The role of the tropical West Pacific in the extreme Northern Hemisphere winter of 2013/2014
The role of the tropical West Pacific in the extreme Northern Hemisphere winter of 2013/2014
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热带西太平洋在2013/2014年北半球极端冬季中的作用
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
T. Palmer
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文献类型：
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作者：
P. Watson;A. Weisheimer;J. Knight;T. Palmer
在2013/2014年的冬天，美国东部异常寒冷，白令海峡地区异常温暖，加州处于干旱之中，英国遭受了严重的洪水。有人认为，热带西太平洋（TWPAC）的海表温度升高是部分原因，因为它们产生了传播到热带外的Rossby波列。我们发现，热带大气放松到再分析的季节预报给出了2013/2014年冬季平均异常，与北方半球观测到的异常非常相似，表明低纬度异常在极端事件的发展中发挥了作用。仅仅放松TWPAC就会在一月份在北太平洋和北美上空产生强烈的波列，但在冬季则不然。这表明，仅该地区的异常就有很大的影响，但不能解释整个冬季的极端情况。我们还研究了应用观测到的TWPAC SST异常在两个大气环流模式的响应。我们发现，这确实产生冬季平均异常在北太平洋和北美类似的观察和热带强迫的Rossby波由于应用SST异常出现强于再分析，除了在1月。因此，这两个实验都表明TWPAC的影响是重要的，但TWPAC影响的真正强度是不确定的。没有一个实验表明TWPAC异常对欧洲有强烈的系统性影响。
In the 2013/2014 winter, the eastern U.S. was exceptionally cold, the Bering Strait region was exceptionally warm, California was in the midst of drought, and the UK suffered severe flooding. It has been suggested that elevated sea surface temperatures (SSTs) in the tropical West Pacific (TWPAC) were partly to blame due to them producing a Rossby wave train that propagated into the extratropics. We find that seasonal forecasts with the tropical atmosphere relaxed toward a reanalysis give 2013/2014 winter mean anomalies with strong similarities to those observed in the Northern Hemisphere, indicating that low‐latitude anomalies had a role in the development of the extremes. Relaxing just the TWPAC produces a strong wave train over the North Pacific and North America in January, but not in the winter mean. This suggests that anomalies in this region alone had a large influence but cannot explain the extremes through the whole winter. We also examine the response to applying the observed TWPAC SST anomalies in two atmospheric general circulation models. We find that this does produce winter mean anomalies in the North Pacific and North America resembling those observed and that the tropical forcing of Rossby waves due to the applied SST anomalies appears stronger than that in reanalysis, except in January. Therefore, both experiments indicate that the TWPAC influence was important, but the true strength of the TWPAC influence is uncertain. None of the experiments indicate a strong systematic impact of the TWPAC anomalies on Europe.