The characteristics of 30-60 day oscillation and its relation to the durative rainstorm in Guangdong

Using the NCEP/NCAR-2 reanalysis date and observed daily rainfall data in Guangdong during June of 2006, the characteristics of 30-60 day oscillation and its relation to the durative rainstorm over Guangdong were investigated. The results show that there exist no obvious 30-60 day oscillations of geopotential height and convection over Guangdong for the durative rainfall from 2 June to 5 June. However, the distinct westward propagation of low frequency geopotential height and northward propagation of low frequency geopotential height and convection occurred before the durative rainstorm from 18 June to 23 June. It is also found that the low pressure developing over western Pacific at the beginning of June may be the source of the local low frequency cyclone and convection. The northward movement of this low frequency cyclone and the development of the low frequency anticyclone over western Pacific afterward favor the maintenance of low frequency convergence trough over Guangdong and provide favorable circulation background for the durative rainstorm.