Impact of Gulf Stream SST biases on the global atmospheric circulation
Impact of Gulf Stream SST biases on the global atmospheric circulation
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DOI：
10.1007/s00382-018-4083-9
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发表时间：
2018-11-01
期刊：
影响因子：
4.6
通讯作者：
Masato, Giacomo
中科院分区：
文献类型：
--
作者：
Lee, Robert W.;Woollings, Tim J.;Masato, Giacomo
英国气象局统一模式在全球耦合2（GC 2）配置有一个温暖的偏差高达近7 K的墨西哥湾流SST在冬季，这是与表面热通量的偏差，并可能在大气环流的偏差。SST偏差的作用进行了检查，重点是对流层的响应进行三个敏感性实验。SST偏差被施加在墨西哥湾流的一个小的和中等的部分，也更广泛的北大西洋模型的大气配置。在这里，我们表明，这种异常的墨西哥湾流加热（和相关的转变和变化的SST梯度）的动力学响应，以增强在墨西哥湾流的瞬态涡的垂直运动，而不是平衡加热与线性动态纬向风或纬向涡热输送。加上强加的墨西哥湾流加热偏差，响应影响对流层不仅在本地，而且在偏远地区的北方半球通过行星Rossby波响应。敏感性实验部分再现了模型耦合配置相对于大气配置和ERA中期再分析的一些差异。这些偏差可能会影响模型正确响应墨西哥湾流变化或变化的能力。因此，更好的全球预测需要特别关注减少这些海洋-大气相互作用高的地区的任何大的西边界流SST偏差。
The UK Met Office Unified Model in the Global Coupled 2 (GC2) configuration has a warm bias of up to almost 7K in the Gulf Stream SSTs in the winter season, which is associated with surface heat flux biases and potentially related to biases in the atmospheric circulation. The role of this SST bias is examined with a focus on the tropospheric response by performing three sensitivity experiments. The SST biases are imposed on the atmosphere-only configuration of the model over a small and medium section of the Gulf Stream, and also the wider North Atlantic. Here we show that the dynamical response to this anomalous Gulf Stream heating (and associated shifting and changing SST gradients) is to enhance vertical motion in the transient eddies over the Gulf Stream, rather than balance the heating with a linear dynamical meridional wind or meridional eddy heat transport. Together with the imposed Gulf Stream heating bias, the response affects the troposphere not only locally but also in remote regions of the Northern Hemisphere via a planetary Rossby wave response. The sensitivity experiments partially reproduce some of the differences in the coupled configuration of the model relative to the atmosphere-only configuration and to the ERA-Interim reanalysis. These biases may have implications for the ability of the model to respond correctly to variability or changes in the Gulf Stream. Better global prediction therefore requires particular focus on reducing any large western boundary current SST biases in these regions of high ocean-atmosphere interaction.