中国东部夏季降水准两年振荡的主振荡型分析

利用中国160个测站月降水资料和NCEP/NCAR再分析月平均资料,选取中国东部夏季降水准两年振荡(TBO)分量做主振荡型分析(POP)和伴随相关分析(ACP)。结果表明:第一个POP对占东部夏季降水TBO总方差的18.2%,循环周期约为4年。实部为过渡型,振幅在1950年代中期和1980年代初期明显增大,在1980年代中后期到1990年代中期振幅的TBO特征异常显著。虚部为峰值型,在华南东部—长江流域—江淮流域有大范围的正值中心,高值中心位于长江—江淮流域,华南中西部为一负中心。虚部型振幅,1990年代中后期虚部型的振幅有明显加强。海温的伴随相关说明东部夏季降水TBO过渡型与西太平洋海温异常相对应,峰值型与赤道中东太平洋海温异常相对应。850 hPa风场异常、赤道纬向风异常和经向垂直环流异常的伴随相关显示,当POP对处于过渡型(负过渡型)时西太平洋对流旺盛(弱),南海上空有反气旋(气旋)生成。当POP对处于峰值型(负峰值型)时,赤道上Walker环流减弱(加强),经向上Hardly环流位置偏南(北),强度加强(减弱)。总之,中东太平洋海温异常与东部夏季降水TBO的传播有着密切联系,并通过海气相互作用和低纬与中高纬的相互作用来影响中国东部夏季降水TBO的传播,南北半球环流的相互作用也需要进一步探讨。

Principal Oscillation Pattern of QBO in Summer Precipitation of East China

Using the mean monthly rainfall data at 160 stations in China and NCEP/NCAR reanalysis mean monthly data,the quasi-biennial oscillation(QBO) in summer rainfall of East China is studied by Principal Oscillation Pattern(POP) and Associated Correlated Pattern(ACP) analyses.The POP analysis shows that the first POP represents 18.2% of the variance of the time series with a period about 4 years.The real part of the first POP is a transitional model with significant increscent amplitude in middle of 1950s and early period of 1990s.The QBO feature of the amplitude is remarkable between the mid-late period of 1980s and middle 1990s.The imaginary part of the first POP is a peak model.The positive value covers the east of South China,Yangtze River valley and Yangtze River-Huaihe valley with a higher value center in Yangtze River-Huaihe valley and a lower value center in middle-west of South China.The amplitude of the peak model has noticeable enhanced in mid-late period of 1990s.The transitional model is correspond to anomaly of west Pacific sea surface temperature(SST) while the peak model is to that of the equator central and east Pacific SST through ACP analysis of SST.The associated correlations of 850 hPa wind,equator zonal wind and meridional wind denote that,when the model of summer rainfall QBO in East China is in the transitional state(negative),the convective is stronger(weaker) over west Pacific and anti-cyclone(cyclone) geneses over the South China Sea,while the model is in the peak state(negative),the equatorial Walk cycle is weaker(stronger) and the location of Hardly cycle is further south(north) with the strengthened(weakened) intensity.Anyway,the SST anomaly in middle and east Pacific has close relationship with summer rainfall QBO propagation in East China by ocean-atmosphere interaction and low-middle-high latitude interaction,and the interaction between Southern and Northern Hemisphere circulation needs more study.