流对滴滴碰撞-凝聚的影响是否是理解云层中观测到的雨水形成的关键?
Kamal Kant Chandrakar1, Hugh Morrison1, Wojciech W Grabowski1
1Mesoscale & Microscale Meteorology Laboratory, NSF National Center for Atmospheric Research, Boulder, CO 80301.
概括
云的流显著加快了雨的形成,通过增强滴滴碰撞. 这项研究证实,流凝聚是准确云模型的关键,影响雨和雨水积累.
科学领域:
- 大气科学 大气科学
- 云物理 云物理
- 气象学 天气学
背景情况:
- 雨的形成对云的生命周期,辐射强迫,天气和气候至关重要.
- 云微物理-流相互作用是复杂的,由于规模和分辨率的限制,很难准确地建模.
- 之前的研究表明,云流会通过滴碰撞凝聚增强雨水形成.
研究的目的:
- 提供关于流对云滴大小分布和雨水形成的重大影响的实质证据.
- 将高分辨率的观测与先进的模拟进行比较,以了解这些影响.
- 为了研究巨型云凝聚核 (CCN) 在雨水形成中的作用.
主要方法:
- 高分辨率观测数据的累积混凝土云.
- 最先进的大模拟器 (LES).
- 将LES与基于拉格朗的粒子的微物理学方案结合起来.
主要成果:
- 流凝聚对于准确建模观察到的滴量分布至关重要,特别是在较低的云层下降雨.
- 与仅使用重力凝聚的模拟相比,流导致较早的降雨形成和降雨积累的增加.
- 在云基附近观察到的雨水大小分布遵循一个从纯引力或简化流模型偏离的功率定律,支持流凝聚.
结论:
- 流滴凝聚是发起温暖积云中的降雨的主导因素.
- 巨型CCN对降雨形成的影响有限,原因是它们相对于云的热寿命的缓慢平衡时间.
- 准确的大气模型需要纳入流凝聚,以实现现实的云和降水模拟.
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