A regime analysis of Atlantic winter jet variability applied to evaluate HadGEM3‐GC2
A regime analysis of Atlantic winter jet variability applied to evaluate HadGEM3‐GC2
复制标题
用于评估 HadGEM3-GC2 的大西洋冬季急流变化状况分析
DOI：
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
R. Lee
中科院分区：
文献类型：
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作者：
G. Masato;T. Woollings;K. Williams;B. Hoskins;R. Lee
利用ERA - Interim再分析和英国气象局使用的HadGEM3 - gc2气候模式的耦合和仅大气配置，分析了冬季大西洋扇区上空涡旋驱动急流的行为。该模型以较高的精度再现了急流结构的三模态分布特征，尽管观测到其明显偏向高纬度位置。有两种不同的情况导致了这种偏见。一种情况发生在喷气机从其南部状态转移时，与重新分析相比，它在太北的地方停留了太长时间。另一个则与中纬度体系的退出有关，有太多的事件向极地而不是赤道转移。在这些转变期间，过大的对流层低层涡旋热通量可以解释急流误差，即使热通量不表现出气候偏差。有趣的是，当大气模式与观测到的海表温度（SST）相结合时，这些偏差较弱，这表明正确的海表温度分布至关重要，或者海洋-大气耦合在偏差中起关键作用。进一步的分析表明，在耦合模式中，太平洋喷气机出口偏南，这导致了大西洋偏南。墨西哥湾流地区异常温暖的海温可能与太平洋偏压一起促进了低层涡旋热通量的异常活动。
The behaviour of the eddy‐driven jet over the Atlantic sector during the winter season is analyzed for the ERA‐Interim reanalysis and the coupled and atmosphere‐only configuration of HadGEM3‐GC2—the climate model in use at the Met Office. The trimodal distribution that characterizes the jet‐stream structure in terms of its preferred locations is reproduced with good accuracy by the model, although a distinct bias towards the high‐latitude position is observed. Two different scenarios are found to contribute to this bias. One occurs when the jet shifts from its southern regime, whereby it settles too far north and for too long compared with the reanalysis. The other is associated with the exit from the central latitude regime, with too many events shifting poleward rather than equatorward. Excessively large lower tropospheric eddy heat fluxes during these transitions may account for the jet errors, even though the heat fluxes do not exhibit a climatological bias. Interestingly, these biases are weaker when the atmosphere model is forced with observed sea‐surface temperatures (SSTs), suggesting that either it is vital to have the correct SST distribution or ocean–atmosphere coupling plays a key role in the biases. Additional analysis revealed that the Pacific jet exit is biased south in the coupled model and that this contributes to the Atlantic bias. Anomalously warm SSTs in the Gulf Stream region may be acting together with the Pacific bias in fostering anomalous activity in low‐level eddy heat fluxes.
影响因子：
3.1
作者：
Franzke, Christian;Woollings, Tim;Martius, Olivia
通讯作者：
Martius, Olivia
DOI：
10.5194/gmd-2016-194-supplement
发表时间：
2017
期刊：
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影响因子：
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作者：
D. Walters;I. Boutle;M. Brooks;T. Melvin;R. Stratton;S. Vosper;H. Wells;K. Williams;N. Wood
通讯作者：
D. Walters;I. Boutle;M. Brooks;T. Melvin;R. Stratton;S. Vosper;H. Wells;K. Williams;N. Wood