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

为了提高降水预报的最终目标，我们重新研究了限制大雨滴大小的基本机制（碰撞引起的破裂），这一机制在过去只在很少的实验室实验中得到了检验。它的影响是通过使用德国气象局的云分辨业务天气预报模式的数值研究估计的。研究分为两部分：首先用先进的流体力学代码进行了数值实验，其中最详细地跟踪了碰撞和碰撞大（雨）滴的破裂。它们将通过实验室实验进行检验。如果过去几个实验的结果得到证实，结果提供的特性值可能取决于特定的破裂模式。新数据将用于ID-rainshaft模型。除了平衡雨滴大小光谱在许多与降水物理相关的领域中很重要，例如在雷达气象学中，雨井模式为推导（更粗略的）破碎参数化提供了基本值。在此基础上，提出了一种适用于实际应用的分解参数化方法。它将取代传统的公式，而传统的公式实际上是已经在德国气象局的一个云分辨版本的天气预报模型中运行的大量云微物理计划的一部分。首先将进行敏感性研究，以评估关于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.