New insights into precipitation development as affected by novel investigations on the limitation of large raindrops' sizes

为了实现改善降水预报的最终目标，我们重新研究了限制大雨滴尺寸（碰撞引起的破裂）的基本机制，该机制在过去仅通过极少数实验室实验进行了检验。其影响是通过使用德国气象局的云解析业务天气预报模型进行数值研究来估计的。这些研究分为两部分：首先使用先进的流体动力学代码进行数值实验，其中最详细地跟踪碰撞和碰撞大（雨）滴的破碎。它们将通过实验室实验进行检查。如果过去几次实验的结果得到证实，这些结果提供的特征的值可能取决于特定的分解模式。新数据将用于 ID-rainshaft 模型。除了在与降水物理学相关的许多领域（例如雷达气象学）中很重要的平衡雨滴尺寸谱之外，雨轴模型还提供了用于推导分裂（更粗略）参数化的基本值。根据后者的值，然后为操作应用程序开发新的分解参数化。它将取代传统的公式，该公式实际上是已经在德国气象局天气预报模型的云解析版本中运行的批量云微物理方案的一部分。将进行首次敏感性研究，以评估破碎过程的新数据对降水的影响。

To the ultimate goal to improve precipitation forecasts a basic mechanism limiting the size of large raindrops (collision-induced breakup), which has been examined in the very past by very few laboratory experiments only, is re-investigated. Its effect is estimated by numerical studies using a cloud-resolving operational weather forecast model of the German Weather Service. The studies are partitioned into two parts: At first numerical experiments with an advanced fluid-dynamics code were performed where the collision and the breakup of colliding large (rain)drops are followed in greatest detail. They will be checked by according laboratory experiments. The results provide characteristics whose values may depend on specific breakup modes if results of the few past experiments are confirmed. The new data will be used in a ID-rainshaft model. Besides equilibrium raindrop size spectra important in many fields related to precipitation physics as, e.g., in radar meteorology, the rainshaft model delivers basic values for deriving a (coarser) parameterization of breakup. Prom the latter values then a new parameterization of breakup is developed for operational applications. It will replace the traditional formulation which actually is part of a bulk cloudmicrophysical scheme running already in a cloud-resolving version of a weather forecast model of the German Weather Service. First sensitivity studies will be undertaken to assess the effect of the new data on the breakup process on precipitation.