Observed and modeled tropospheric cold anomalies associated with sudden stratospheric warmings
Observed and modeled tropospheric cold anomalies associated with sudden stratospheric warmings
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DOI：
10.1002/2015jd023860
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发表时间：
2016-02
期刊：
影响因子：
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通讯作者：
Ilari Lehtonen;A. Karpechko
中科院分区：
文献类型：
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作者：
Ilari Lehtonen;A. Karpechko
根据再分析资料，分析了1958-2010年35次主要平流层突然变暖(SSW)的地面天气形势。对7个平流层分辨率地球系统模型的数据进行了类似的分析。分别对位移和分裂的SSW进行了分析。观测分析表明，在欧亚大陆北部，与SSW相关的冷异常在SSW中心日之前比事件中心日之后的前2个月更强、更广泛。对于流离失所事件来说，情况尤其如此。SSW前的冷异常与触发SSW的大气阻塞事件相耦合。虽然SSW是北半球冷空气爆发的重要预报因子，但我们的结果表明，前一次阻塞对近地表温度的影响实际上比SSW的下降影响要显著得多。因此，平流层-对流层耦合对欧亚大陆的冷空气爆发只能提供有限的可预测性。这些模式定性地再现了SSW之后典型的大尺度地面天气模式，但它们在很大程度上忽略了SSW之前欧洲和西伯利亚上空的冷却。因此，与SSW相关的最强模拟温度异常发生在事件之后。此外，模式结果还表明，分裂事件后对流层对SSW的响应较强。同时，许多模型模拟的分裂SSW太少。
Surface weather patterns related to 35 major sudden stratospheric warmings (SSWs) in 1958–2010 are analyzed based on reanalysis data. Similar analyses are conducted with data from seven stratosphere‐resolving Earth system models. The analyses are carried out separately for displacement and splitting SSWs. On the basis of the observational analysis, it is shown that in northern Eurasia, the cold anomalies linked to the SSWs tend to be stronger and more widespread before the central date of the SSWs than during the first 2 months after the event central dates. This is particularly true for the displacement events. The cold anomalies preceding the SSWs are coupled to atmospheric blocking events which trigger the SSWs. While the role of SSWs as important predictors of cold air outbreaks in the Northern Hemisphere is well recognized, our results indicate that the impact of the preceding blocking on near‐surface temperatures is, in fact, widely more significant than the downward impact of the SSWs. Thus, stratosphere‐troposphere coupling provides only limited predictability for cold air outbreaks in Eurasia. The models reproduce qualitatively well the typical large‐scale surface weather patterns following the SSWs, but they largely miss the cooling preceding the SSWs over Europe and western Siberia. Hence, the strongest modeled temperature anomalies related to the SSWs occur after the events. Moreover, the model results indicate that the tropospheric response to SSWs is stronger following split events. At the same time, many models simulate too few splitting SSWs.