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首页> 外文期刊>Journal of Climate >Circulation Regimes: Chaotic Variability versus SST-Forced Predictability
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Circulation Regimes: Chaotic Variability versus SST-Forced Predictability

机译：流通体制：混沌变异性与SST强制可预测性

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The circulation regimes in the Pacific-North American region are studied using the NCEP-NCAR reanalyses for the 18-winter period (1981/82-1998/99; NCEP18) and for the 54-winter period (1948/49-2001/02; NCEP54). The sampling properties of the regimes are estimated using very large ensembles (of size 55) of winter simulations made for the NCEP18 period with the atmospheric general circulation model of the Center for Ocean-Land-Atmosphere Studies, forced by observed SST and sea ice. The regimes are identified using a modified version of the k-means method. From the NCEP54 dataset a set of four clusters was found [i.e., the Alaskan ridge (AR), Arctic low (AL), Pacific trough (PT), and the Arctic high (AH)], which are significant (vis-a-vis a multinormal background), and more reproducible (within randomly chosen half-length samples) than would be expected from a multinormal process. The frequency of occurrence of the PT (AH) has increased (decreased) significantly during the past two decades. The PT cluster obtained from NCEP18 dataset more closely resembles the El Nino-forced seasonal mean pattern of recent decades than it does the traditional PNA. The GCM simulates the AR, AL, and PT clusters (but not the AH). The simulated AR and PT patterns have errors (cf. the NCEP18 results), which are outside the range of internal variability. The simulated frequency of occurrence agrees with the NCEP18 results within sampling variability. The differences in cluster properties of the PT and AR regimes between the NCEP18 and NCEP54 datasets are due to changes in SST forcing, not sampling error. Year-to-year changes in the frequency of occurrence of the PT, AL, and AR clusters in the simulations and the NCEP18 dataset are generally consistent with each other.
机译：使用NCEP-NCAR再分析研究了18个冬季（1981 / 82-1998 / 99; NCEP18）和54个冬季（1948 / 49-2001 / 02）的太平洋-北美地区的循环方式; NCEP54）。使用由观测到的海温和海冰推动的，由海洋-大气-大气研究中心提供的大气总体环流模型，针对NCEP18期间进行的冬季模拟的非常大的合奏（55号），估计了该方案的采样特性。使用k-means方法的修改版本来识别方案。从NCEP54数据集中发现了四个聚类的集合[即，阿拉斯加山脊（AR），北极低层（AL），太平洋海槽（PT）和北极高层（AH）]，这是很有意义的（相对于相对于多正态背景），并且比多正态过程所期望的重现性更高（在随机选择的半长样本内）。在过去的二十年中，PT（AH）的发生频率显着增加（减少）。与传统的PNA相比，从NCEP18数据集获得的PT群集与近几十年来厄尔尼诺现象强迫的季节性平均值模式更为相似。 GCM模拟AR，AL和PT群集（但不模拟AH）。模拟的AR和PT模式具有误差（请参见NCEP18结果），该误差不在内部可变性范围内。在采样变异性内，模拟的发生频率与NCEP18结果一致。 NCEP18和NCEP54数据集之间PT和AR方案的聚类属性的差异是由于SST强迫的变化而不是采样误差引起的。在模拟和NCEP18数据集中，PT，AL和AR群集出现频率的逐年变化通常彼此一致。

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