Low Frequency Oscillations of Southern Hemispheric Critical Systems and Precipitation During Flood Season in South China

By using daily precipitation data over South China and the NCEP/NCAR daily mean reanalysis data of SLP in Southern Hemisphere during 1960—2008, the low frequency oscillations of Southern Hemispheric critical systems and precipitation during raining seasons in South China are investigated by means of statistical method, for example, MTM-SVD, and so on. The LFV spectrum results show a 30—60 days low frequency oscillation and variation of 5—7 days for the precipitation during raining seasons in South China. Australian high in Southern Hemisphere can also be decomposed into 30—60 days low frequency oscillations, 10—20 days bi-weekly oscillations and variations of 5—7 days and 2—3 days. Mascarene high has 30—90 days low frequency oscillations and characteristics of bi-weekly oscillations. The MTM-SVD method can identify coupled spatial and temporal evolving signal by using both phase and amplitude information. Tracking the spatial and temporal coupling evolution of low-frequency oscillation with 30—60 days, it is found that the Mascarene and Australian high from strong to weak is corresponding to the rainy zone transfer from southwest to northeast in South China, and vice versa. South rain belt of precipitation in South China coincides with the variations and phase of the Mascarene and Australian high very well, but North rain belt is opposite with the Mascarene and Australian high. When the SLP of Mascarene and Australian high are positive from the usual, southern rain belt in South China is usually strong and northern rain belt tends to by weak, and vice versa.