THE STRONG DRAGON BOAT RACE PRECIPITATION OF GUANGDONG IN 2008 AND QUASI-10-DAY OSCILLATION

Guangdong suffered from the most serious precipitation of its corresponding time during the dragon-boat race of 2008 since 1951. The relationship between the strong dragon-boat precipitation in 2008 and atmospheric low-frequency oscillation was analyzed with the methods of wavelet analysis, correlation and Lanczos filter. Results showed that the daily rainfall exhibits a significant 7 to 12-day quasi-periodic oscillation (namely quasi-10-day oscillation) during the precipitation, the daily 500 hPa height over Guangdong exhibits a significant 8 to 13-day quasi-periodic oscillation, and the daily 850 hPa zonal wind averaged over the north of the South China Sea presents a significant quasi-12-day periodic oscillation. The Guangdong rainfall during the annually first rainy season is most closely correlated with monsoon over the north of South China Sea, and less closely with an upper-level trough at 500 hPa affecting Guangdong. Strong monsoon surges induced two heavy rainfall processes in 2008. The monsoon surges joined with a westward-propagating quasi-10-day oscillation that originated from the central Pacific and was enhanced in a strong convective region east of the Philippines and a northward-propagating monsoon that originated from the southern South China Sea was enhanced. With composite analysis of typical phases, the common evolution characteristics of atmospheric circulation of the two heavy rainfall processes were analyzed for different phases. These features can be used as reference for medium prediction of heavy rainfall processes in Guangdong.