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首页> 外文期刊>Current Science: A Fortnightly Journal of Research >Indian Ocean dipole mode and tropical cyclone frequency
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Indian Ocean dipole mode and tropical cyclone frequency

机译：印度洋偶极子模式和热带气旋频率

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The Indian Ocean dipole is a coupled ocean-atmosphere phenomenon observed in the Indian Ocean (IO) in the form of an east-west dipole in the sea surface temperature (SST) anomalies. The Indian Ocean Dipole Mode Index (IODMI) is defined as the difference in SST anomaly between the tropical western IO (50-70deg E, 10deg S-10deg N) and the tropical southeastern IO (90-110deg E, 10deg S-equator). Positive IODMI is associated with warm SST anomaly over the western tropical IO and cold SST anomaly over the southeastern tropical IO. Sign of the index reverses when SST anomalies swing to the opposite phase. The IODM phenomenon seems to play a key role in the occurrence of droughts (Tuarang) over the Indonesian region. When IODMI is negative, it leads to drought over Indonesia and floods over East Africa and vice versa. Positive IODMI seems to correspond to more monsoon rains over India. The northeast monsoon rainfall (October-December) over south peninsular India and the IODM (September-November) are directly related, suggesting that the positive (negative) phase of the mode enhances (suppresses) the northeast monsoon activity. A recent study has shown that the Indian summer monsoon has greater influence on the IODM, than vice versa. In the present work, the relationship between the IODM and cyclone frequency in the Bay of Bengal (BOB) during the postmonsoon season (October-December), which is also known as the storm season in South Asia, has been investigated. Monthly time-series of IODMI from January 1958 to December 2002 has been used to determine the correlation with cyclone frequencies. The cyclone frequency data have been obtained from IMD records. As mentioned earlier, the postmonsoon season from October to December is known for maximum number of intense cyclones in the north IO. Monthly frequency of severe cyclones (with maximum sustained wind speed exceeding 48 nmile per h) is highest during November. As about 80% of the north IO tropical cyclones form in the BOB, the focus of the present work is on the relationship between the IODM and the tropical cyclone frequency in the BOB.
机译：印度洋偶极子是在印度洋（IO）中观察到的一种海洋-大气耦合现象，呈海面温度（SST）异常中的东西向偶极子的形式。印度洋偶极子模式指数（IODMI）定义为热带西部IO（50-70deg E，10deg S-10deg N）和热带东南IO（90-110deg E，10deg S赤道）之间的海温异常差异。 IODMI正值与西部热带IO上的暖SST异常和东南热带IO上的冷SST异常相关。当SST异常摆动到相反相位时，索引的符号反转。 IODM现象似乎在印度尼西亚地区干旱的发生（Tuarang）中起关键作用。如果IODMI为负数，则将导致印度尼西亚的干旱和东非的洪水，反之亦然。 IODMI的上升似乎与印度季风降雨更多有关。印度南部半岛北部的东北季风降雨（10月至12月）和IODM（9月至11月）直接相关，这表明该模式的正（负）相增强（抑制）了东北季风活动。最近的一项研究表明，印度夏季风对IODM的影响要大得多，反之亦然。在目前的工作中，已经研究了季风季节（10月至12月）期间IODM与孟加拉湾（BOB）气旋频率之间的关系，该季节也称为南亚风暴季节。 1958年1月至2002年12月的IODMI每月时间序列已用于确定与气旋频率的相关性。旋风频率数据已从IMD记录中获得。如前所述，十月份至十二月的季风季节以北部IO的最大强气旋数量而闻名。十一月期间，严重旋风的月度频率（最大持续风速超过每小时48海里）最高。由于BOB中约有80％的北部IO热带气旋形成，因此目前的工作重点是IODM与BOB中热带气旋频率之间的关系。

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