两类El Nio对应的印度洋偶极子事件的比较研究

• 作 者: 钱景 李崇银 谭言科 桂发银 黎鑫
• 机 构: 解放军理工大学气象海洋学院,LASG国家重点实验室/中国科学院大气物理研究所,
• 出 处: 热带气象学报
• 发表日期: 2017年04期
• 关键词: 西北印度洋 东南印度洋 海温 IOD 季节演变 El Ni 偶极子 正异常 上空 大气环流异常

利用多种大气和海洋再分析资料,采用合成分析及2.5层简化海洋模型数值模拟等方法,研究了1951—2012年期间,与东部和中部型El Nio事件相伴随的热带印度洋海温偶极子(Indian Ocean Dipole,IOD)出现时,热带印度洋海温异常增暖及其上空海气耦合特征的物理机制。结果表明:夏秋季节,伴随东部型El Nio而发生的IOD事件(EP-IOD)和伴随中部型El Nio而发生的IOD事件(CP-IOD)中,热带印度洋海温正异常的强度与空间分布具有很大差异。对于EP-IOD事件,夏季,海温正异常中心最先出现在热带西北印度洋;随后秋季,海温正异常向东南发展并扩大至热带中南印度洋,强度较强。对于CP-IOD事件,夏季和秋季,海温正异常中心都位于热带中南印度洋,呈东西向带状分布,但海温正异常强度较EP-IOD事件中弱。进一步分析表明,在EP-IOD事件中,夏季,热带西北印度洋海区西南季风偏弱,通过影响夹卷混合过程导致热带西北印度洋海温上升;秋季,热带西北印度洋上空的异常偏东风导致垂向夹卷混合的正异常,对热带西北印度洋增暖的维持起到重要作用;热带中南印度洋的增暖主要受赤道东南印度洋西传的暖性Rossby波影响。而在CP-IOD事件中,夏秋两季,热带中南印度洋海区出现显著的西北风异常,其上空风速的负异常是增温的主要原因;同时赤道东南印度洋西传的暖性Rossby波对热带中南印度洋的增暖也起到重要作用。

Based on a variety of atmospheric and ocean reanalysis data and synthetic analysis and 2.5-layer simplified numerical simulation of ocean models, we studied the correlation between the tropical Indian Ocean temperature with the El Nio events of the eastern and central regions over the 1951-2012 period When the Indian Ocean Dipole (IOD) appears, the physical mechanism of the anomalous warming of the SST over the tropical Indian Ocean and the coupling of its over-air-sea-atmosphere features. The results show that in the summer and autumn seasons, in the IOD event (EP-IOD) accompanied by the eastern El Nio and in the IOD event (CP-IOD) accompanied by the central El Nio, the positive tropical anomalies in the Indian Ocean Intensity and spatial distribution are quite different. For the EP-IOD event, the positive SST anomalies first appeared in the tropical Northwest Indian Ocean in summer. Later in the autumn, SST anomalies developed southeastward and expanded to the tropical central-southern Indian Ocean with strong intensity. For the CP-IOD event, the positive SST anomalies in summer and autumn are all located in the tropical central-southern Indian Ocean and distributed in an east-west band. However, the anomalous SST anomalies are weaker than those in the EP-IOD event. Further analysis shows that in the summer of EP-IOD, the southwesterly monsoon over the tropical Northwest Indian Ocean weakens, and the sea surface temperature rises in the tropical Northwest Indian Ocean by affecting the entrainment mixing process. In the autumn, the anomalous easterly wind over the tropical Northwest Indian Ocean leads to vertical clips The positive anomalies of volume mixing play an important role in the warming of the tropical Northwest Indian Ocean. The warming of the tropical central-southern Indian Ocean is mainly affected by the warm Rossby waves westward of the equatorial South-East Indian Ocean. In the CP-IOD event, significant northwesterly anomalies occurred in the tropical central and southern Indian Ocean over the summer and autumn. The negative anomalies of the wind speed over the tropical central-southern Indian Ocean were the main causes of warming. At the same time, warm Rossby waves westward from the equatorial Southeast Indian Ocean, The warming of the Indian Ocean also plays an important role.