估计特定冰核对冰形成的影响。
[1] Numerical simulations were performed to investigate the effects of drop freezing in immersion and contact modes for a convective situation. For the description of heterogeneous drop freezing, new approaches were used considering the significantly different ice nucleating efficiencies of various ice nuclei. An air parcel model with a sectional two-dimensional description of the cloud microphysics was employed. Sensitivity studies were undertaken by varying the insoluble particle types as well as the soluble fraction of the aerosol particles showing the effects of these parameters on drop freezing and their possible impact on the vertical cloud dynamics. The soluble fraction ɛ decides whether immersion or contact freezing will be the major process. For high ɛ values, immersion freezing is the dominant process. In such cases the freezing process is strongly temperature-dependent, and the ice nucleation efficiency of the insoluble particle types becomes important for efficient freezing. The freezing point depression can be neglected because of the preferential freezing of large drops. Contact freezing is the major process in cases of lower ɛ values. In these cases the freezing process is less dependent on temperature and aerosol particle type. For conditions of efficient freezing, cold, high-altitude, completely glaciated clouds could form. The presented approaches for immersion and contact freezing can be incorporated further into mesoscale and global models to estimate the effects of specific ice nuclei on ice formation.