Interannual Variability of the North Pacific Mixed Layer Associated with the Spring Tibetan Plateau Thermal Forcing
Interannual Variability of the North Pacific Mixed Layer Associated with the Spring Tibetan Plateau Thermal Forcing
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DOI：
10.1175/jcli-d-18-0577.1
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发表时间：
2019-05
影响因子：
4.9
通讯作者：
R. Sun;A. Duan;Lilan Chen;Yanjie Li;Zhiang Xie;Yu Zhao
中科院分区：
文献类型：
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作者：
R. Sun;A. Duan;Lilan Chen;Yanjie Li;Zhiang Xie;Yu Zhao
利用耦合模式CESM1.2.0的多源资料和两组敏感性试验，研究了青藏高原春季（3、4、5月）地面感热对北太平洋海温和混合层年际变化的影响。结果表明，一次偏高的MAM副高可以在下游产生Rossby波，在北太平洋形成异常的等效正压反气旋，引起反气旋风应力异常。由于Ekman输运和Ekman泵吸作用，海流在40°N附近汇聚，并伴有弱的下沉运动。混合层热量收支诊断表明，净热通量，以及纬向平流异常，在混合层温度（MLT）的变化作出了显着的贡献。结果表明，海温距平和MLT距平均呈马蹄形分布。此外，显着的温暖的SSTA显示在晚春的最大值，但显着的温暖的MLT异常集中在海面下（25米深度）可以持续到夏季，作为一个异常的春季SHTP的信号存储。此外，中纬度海气相互作用对北太平洋异常反气旋的发展也有正反馈作用，SSTA型可以加强海洋锋，诱发更为活跃的瞬变涡动活动。在总的大气强迫中占主导地位的涡动涡度强迫往往会产生一个相当的正压大气高压，这反过来又加强了初始的异常反气旋。
By using multisourced data and two sets of sensitivity runs from the coupled general circulation model CESM1.2.0, we investigated the effects of the spring [March, April, and May (MAM)] surface sensible heating over the Tibetan Plateau (SHTP) on the interannual variability of the North Pacific Ocean sea surface temperature (SST) and mixed layer. The results indicated that an above-normal MAM SHTP can generate a Rossby wave downstream and form an anomalous equivalent barotropic anticyclone over the North Pacific, inducing anticyclonic wind stress anomalies. As a result of Ekman transport and Ekman pumping, sea currents converge near 40°N, accompanied by weak downwelling motion. The mixed layer heat budget diagnosis indicates that the net heat fluxes, together with meridional advection anomalies, contributed significantly to changes in the mixed layer temperature (MLT). As a result, the SST anomalies (SSTAs) and MLT anomalies both present a horseshoelike pattern. In addition, the significant warm SSTAs show a maximum in the late spring, but the significant warm MLT anomalies centered under the sea surface (25-m depth) could be sustained until summer, acting like a signal storage for the anomalous spring SHTP. Moreover, the midlatitude ocean–atmosphere interaction provides a positive feedback on the development of the anomalous anticyclone over the North Pacific, since the SSTA pattern could strengthen the oceanic front and induce more active transient eddy activities. The eddy vorticity forcing that is dominant among the total atmospheric forcings tends to produce an equivalent barotropic atmospheric high pressure, which in turn intensifies the initial anomalous anticyclone.