The roles of static stability and tropical-extratropical interactions in the summer interannual variability of the North Atlantic sector
The roles of static stability and tropical-extratropical interactions in the summer interannual variability of the North Atlantic sector
复制标题
静态稳定性和热带-温带相互作用在北大西洋扇区夏季年际变化中的作用
DOI：
10.1007/s00382-018-4192-5
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发表时间：
2018
期刊：
影响因子：
4.6
通讯作者：
Mbengue C
中科院分区：
文献类型：
--
作者：
Mbengue C
北大西洋地区夏季季节预报技能低于冬季技能。为了确定对可预测性的潜在控制，对北大西洋斜压性对大气驱动因素的敏感性进行了量化。使用 ERA-INTERIM 再分析数据，北大西洋风暴路径斜压性对夏季经向温度梯度变化不太敏感。静态稳定性通过调节斜压性对经向温度梯度和对流层顶高度变化的敏感性以及修改斜压性本身来塑造该部门的年际变化。高层的高静态稳定性异常导致夏季不列颠群岛上空出现更多的纬向温带气旋路径和更高的涡流动能。这些静稳定异常与夏季NAO没有很强的相关性；但它们与热带大西洋上空对流的抑制和向极地移动的副热带急流有关。这些结果表明北大西洋变化的非本地驱动因素。此外，它们意味着北美东南部和热带大西洋对流表征的改进可能会提高夏季季节预报技能。
Summer seasonal forecast skill in the North Atlantic sector is lower than winter skill. To identify potential controls on predictability, the sensitivity of North Atlantic baroclinicity to atmospheric drivers is quantified. Using ERA-INTERIM reanalysis data, North Atlantic storm-track baroclinicity is shown to be less sensitive to meridional temperature-gradient variability in summer. Static stability shapes the sector’s interannual variability by modulating the sensitivity of baroclinicity to variations in meridional temperature gradients and tropopause height and by modifying the baroclinicity itself. High static stability anomalies at upper levels result in more zonal extratropical cyclone tracks and higher eddy kinetic energy over the British Isles in the summertime. These static stability anomalies are not strongly related to the summer NAO; but they are correlated with the suppression of convection over the tropical Atlantic and with a poleward-shifted subtropical jet. These results suggest a non-local driver of North Atlantic variability. Furthermore, they imply that improved representations of convection over the south-eastern part of North America and the tropical Atlantic might improve summer seasonal forecast skill.