Impacts of Tropical North Atlantic and Equatorial Atlantic SST Anomalies on ENSO
Impacts of Tropical North Atlantic and Equatorial Atlantic SST Anomalies on ENSO
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DOI：
10.1175/jcli-d-20-0835.1
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发表时间：
2021-07-01
影响因子：
4.9
通讯作者：
Li, Tim
中科院分区：
文献类型：
--
作者：
Jiang, Leishan;Li, Tim
北半球春季和夏季热带大西洋海表温度距平(SSTA)分别表现为两种主要模式：一种是盆地升温模式，另一种是经向偶极子模式。观测和耦合模式模拟表明，前者会在随后的冬季引发太平洋拉尼娜，而后者则不会。盆地变暖强迫通过开尔文波响应和与之相关的北印度洋(NIO)和海洋大陆(MC)上的风-蒸发-SST-对流(WESC)反馈导致了拉尼娜现象。异常的Kelvin波东风与季风西风相互作用，导致NIO/MC海温异常偏暖，NIO/MC出现西北-东南向加热异常，进而诱发赤道太平洋东偏东冷SSTA。相比之下，偶极子强迫对印度洋和太平洋的影响很小，因为开尔文波抵消了大西洋的不对称加热。对热带北大西洋(TNA)和赤道大西洋(EA)海温异常模式的进一步观测和模拟研究表明，TNA(EA)强迫导致了CP型(EP型)ENSO。在这两种情况下，开尔文波响应和WESC对NIO/MC的反馈在传递大西洋的影响方面都很重要。不同之处在于不同的Rossby波响应：对于TNA强迫，赤道东太平洋(EEP)出现明显的西风异常(由于其位置偏西)，而对于EA强迫，EEP没有明显的风响应。根据混合层热量收支分析，西风异常通过异常的纬向平流和垂直平流阻止了EEP的降温趋势。
The sea surface temperature anomaly (SSTA) in the tropical Atlantic during boreal spring and summer shows two dominant modes: a basin-warming mode and a meridional dipole mode, respectively. Observational and coupled model simulations indicate that the former induces a Pacific La Nina in the succeeding winter whereas the latter cannot. The basin-warming forcing induces a La Nina through a Kelvin wave response and the associated wind-evaporation-SST-convection (WESC) feedback over the northern Indian Ocean (NIO) and Maritime Continent (MC). An anomalous Kelvin wave easterly interacts with the monsoonal westerly, leading to a warm SSTA and a northwest-southeast-oriented heating anomaly in NIO/MC, which further induces easterly and cold SSTAs over the equatorial Pacific. In contrast, the dipole forcing has little impact on the Indian and Pacific Oceans due to the offsetting of the Kelvin wave to the asymmetric Atlantic heating. Further observational and modeling studies of the tropical North Atlantic (TNA) and equatorial Atlantic (EA) SSTA modes indicate that the TNA (EA) forcing induces a CP-type (EP-type) ENSO. In both cases, the Kelvin wave response and the WESC feedback over the NIO/MC are important in conveying the Atlantic's impact. The difference lies in distinctive Rossby wave responses: a marked westerly anomaly appears in the equatorial eastern Pacific (EEP) for the TNA forcing (due to its westward location) while no significant wind response is observed in the EEP for the EA forcing. The westerly anomaly prevents a cooling tendency in the EEP through anomalous zonal and vertical advection according to a mixed layer heat budget analysis.