THE NORTH-SOUTH ANTI-PHASE DISTRIBUTION OF RAINFALL IN MEIYU PERIODS AND ITS RELATIONSHIP WITH QUASI-BIWEEKLY OSCILLATION IN THE ATMOSPHERE

Based on the daily rainfall datasets from 740 stations in China from 1954 to 2005 and the NCEP/NCAR reanalysis data, the relationship between the north-south anti-phase distribution (APD) of rainfall during Meiyu periods and the Quasi-Biweekly Oscillation (QBWO) in the atmosphere was analyzed. Diagnostic results are as follows: (1) there was significant north-south oscillation of Meiyu rainfall during the 16 years from 1954 to 2005. Since the 1990s, the APD enhanced significantly and showed 2- and 4-6-year period. In the region with more rainfall, the QBWO was always more active. (2) The APD of Meiyu and north-south movements of precipitation in eastern China belong to the same phase. (3) The 10-25 day filtered water vapor flux could spread to the area north of 30°N in 1991. The divergence of the water vapor flux which propagated from middle- and higher- latitudes to the of Yangtze-Huaihe River Basins (YHRB) was significant in 1991, but the latitudes that the water vapor flux could reach were further southward and there was no southward propagation of divergence in 1993. (4) The locations of Western Pacific Subtropical High (WPSH) and 10-25 day anti-cyclone, which modulated WPSH’s advancement in and out of the South China Sea, were relatively northward in 1991. Furthermore, the vertical circulation showed north-south deviation between 1991 and 1993, just as other elements of the circulation did.