赤道地区向西传播的40天周期低频波

本文用滤波和EOF位相合成技术对1981年7—12月份赤道地区出现的向西传播的40天周期低频波进行了分析。结果认为东太平洋地区从南半球到北半球的越赤道40天周期温度波是产生这种西传波的主要原因。这种波动主要产生于两个源地:一个是赤道150°E附近的对流层下层;另一个是110°W的赤道对流层上层。这两处产生的低频波性质不一样,前者与对流密切相关。通过计算整层积分的非绝热加热Q_1和水汽汇Q_2,结果表明Q_1加热中心在东太平洋也有越赤道传播。在150°E以西Q_2加热中心是向西北传播的,与低频波方向一致,Q_1的传播特征不明显,这说明西太平洋地区的热带对流可能有这种周期振荡。

WESTWARD PROPAGATION OF 40-DAY LOW-FREQUENCY OSCILLATION OVER THE EQUATORIAL REGION

The characteristic features of westward propagating 40-day low-frequency oscillations over the equatorial region during the period of July-December 1981 are analyzed by using the band-pass filter and EOF composite technique. The results show that the crosequatorial 40-day temperature waves over the eastern Pacific are mainly responsible for the formation of the westward propagating modes. There are two main sources for these modes. The one is in the vicinity of 1500E at equator. The other is in the vicinity of 110°W at equator. The lowfrequency disturbances formed in these two places are different from each other.The results of vertically integrated heat source Q₁ and moisture Q₂ show that the Q₁ heating centres propagate across the equator over eastern Pacific, which is in good agreement with the propagation of the cross-equatorial temperature waves. The Q₂ heating centres seem to originate from around 150°E at equator and move northwestward.