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Observational evidence of seasonality in the timing of loop current eddy separation

机译：环流涡流分离时间季节性的观测证据

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摘要

Observational datasets, reports and analyses over the time period from 1978 through 1992 are reviewed to derive pre-altimetry Loop Current (LC) eddy separation dates. The reanaly-sis identified 20 separation events in the 15-year record. Separation dates are estimated to be accurate to approximately +/- 1.5 months and sufficient to detect statistically significant LC eddy separation seasonality, which was not the case for previously published records because of the misidentification of separation events and their timing. The reanalysis indicates that previously reported LC eddy separation dates, determined for the time period before the advent of continuous altimetric monitoring in the early 1990s, are inaccurate because of extensive reliance on satellite sea surface temperature (SST) imagery. Automated LC tracking techniques are used to derive LC eddy separation dates in three different altimetry-based sea surface height (SSH) datasets over the time period from 1993 through 2012. A total of 28-30 LC eddy separation events were identified in the 20-year record. Variations in the number and dates of eddy separation events are attributed to the different mean sea surfaces and objective-analysis smoothing procedures used to produce the SSH datasets. Significance tests on various altimetry and pre-altimetry/altimetry combined date lists consistently show that the seasonal distribution of separation events is not uniform at the 95% confidence level. Randomization tests further show that the seasonal peak in LC eddy separation events in August and September is highly unlikely to have occurred by chance. The other seasonal peak in February and March is less significant, but possibly indicates two seasons of enhanced probability of eddy separation centered near the spring and fall equinoxes. This is further quantified by objectively dividing the seasonal distribution into two seasons using circular statistical techniques and a k-means clustering algorithm. The estimated spring and fall centers are March 2nd and August 23rd, respectively, with season boundaries in May and December. (C) 2016 Elsevier B.V. All rights reserved.
机译：回顾了1978年至1992年这段时间内的观测数据集，报告和分析，以得出高程前的环流（LC）涡流分离日期。重新分析在15年的记录中确定了20个分离事件。据估计，分离日期的准确度约为+/- 1.5个月，足以检测具有统计意义的LC涡流分离季节，由于对分离事件及其时间的错误识别，以前发布的记录并非如此。重新分析表明，由于广泛依赖于卫星海面温度（SST）图像，因此先前报告的LC涡流分离日期（在1990年代初进行连续高空监测之前的时间段内确定）不准确。自动化LC追踪技术用于在1993年至2012年的三个不同的基于测高仪的海面高度（SSH）数据集中得出LC涡旋分离日期。在20-年度记录。涡旋分离事件的数量和日期的变化归因于不同的平均海面和用于生成SSH数据集的客观分析平滑程序。对各种测高仪和测高仪/测高仪组合日期列表的显着性测试一致表明，分离事件的季节性分布在95％的置信度水平上并不均匀。随机试验进一步表明，在8月和9月发生LC涡流分离事件的季节性高峰极不可能是偶然发生的。在二月和三月的另一个季节高峰不那么重要，但是可能表明在春季和秋季春分附近集中了两个季节，涡旋分离的可能性增加。通过使用循环统计技术和k-means聚类算法将季节分布客观地分为两个季节，可以进一步对此进行量化。估计的春季和秋季中心分别是3月2日和8月23日，季节界限在5月和12月。 （C）2016 Elsevier B.V.保留所有权利。

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