热带印度洋海温异常与ENSO关系的进一步研究

A study on relationship between ENSO and tropical Indian Ocean temperature.

用1955年1月—2001年12月美国Scripps海洋研究所的海温再分析资料、美国NCEP再分析资料和美国气候预测中心(CPC)资料,讨论了热带太平洋ENSO与热带印度洋海温距平以及与印度洋偶极子(Dipole)的关系,研究结果发现:在垂直最大温度距平曲面(MTAL)上,热带印度洋海温距平分布存在着与热带太平洋ENSO密切相关的Dipole现象,其中最大的相关在太平洋ENSO超前印度洋Dipole一个月。但是,热带印度洋Dipole的分布与Saij定义的位置略有不同,为东北西南向,它们分别在6°—10°S、65°—75°E(西印度洋)和2°—6°N、85°—95°E(东印度洋),它是赤道印度洋的一个主要海温距平系统。另外,在热带印度洋东北部与ENSO相关的海温距平是一个上下不一致的系统,该海温距平并没有伸展到海面,从海面到20—50m的浅薄水层,则为与赤道西南印度洋相同符号的海温距平分布。因此在海面,海温距平不存在与ENSO有关的Dipole现象,赤道印度洋Dipole只存在于次表层以下,这是赤道印度洋Dipole与ENSO不同之处。这种赤道东北印度洋表层与赤道西南印度洋表层同符号的海温距平现象,有可能是海气热力过程如感热过程造成的。热带印度洋Dipole的周期要小于ElNin^o,一般为1—6a。

The relationship between ENSO and Indian Ocean Dipole was discussed by using the data set of sea temperature from Scripps Institute of Oceanography, the air temperature at 1000 hPa from the NCEP reanalysis data and the Nino3 index from the Climate Prediction Center （CPC） of U.S.A. during the period from 1955 to 2001. The results show that there exists a Dipole on the maximum temperature anomalous level （MTAL） in the Indian Ocean, which close relates to ENSO in the Pacific Ocean. During E1 Nino periods there are good relationships between ENSO and Indian Ocean Dipole with the maximum correlation occurring when the ENSO leads by one month, but in La Nina periods the relationship is not so good. The distribution of Dipole in Indian Ocean is from northeast to southwest, with one （west） pole in 65^＊ - 75^＊E,6^＊ - 10^＊S and the other in 85^＊ - 95^＊E,2^＊ - 6^＊N, which is different from that defined by Saij. The correlation coefficients of Nino3 index with temperature anomalies in the west/east poles on the MTAL are over 0.4/- 0.15, respectively. It is a main sea temperature system in the tropical Indian Ocean. However, in the surface layer from sea surface to 20 - 30 m depth there is no such a dipole with opposite sea temperature anomalies in the NE and SW of tropical Indian Ocean. The SSTA in the NE might be influenced by the sensible exchange process because the evolution of sea and 1000 hPa air temperature anomaly time series of the NE of tropical Indian Ocean is quite similar except 1962 - 1963 and 1986. The periods of the Indian Ocean Dipole are shorter than that of ENSO, and about 1 to 6-year.