The South China Sea Summer Monsoon Variation Characteristics And Its Relationship With Precipitation Of South China Under The Background Of Climate Warming

Using the1949-2011global grid NCEP daily average materials, Selecting the key zone of the South China Sea (10°N～20°N,110°E～120°E),when the average zonal wind steadily changes from east to west (west to east) and the same layer steadily has the Pseudo-equivalent temperature θse>335K (θse<335K)at850hPa to determine this pentad the SCSSM(South China Sea Summer Monsoon) onset date(retreat date),getting sequences of onset and retreat date nearly65years.Analysis shows that the onset date of the SCSSM is concentrated form the second pentad in May to the second pentad in June, and the mean onset date is the fifth pentad in May. The retreat date of the SCSSM is concentrated form the late September to the early October, and the mean retreat date is the first pentad of October. The onset date of the SCSSM has significant decadal variability, which is the most significant is16years cycle and3years cycle. The retreat date of the SCSSM has significant decadal variability too, which is the most significant is17years cycle and4years cycle.I found that clockwise vortex of the equatorial Indian Ocean region has similar guided influence to the cross-equatorial flow and the subtropical anticyclone on the outbreak (retreat)of the SCSSM. The onset of SCSSM is also related to the seasonal moving of the Hadley circulation and Walker circulation. Before the onset of SCSSM, the Hadley and the Walker circulation is complete, and following the breakout of SCSSM, both of them have a tendency to decrease, and after the retreat of SCSSM, both of them become back to their original state.The onset date of the SCSSM is closely related to its intensity, the summer monsoon onset later (earlier),its intensity is stronger (weaker),and the mutation of zonal wind changes earlier(later) in the upper troposphere than the lower. And the breakout of SCSSM is related to the precipitation of south China significantly, the summer monsoon onset early(late),the precipitation of south China is more than mean precipitation.Climate warming have an important influence on SCSSM, the onset date is more earlier, the retreat date is more later, the intensity is more weaker. In warm period, the early onset dates is more than those in cold period; the late retreat dates is more than those of cold period; years of stronger SCSSM is less than those in cold period; and the precipitation of south China is more than before, especially the southwest and the south part of China.