Varying stratospheric responses to tropical Atlantic SST forcing from early to late winter
Varying stratospheric responses to tropical Atlantic SST forcing from early to late winter
复制标题
冬初至冬末平流层对热带大西洋海温强迫的不同反应
DOI：
10.1007/s00382-017-3998-x
复制
发表时间：
2018
期刊：
影响因子：
4.6
通讯作者：
Ren Rongcai
中科院分区：
文献类型：
--
作者：
Rao Jian;Ren Rongcai
利用多个再分析数据集和模式模拟，我们首先分离出独立于ENSO的热带大西洋（TAO）海表温度（SST）信号，然后研究它们对北部冬季平流层的影响。结果表明，TAO海温强迫确实对北方冬季平流层有显著影响，但这些影响在冬初和冬末之间存在差异，这在一定程度上解释了考虑季节平均值时整体影响不显著的原因。在暖TAO年，平流层极涡在11 - 12月异常偏弱/偏暖，1 - 3月异常偏强/偏冷，4 - 5月异常偏弱/偏暖。TAO强迫对温带平流层的不同影响与寒季温带对流层对TAO强迫的三阶段响应有关。对流层环流在初冬表现为负的北大西洋涛动响应，在冬中后期表现为向东传播的rosby波型，春季表现为北美上空经向偶极子。与此相关的是平流层中行星波活动的变化，表现为初冬增加，冬中至冬末减少，春季再次增加。三个再分析数据集和模式模拟（完全耦合模式及其分量AGCM）一致证实了TAO强迫对平流层环流的变化调制。该验证鲁棒性的一个例外是，完全耦合模式中的环极风响应相对较弱，其分量AGCM出现的时间比观测到的晚一个月。
Using multiple reanalysis datasets and model simulations, we begin in this study by isolating the tropical Atlantic Ocean (TAO) sea surface temperature (SST) signals that are independent from ENSO, and then investigate their influences on the northern winter stratosphere. It is revealed that TAO SST forcing does indeed have significant effects on the northern winter stratosphere, but these effects vary from early to late winter in a way that explains the overall insignificant effect when the seasonal average is considered. The stratospheric polar vortex is anomalously weaker/warmer in November–December, stronger/colder in January–March, and weaker/warmer again in April–May during warm TAO years. The varying impacts of the TAO forcing on the extratropical stratosphere are related to a three-stage response of the extratropical troposphere to the TAO forcing during cold season. The tropospheric circulation exhibits a negative North Atlantic Oscillation–like response during early winter, an eastward propagating Rossby wave pattern in mid-to-late winter, and a meridional dipole over North America in spring. Associated with this is varying planetary wave activity in the stratosphere, manifested as an increase in early winter, a decrease in mid-to-late winter, and an increase again in spring. The varying modulation of stratospheric circulation by TAO forcing is consistently confirmed in three reanalysis datasets, and model simulations (fully coupled model and its component AGCM). The exception to the robustness of this verification is that the circumpolar wind response in the fully coupled model is relatively weaker, and that in its component AGCM appears a month later than observed.