热带海洋SST与北半球大气环流的低频振荡特征

采用复经验正交函数展开（ＣＥＯＦ）等方法研究了热带海洋海表温度异常（ＳＳＴＡ）和北半球５００ｈＰａ高度场异常（Ｈ５００）的甚低频（ＬＦ）和准两年（ＱＢ）两种低频振荡空间振幅和位相变化，发现ＳＳＴＡ变化信号在热带西太平洋最先出现，其后是热带中东太平洋，最后是热带中东太平洋，最后是热带印度洋和南海。副热带中西太平洋Ｈ５００滞后于中东太平洋ＳＳＴＡ １￣２月，Ｈ５００的ＬＦ分量从副热带中西太平洋经西北太

THE CHARACTER OF LOW-FREQUENCY OSCILLATION IN THE TROPIC OCEAN SST AND NORTHERN HEMISPHERE ATMOSPHERE CIRCULATION

The time series of Fourier expansion and a weights filter are used in this paper toseparate two bands of low frequency, i. e. the quasi-biennial oscillation (QB) and 3-7 yearslowfrequency (LF). it is showm that both LF and QB widely exist in the both fields of tropical seasurface temperature anomaties (SSTA) and atmosphere geopotential height at 5OOhPa level (H500) inthe Northem Hemisphere, and that the fraction of total variance for LF is generally larger than thatof the QB constituent.The leading spatial struc1ure and the phase relation as concisely described by a set of complexempirical orthogonal functions (CEOF), revealed that the SST anomalies in the tropical West Pacificvaries out of phase, leading by l to 3 months those in the tropical Central and East Pacific andIndian Oceans. The subtropical West Pacific H500 signals lag 1-2 months those of SST anomalies inthe Central Pacific. the Variation of H500 LF component in the subtropical West and CenthelPaciflc become opposite in phase with the counterpart over the Northwest Paciflc, but the Hs500s QBsignals in this region have a slight tendency to propagate northward.The variation in phase of the low frequency oscillations, LF and QB, of SSTA in tropics andH500 in the Northem Hemisphere are closely related to annual cycles. As to the LF conshtuent forexample, most positit'e / negative extremes of SSIA in the tropical West Pacific are locked in fromJuly to August and from November to December, while the nagative/Positive extriemes of SSTA inthe tropical Central and Fast Pacitic and Indian Oceans are respechvely locked in the time laggingbehind from one to txo rnonths and two to three months to the appearance of extremes of SSTA inthe tropical West Pacific, as well as the associated negative / Positive extrcmes of H500 over thesubtropical Central and West Pacific appear in the time lagging behind from one to two months tothe appearance of extremes of SSTA in the tropical Central and East Pacific. However, the extremesof the QB constituent of the tropical SSTA and H500 are Iocked in relatively fixed months, forexamples, most posihxe/ negative extremes of SSTA in the tropical West Pacific are locked in fromJuly to August while those in the tropical Central and East Pacific and Indian Deeans are locked infrom September to October and from October to November, as well as most negative / positiveextremes of H500 are 1ocked in from November to DecemberSince both LF and QB conshtuents possess seasonal phase locking, a cedrin relahonship hasbeen found between these two kinds of low frequency oscillahons which plays an important role inthe happenings of El Ni1io, La Nifta and anomalous atmospheric general circulation.