1948~2004年全球越赤道气流气候变化
THE CLIMATOLOGICAL VARIATION OF GLOBAL CROSS-EQUATORIAL FLOW FOR THE PERIOD OF 1948~2004
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摘要: 利用1948年1月~2004年12月逐月NCEP/NCAR的全球1000hPa、850hPa、700hPa、600hPa、500hPa、400hPa、300hPa、200hPa、150hPa、100hPa的10层经向格点风,计算了全球越赤道气流和年变化,分析了全球850hPa越赤道气流通道的时、空变化特征。指出在研究的时间段内,全球850hPa越赤道气流有明显的长期趋势变化和年代际变化。近57年,6~8月的45~50°E、5~9月的105~115°E、5~9月和5~11月的130~140°E、2~4月的20~25°E的越赤道气流有明显的加强,6~8月的50~35°W的越赤道气流减弱。夏季索马里的越赤道气流,平均每10年增强0.25m/s,而130~140°E,5~9月的越赤道气流,平均每10年增强0.32m/s。奇异谱分析表明,850hPa越赤道气流的年代际变化和趋势变化的方差贡献达到35%~45%。年际变化的方差贡献不超过30%,还指出夏季太平洋的越赤道气流的强度变化与南方涛动有明显关系,弱南方涛动时,有强的越赤道气流。而索马里急流强度与北大西洋涛动有弱的正相关。Abstract: By using monthly NCEP/NCAR meridional gridpoint wind data at the levels of 1000,850,700,600,500,400,300,200,150 and 100hPa from 1948 to 2004,the intensity of global cross-equatorial flow is calculated.The spatial and temporal variation of global cross-equatorial flows at the 850hPa level are shown and discussed.The results show that the strength of the 850hPa global cross-equatorial flows represent obviously long-term variation and interdecadal change during the period.Evidence suggests that the cross-equatorial flow of the passages at 45~50°E in June to August,105~115°E in May to September,130~140°E in May to September and May to November and 20~25°E in February to April intensified and that the cross-equatorial flow of the passages at 50~35°W in June to August weaken in the past 57 years,with an increase of 0.25m/s/10a for summer Somali cross-equatorial flow and increase of 0.32 m/s/10a for cross-equatorial flow at 130~140°E in May to September.The results of Singular Spectrums Analysis(SSA) for the time series of cross-equatorial flow indicate that for the cross-equatorial flow at 850 hPa,the interdecadal and long-term trend changes have 35%~45%,and the interannual variation has no more than 30%,in variance contribution.The results also reveal that the interannual variation of intensity of the cross-equatorial flow in summer in the Pacific has significantly correlated with Southern Oscillation.With weak Southern Oscillation,strong Cross-equatorial flow in Pacific will happen.But summer Somali Jet only has little positive correlation with NAO.
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