Higher ocean wind speeds during marine cold air outbreaks
Higher ocean wind speeds during marine cold air outbreaks
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DOI：
10.1002/qj.3068
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发表时间：
2017-07
影响因子：
8.9
通讯作者：
Erik W. Kolstad
中科院分区：
文献类型：
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作者：
Erik W. Kolstad
海洋冷空气爆发(MCAO)是指冷气团平流到公海上空的大规模事件。众所周知，这些事件与极地低压的形成和与高风速有关的其他中尺度现象有关，因此在某些情况下对海洋活动构成危险。然而，MCAO是否总体上有利于风速高于正常水平仍是个未知数。在这里，通过比较不同水平网格间距的大气再分析产品中MCAO期间的海洋近地表风速，以及使用允许对流的数值天气预报模式的两个案例来研究这一点。研究区域是拉布拉多海和格陵兰-冰岛-挪威(GIN)海，那里的MCAO已被证明对海-气相互作用和深水形成具有重要作用。其中一个主要发现是，在最强的MCAO事件期间，风速高于正常，在不太严重的事件中，风速高于风速。来自案例研究的有限证据表明，网格间距超过50公里的重新分析低估了MCAO期间由大的海洋-大气能量通量驱动的风。MCAO的高峰期通常出现在斜压波经过该区域时。因此，MCAO期间的大风时段一般只持续几天。然而，这里定义的MCAO可以持续50天或更长时间。
Marine cold air outbreaks (MCAOs) are large‐scale events in which cold air masses are advected over open ocean. It is well‐known that these events are linked to the formation of polar lows and other mesoscale phenomena associated with high wind speeds, and that they therefore in some cases represent a hazard to maritime activities. However, it is still unknown whether MCAOs are generally conducive to higher wind speeds than normal. Here this is investigated by comparing ocean near‐surface wind speeds during MCAOs in atmospheric reanalysis products with different horizontal grid spacings, along with two case‐studies using a convection‐permitting numerical weather prediction model. The study regions are the Labrador Sea and the Greenland–Iceland–Norwegian (GIN) Seas, where MCAOs have been shown to be important for air–sea interaction and deep water formation. One of the main findings is that wind speeds during the strongest MCAO events are higher than normal and higher than wind speeds during less severe events. Limited evidence from the case‐studies suggests that reanalyses with grid spacings of more than 50 km underestimate winds driven by the large ocean–atmosphere energy fluxes during MCAOs. The peak times of MCAOs usually occur when baroclinic waves pass over the regions. Therefore, the strong wind episodes during MCAOs generally last for just a few days. However, MCAOs as defined here can persist for 50 days or more.