大气季节内振荡的活动与El Nino

ACTIVITY OF ATMOSPHERIC INTRASEASONAL OSCILLATION AND EL NINO

对三次ＥｌＮｉｎｏ发生前后的ＥＣＭＷＦ资料用滤波方法（带通，低通）进行分析，得到的结果清楚地表明，在ＥｌＮｉｎｏ发生前热带季节内振荡较强，而伴随ＥｌＮｉｎｏ发生，季节内振荡明显减弱，这种能量变化最明显的地区是赤道东太平洋地区；对于周期在９０天以上的热带准定常波，伴随ＥｌＮｉｎｏ的发生其能量明显增加，这种增加反映最显著的区域是从大西洋往西一直到西太平洋。对中纬度（２５－３５°Ｎ）及中高纬度（４０－５０°Ｎ）地区的准定常波能量分析表明，中纬度地区的准定常波能量比低纬大，准定常波能量变化在中纬度（２５－３５°Ｎ）表现出与低纬能量变化一致的情形，即伴随着ＥｌＮｉｎｏ的发生，准定常波能量增加；中高纬度（４０－５０°Ｎ）只在亚洲大陆（１００－１７０°Ｅ）表现出与热带一致的能量变化。结果还显示，热带季节内振荡在低层的东传对赤道西风异常及对ＥｌＮｉｎｏ的发生、发展起着很重要的作用。

? Three El Nino events are analyzed based on filter method(band pass,low pass)by using ECMWF data.It is clearly shown that tropical intraseasonal oscillation is strong prior to El Nino, corresponding to the occurrence of El Nino event,intraseasonal oscillations obviously weaken and the most obvious variation zone is in tthe tropical eastern Pacific .For quasistationary wave (with period greater than 90 days),corresponding to the occurrence of El Nino event,its kinetic energy increases obviously and the most obvious variation zone is from Atlantic westward to the tropical western Pacific.The quasistationary wave kinetic energy is greater in middle(25-35°N)and middlehigh(40-50°N)latitude than in the tropics.The quasistationary wave kinetic energy in middle latitude show consistent variation with tropical quasistationary wave energy variation,that is,corresponding to the occurrence of El Nino event,quasistationary wave kinetic energy increases in middle latitude.In middlehigh latitude(40-50°N),quasistationary wave shows consistent variation with the tropics in Asia continent(100-170°E).We also point out the eastward propagation of tropical intraseasonal oscillation plays an important role to tropical westerly anomaly and occurrence of El Nino.