THE DECADAL VARIATION OF QUASI-BIWEEKLY AND 20 ~60-DAY INTRASEASONAL OSCILLATION IN SOUTH CHINA SEA IN SUMMER(MAY-OCTOBER)
LI Chun-hui
HE Chao
ZHENG Bin
GU De-jun
LIN Ai-lan
Abstract：Using period and wave number-frequency analysis,the sub-seasonal variability of summer (May—October)convection over the South China Sea exhibits two dominant timescales,one with a quasi-biweekly (QBWO)period (1 0 ~20 days)and the other with an intraseasonal oscillation.The northward propagation spectrum is much stronger than the southward,meridional propagating QBWO and ISO with wave number 2.In the zonal propagation,for the QBWO mode,the westward propagation spectrum with wave number 1 is the strongest.But for the ISO,the spectrums of the westward propagation and eastward propagation with wave num-ber 1 are quite the same.During three different time of the atmospheric circulation of the decadal change, namely 1 958—1 976、1 977—1 993 and 1 994—201 1 ,the QBWO intensity,propagation numbers,frequency and spectrum energy tend to enhance gradually.Different from the QBWO mode,the intensity of ISO experiences periods of being normal and slightly weaker,weaker and stronger variation,while the propagation numbers,fre-quency and spectrum energy are the stronger,weaker and stronger.The factors that cause these changes are dif-ferent.The air-sea interaction and the water vapor convection conditions played a leading role together in the change of QBWO.For the ISO mode,vertical zonal wind shear is more important.
Keywords：South China Seaquasi-biweekly20 ~60-daydecadal oscillation
Publication Date：2016-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：11( 577-587 )