Predictability of Rossby wave packets: Climatology and dynamical characteristics

Rossby波对地球大气动力学具有根本的重要性，中纬度天气系统通常嵌入在不同的Rossby波包（RWP）中。这些波包对天气预报的重要性早已得到承认，并特别注意RWP作为高影响天气事件的前兆的作用。一般来说，可以预期的是，RWP，作为大规模的流动功能服从平衡的动力学，表现出很大程度的可预测性，这可能会继承嵌入式，较小规模的天气特征。另一方面，最近的一些研究表明，预测误差和预测不确定性在RWP中传播和放大，严重影响可预测性。因此，出现了一个重要的问题：在哪些条件下RWP表现出高可预测性，在哪些条件下低可预测性？本文提出的工作将大大有助于回答这个问题。我们建议使用30年集合再预报数据集从气候学的角度来研究RWP的可预报性。我们的方法认为RWPs是不同的，物理上有意义的实体，可以通过特定的特征来描述：幅度，大小，形状和位置，这些特征的可预测性将从集合数据进行评估。将研究可预测性随季节、地理区域、持续时间和RWP生命周期阶段的变化。这种现象学的调查将补充的RWP动力学的过程为基础的调查。我们的目标是对比RWP的动态与高和低的可预测性，分别，从而更好地了解RWP的可预测性的显着变化。

Rossby waves are of fundamental importance for the dynamics of the Earth's atmosphere, and midlatitude weather systems are often embedded in distinct Rossby wave packets (RWPs). The significance of these wave packets for weather forecasting has long been recognized and special attention has been given to the role of RWPs as precursors to high-impact weather events. In general, it may be expected that RWPs, as large-scale flow features obeying balanced dynamics, exhibit a large degree of predictability, which may then be inherited by embedded, smaller-scale weather features. On the other hand, a number of recent studies have demonstrated that forecast errors and forecast uncertainty propagate and amplify within RWPs, severely affecting predictability. The important question therefore arises: Under which conditions do RWPs exhibit high predictability and under which conditions low predictability? The work proposed herein will significantly contribute to answer this question. We propose to investigate RWP predictability from a climatological perspective using a 30-year ensemble reforecast dataset. Our approach considers RWPs as distinct, physically meaningful entities that can be described by specific characteristics: amplitude, size, shape, and position, Predictability of these characteristics will be assessed from the ensemble data. Variations of predictability with season, geographical region, duration, and the phase of the life cycle of the RWP will be investigated. This phenomenological investigation will be complemented by a process-based investigation of the RWP dynamics. The goal is to contrast the dynamics of RWPs with high and low predictability, respectively, and thus to better understand significant variations in RWP predictability.