Influence of the Aleutian-Icelandic Low Seesaw and ENSO onto the Stratosphere in Ensemble Winter Hindcasts
Influence of the Aleutian-Icelandic Low Seesaw and ENSO onto the Stratosphere in Ensemble Winter Hindcasts
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DOI：
10.2151/jmsj.86.817
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发表时间：
2008-10
影响因子：
3.1
通讯作者：
Y. Orsolini;N. G. Kvamstø;I. Kindem;M. Honda;H. Nakamura
中科院分区：
文献类型：
--
作者：
Y. Orsolini;N. G. Kvamstø;I. Kindem;M. Honda;H. Nakamura
利用高分辨率(T106L60)大气环流模式(AGCM)的冬季后预报集合，研究了1978-1993年阿留申-冰岛低涡(AIS)的形成和生命周期。新提出的AIS是一种重要的变率模式，它将冬季的主要地面低气压--冰岛低气压和阿留申低气压--联系起来，从而将北太平洋和北大西洋的气候变异性联系起来。我们首次用一个平流层-对流层模式证明，存在一个相干的、集合平均的AIS延伸到平流层，它的存在调制了超长行星波的传播和极地夜间急流强度。模型AIS在2月份达到顶峰，当时阿留申和冰岛的低反相关性最大值为-0.59。AIS为描述厄尔尼诺-南方涛动(ENSO)现象对平流层的影响提供了一种新的方法。例如，厄尔尼诺条件对应于比正常阿留申低压更深的阿留申低压，将其影响扩展到冰岛部分，作为AIS负相(减弱的冰岛低压)，因此增强了行星波的垂直传播和平流层极地涡旋的减弱。AIS在冬末的这种成熟解释了平流层对ENSO响应的季节内变化，在冬末达到峰值。内部模式的可变性很大，主要在西半球发现了增强的潜在可预报性，西大西洋极大值在平流层比对流层上层更明显。
Using an ensemble of wintertime hindcasts with a high-resolution (T106L60) Atmospheric General Circulation Model (AGCM) forced by observed sea surface temperatures (SSTs) and extending into the stratosphere, we investigate the formation and lifecycle of the Aleutian-Icelandic low Seesaw (AIS) during the 1978 to 1993 period. The AIS has been newly proposed to be an important mode of variability, linking the major wintertime surface lows, the Icelandic Low and the Aleutian Low, in late winter, and thereby linking climate variability over the North Pacific and the North Atlantic. We demonstrate for the first time with a stratosphere-troposphere model, that a coherent, ensemble-mean AIS extension into the stratosphere exists, where its presence modulates ultra-long planetary wave propagation and the polar night jet intensity. The model AIS peaks in February, when the Aleutian and Icelandic Low anti-correlation maximizes at -0.59. The AIS provides a new way to describe the El Nino-Southern Oscillation (ENSO) phenomenon influence into the stratosphere. For example, El-Nino conditions correspond to a deeper than normal Aleutian Low, extending its influence into the Icelandic sector as an AIS negative phase (weakened Icelandic Low), hence enhanced planetary wave vertical propagation and a weakened stratospheric polar vortex. This maturation of the AIS in late winter explains the intra-seasonal variability of the stratospheric response to ENSO, which peaks in late winter. Internal model variability is large and enhanced potential predictability is found primarily in the western hemisphere, with a western Atlantic maxima being more pronounced in the stratosphere than in the upper troposphere.