Impacts of Number of Cloud Condensation Nuclei on Two-Dimensional Moist Rayleigh Convection
Impacts of Number of Cloud Condensation Nuclei on Two-Dimensional Moist Rayleigh Convection
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DOI：
10.2151/jmsj.2020-023
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发表时间：
2020-02
期刊：
影响因子：
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通讯作者：
Y. Miyamoto;S. Nishizawa;H. Tomita
中科院分区：
文献类型：
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作者：
Y. Miyamoto;S. Nishizawa;H. Tomita
研究了云凝结核（CCN）数密度和其他热力学量对湿瑞利对流的影响。开发了一个数值模型，由布辛涅斯克空气的简单二维方程和复杂的双矩微物理方案组成。 CCN数量的影响在最初形成的对流中最为突出，而准稳态的对流并不显着依赖于CCN的数量。有人认为，前者的对流是由没有背景环流的机制驱动的，例如包裹理论。相反，后者的对流似乎是由静态不稳定的背景层驱动的。结合云微物理降低了对流细胞的积分动能和数量（增加了细胞之间的距离），但有一些例外，这与之前的研究一致。这些特征对 CCN 的数量不太敏感。研究表明，动能的减少主要是由于上（下）层的凝结（蒸发），这往往使流体趋于稳定。集合模拟表明，潮湿过程对底部边界温度、温度递减率、水汽混合比和CCN变化的敏感性与控制模拟定性相似。随着温度下降率的增加，影响变得更强。域中的对流细胞数量随着过饱和程度或域集成冷凝物的增加而减少。
The impacts of the number density of cloud condensation nuclei (CCN) and other thermodynamic quantities on moist Rayleigh convection were examined. A numerical model, consisting of a simple two–dimensional equation for Boussinesq air and a sophisticated double moment microphysics scheme, was developed. The impact of the number of CCN is most prominent in the initially formed convection, whereas the convection in the quasi–steady state does not significantly depend on the number of CCN. It is suggested that the former convection is driven by a mechanism without a background circulation, such as parcel theory. In contrast, the latter convection appears to be driven by the statically unstable background layer. Incorporating the cloud microphysics reduces the integrated kinetic energy and number of convective cells (increases the distance between the cells), with some exceptions, which are consistent with previous studies. These features are not largely sensitive to the number of CCN. It is shown in this study that the reduction in kinetic energy is mainly due to condensation (evaporation) in the upper (lower) layer, which tends to stabilize the fluid. The ensemble simulation shows that the sensitivity of the moist processes to changes in the temperature at the bottom boundary, temperature lapse rate, water vapor mixing ratio, and CCN is qualitatively similar to that in the control simulation. The impact becomes strong with increasing temperature lapse rate. The number of convective cells in a domain decreases with the degree of supersaturation or an increase in the domain-integrated condensate.