Subtropical Dipole Modes Simulated in a Coupled General Circulation Model
Subtropical Dipole Modes Simulated in a Coupled General Circulation Model
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DOI：
10.1175/jcli-d-11-00396.1
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发表时间：
2012-06
影响因子：
4.9
通讯作者：
Y. Morioka;T. Tozuka;S. Masson;P. Terray;Jing‐Jia Luo;T. Yamagata
中科院分区：
文献类型：
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作者：
Y. Morioka;T. Tozuka;S. Masson;P. Terray;Jing‐Jia Luo;T. Yamagata
利用最初为预测热带气候变化而开发的耦合大气环流模式的结果，研究了南印度洋和南大西洋副热带偶极子模态的增长和衰减机制及其对南部非洲降雨的影响。南印度洋（南大西洋）海表温度（SST）年际变化的第二（最）主要模态呈现东北 - 西南向的偶极子，现称为副热带偶极子模态。正（负）的海表温度年际异常极在南半球春季开始增长，并在2月达到峰值。在南半球晚春，与副热带高压变化相关的潜热通量损失受到抑制（增强），导致混合层厚度比正常情况更薄（更厚），进而增强（减弱）了气候短波辐射对混合层的加热。正（负）极在南半球秋季逐渐衰减，因为夹卷作用对混合层的冷却增强（减弱），这主要是由于混合层和夹卷水之间的温差更大（更小）。由于海表温度升高（降低）导致的潜热损失增加（减少）也有助于正（负）极的衰减。尽管需要使用更长的观测数据进行进一步验证，但目前的耦合模式表明，南大西洋副热带偶极子在南部非洲地区降雨变化中可能比印度洋副热带偶极子发挥更重要的作用。
The growth and decay mechanisms of subtropical dipole modes in the southern Indian and South Atlantic Oceans and their impacts on southern African rainfall are investigated using results from a coupled general circulationmodeloriginallydevelopedforpredictingtropicalclimatevariations.Thesecond(most)dominant mode of interannual sea surface temperature (SST) variations in the southern Indian (South Atlantic) Ocean represents a northeast‐southwest oriented dipole, now called subtropical dipole mode. The positive (negative) SST interannualanomalypole startsto grow in australspring and reachesits peakin February.In austral late spring, the suppressed (enhanced) latent heat flux loss associated with the variations in the subtropical high causes a thinner (thicker) than normal mixed layer thickness that, in turn, enhances (reduces) the warming of the mixed layer by the climatological shortwave radiation. The positive (negative) pole gradually decays in austral fall because the mixed layercooling by the entrainmentis enhanced(reduced),mostlyowing to the larger (smaller) temperature difference between the mixed layer and the entrained water. The increased (decreased) latent heat loss due to the warmer (colder) SST also contributes to the decay of the positive (negative) pole. Although furtherverification using longerobservational data is required,the present coupled model suggests that the South Atlantic subtropical dipole may play a more important role in rainfall variations over the southern African region than the Indian Ocean subtropical dipole.