A new combined detection algorithm for blocking and subtropical ridges
A new combined detection algorithm for blocking and subtropical ridges
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一种新的阻塞和副热带脊联合检测算法
作者：
P. M. Sousa;D. Barriopedro;R. Garcia;T. Woollings;R. Trigo
阻塞是中/高纬度地区的高影响大气系统，在气象学和气候学研究中得到广泛讨论。然而，阻塞定义的多样性使得研究之间的比较并不简单。在这里，我们提出了一个概念模型的高压系统的生命周期，认识到这些事件的多方面和瞬态特性。一个检测方案识别和分类日常结构，区分副热带高压脊和不同类型的完善的阻塞模式（欧米茄和偶极子样雷克斯）。这是一个时空跟踪算法的补充，该算法解释了模式之间的过渡，提供了1950-2020年的全球事件目录。标准依赖于从一个单级字段中检索的简单指标，并允许在不同的数据集和气候领域中实施。使用再分析数据，我们提供了说明性的例子，第一个全球和季节性的气候评估的高压事件的多样性，其相关的影响和最近的频率changes.Results显示，脊和阻塞事件影响广泛的地区，从副热带到高纬度。我们发现显着不同的区域之间的影响所考虑的类型，这在以前的研究中受到阻碍的限制集中雷克斯样结构。这种过多的高压系统在南半球就不那么明显了，那里的活动主要是由副热带高压脊和隐蔽的阻塞模式所控制。我们报告低纬度系统的频率增加，虽然半球和季节性差异，只能部分解释为亚热带扩张的后果。阻塞频率趋势表现出更异质和复杂的空间格局，没有证据表明普遍的显着变化。
Blockings are high-impact atmospheric systems of mid/high-latitudes and have been widely addressed in meteorological and climatological studies. However, the diversity of blocking definitions makes comparison across studies not straightforward. Here, we propose a conceptual model for the life-cycle of high-pressure systems that recognizes the multifaceted and transient characteristics of these events. A detection scheme identifies and classifies daily structures, discriminating between subtropical ridges and different types of well-established blocking patterns (omega and dipole-like Rex). This is complemented by a spatio-temporal tracking algorithm, which accounts for transitions between patterns, providing a global catalogue of events for 1950-2020. Criteria rely on simple metrics retrieved from one single-level field, and allow implementation in different datasets and climatic realms. Using reanalyses data, we provide illustrative examples, the first global and seasonal climatological assessment of the diversity of high-pressure events, their associated impacts and recent frequency changes.Results reveal that ridge and blocking events affect widespread regions from the subtropics to high-latitudes. We find remarkably distinct regional impacts among the considered types, which had been hindered in previous studies by restricted focus on Rex-like structures. This plethora of high-pressure systems is much less evident in the Southern Hemisphere, where activity is dominated by subtropical ridges and secluded blocking-like patterns. We report increasing frequencies of low-latitude systems, although with hemispheric and seasonal differences that can only be partially interpreted as a consequence of subtropical expansion. Blocking frequency trends exhibit more heterogeneous and complex spatial patterns, with no evidence of generalized significant changes.