Dynamical proxies of North Atlantic predictability and extremes.
Dynamical proxies of North Atlantic predictability and extremes.
复制标题
北大西洋的可预测性和极端的动力代理。
DOI：
10.1038/srep41278
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发表时间：
2017-01-25
影响因子：
4.6
通讯作者：
Yiou P
中科院分区：
文献类型：
--
作者：
Faranda D;Messori G;Yiou P
大气流动的特点是混沌动力学和反复出现的大尺度模式。这两个特征表明大气吸引子的存在，洛伦兹将其定义为：“系统可以一次又一次地采取或接近的所有状态的集合，而不是那些它最终会避免的状态”。吸引子的平均尺寸 D 对应于足以描述大气环流的自由度数。然而，事实证明，获得 D 的可靠估计具有挑战性。此外，D 不提供瞬态大气运动的信息，例如导致极端天气的运动。利用动力系统理论的最新发展，我们表明可以通过吸引子的瞬时属性而不是平均属性对此类运动进行分类。瞬时特性由瞬时尺寸和稳定性唯一确定。它们的极值对应于特定的大气模式，并与极端天气事件相匹配。我们进一步表明，在两周以上的业务集合天气预报中，瞬时稳定性和维度的时间序列与海平面压力场的平均分布之间存在显着相关性。因此，吸引子的瞬时特性提供了一种评估和通知业务天气预报的有效方法。
Atmospheric flows are characterized by chaotic dynamics and recurring large-scale patterns. These two characteristics point to the existence of an atmospheric attractor defined by Lorenz as: “the collection of all states that the system can assume or approach again and again, as opposed to those that it will ultimately avoid”. The average dimension D of the attractor corresponds to the number of degrees of freedom sufficient to describe the atmospheric circulation. However, obtaining reliable estimates of D has proved challenging. Moreover, D does not provide information on transient atmospheric motions, such as those leading to weather extremes. Using recent developments in dynamical systems theory, we show that such motions can be classified through instantaneous rather than average properties of the attractor. The instantaneous properties are uniquely determined by instantaneous dimension and stability. Their extreme values correspond to specific atmospheric patterns, and match extreme weather occurrences. We further show the existence of a significant correlation between the time series of instantaneous stability and dimension and the mean spread of sea-level pressure fields in an operational ensemble weather forecast at lead times of over two weeks. Instantaneous properties of the attractor therefore provide an efficient way of evaluating and informing operational weather forecasts.