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Influence of Three Dimensional Thermal Radiation on Cloud Droplet Growth

三维热辐射对云滴生长的影响

基本信息

批准号：
317930833
负责人：
Dr. Carolin Klinger
金额：
--
依托单位：
Meteorologisches Institut
依托单位国家：
德国
项目类别：
Research Fellowships
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/317930833?language=en
关键词：
Influence Three Dimensional Thermal Radiation

项目摘要

Solar and thermal radiation drive weather and climate and strongly affect cloud formation. However, 3D radiation effects on clouds are still poorly understood and have not been investigated systematically. Due to the complexity and the computational costs of accurate 3D radiative transport, radiation is often neglected in today's cloud resolving models or, at best, treated using a plane-parallel 1D approximation which neglects horizontal radiation transport. A better understanding of the physical processes taking place in clouds will improve cloud parameterizations in numerical weather prediction and climate models and thus improve weather and climate prediction. A fast method to calculate 3D thermal radiative transfer in cloud resolving models was developed by the proposer. This method allowed for the first time to study 3D radiation effects on cloud dynamics and microphysics in detail. First studies of the effects of 3D thermal radiation on cloud dynamics were made within the PhD thesis of the proposer. The next consequent step is to investigate the effect of 3D thermal radiation on cloud microphysics which is the aim of the proposed study. Radiative cooling at cloud sides and cloud top could speed up droplet growth significantly. The cloud side cooling is a 3D effect which cannot be accounted for with 1D radiative transfer approximations. It is possible that the radiative effect on droplet growth could close the existing gap in droplet growth theory: Diffusional droplet growth slows down considerably at about 10 micron droplet size. However, the following process of collision and coalescence only takes place when droplets have a minimum size of 20 micron. For the proposed study, a cloud particle size resolving microphysical model (bin microphysics model) is needed. The hosting group (at NOAA, Boulder) has developed such a model (TAU Cloud Microphysical Code) and has been working with it for many years. For the proposed study, the above mentioned 3D thermal radiative transfer solver will be implemented into a cloud resolving model including bin microphysics (e.g. System of Atmospheric Modeling (SAM), used by the hosting group). In a second step, simulations will be setup and performed to address the questions how 3D thermal radiation affects cloud droplet growth or the development of precipitation. Finally, the simulation results will be evaluated and the effects of 3D radiation in comparison to simulations with no-radiation or 1D-radiation have to be investigated.

太阳和热辐射驱动天气和气候，并强烈影响云的形成。然而，三维辐射对云的影响仍然知之甚少，没有进行系统的研究。由于精确的3D辐射传输的复杂性和计算成本，辐射在今天的云解析模型中经常被忽略，或者充其量使用忽略水平辐射传输的平面平行1D近似来处理。更好地了解云中发生的物理过程将改善数值天气预报和气候模式中的云参数化，从而改善天气和气候预测。提出了一种快速计算云分辨模式中三维热辐射传输的方法。这种方法首次允许详细研究云动力学和微观物理学的三维辐射效应。第一次研究三维热辐射对云动力学的影响是在博士论文中提出的。接下来的步骤是调查三维热辐射对云微物理的影响，这是拟议的研究的目的。云顶和云侧的辐射冷却能显著加速云滴的生长。云侧冷却是一种三维效应，不能用一维辐射传输近似来解释。辐射对液滴生长的影响可能会缩小液滴生长理论中存在的差距：扩散液滴的生长在约10微米的液滴尺寸时大大减慢。然而，以下碰撞和聚结过程仅在液滴具有20微米的最小尺寸时发生。对于所提出的研究，云粒子大小分辨微物理模型（箱微物理模型）是必要的。主持小组（在NOAA，博尔德）已经开发了这样一个模型（TAU云微物理代码），并已与它合作多年。对于拟议的研究，上述3D热辐射传输求解器将被实施到云解析模型中，包括bin微观物理学（例如，主办组使用的大气建模系统（SAM））。在第二步中，将设置并执行模拟，以解决3D热辐射如何影响云滴生长或降水发展的问题。最后，将评估模拟结果，并研究3D辐射与无辐射或1D辐射模拟相比的影响。