南海周边越赤道气流的多时间尺度变化特征及其与环流和降水的联系

利用NCAR/NCEP-1再分析资料、NOAA的OLR资料以及GPCP降水资料等，通过功率谱分析、超前滞后回归等方法，对夏季南海周边105 °E、125 °E以及150 °E三支越赤道气流进行了多尺度特征分析，重点探讨三支越赤道气流季节内振荡与热带大气环流异常及南海周边降水的联系。结果表明，在季节内时间尺度上，105 °E与125 °E越赤道气流均具有10~20 d以及30~60 d低频振荡显著周期，而150 °E越赤道气流则以10~20 d周期为主。在年际尺度上，105 °E、125 °E、150 °E越赤道气流分别具有2~4年、2~3年、2~6年振荡周期。无论是季内还是年际变化，皆以105 °E与125 °E这两支越赤道气流之间关系较密切。南亚-南海-西太平洋地区对流层低层10~20 d振荡的气旋(对流加强)和反气旋(对流减弱)的环流活动变化，决定着105 °E及125 °E越赤道气流的10~20 d振荡的演变。这两支越赤道气流之30~60 d振荡所伴随的异常变化与热带夏季季节内振荡(BSISO)的演变过程非常相似，而150 °E越赤道气流之30~60 d振荡所伴随的异常低频环流则与南半球热带辐合带关系密切。105 °E及125 °E越赤道气流的季节内振荡及年际异常均与南海周边降水异常密切相关。 

MULTI-SCALE CHARACTERISTICS OF THE CROSS-EQUATORIAL FLOWS AROUND THE SOUTH CHINA SEA AND ITS RELATIONS WITH CIRCULATION AND PRECIPITATION

Multi-scale characteristic analysis of the three cross-equatorial flows at 105 °E, 125 °E and 150 °E around the South China Sea in summer was carried out, and the relationships among the intra-seasonal oscillations of the three cross-equatorial flows and the tropical atmospheric circulation anomalies and precipitation around the South China Sea are discussed by power spectrum analysis, lead-lag regression and other methods, based on the NCAR/NCEP-1 reanalysis data, NOAA''s OLR data, and GPCP precipitation data, etc. The results show that the 105 °E and 125 °E cross-equatorial flows have significant periods of 10~20 d and 30~60 d low-frequency oscillations on the subseasonal scale, while the 150 °E cross-equatorial flow is dominated by 10~20 d periods. On the interannual scale, the 105 °E, 125 °E and 150 °E cross-equatorial flows have oscillation periods of 2~4 years, 2~3 years, and 2~6 years, respectively. The relationship between 105 °E and 125 °E cross-equatorial flow is very close in both intraseasonal and interannual time scale. A pair of cyclone (convection enhancement) and anticyclone (convection weakening) circulation with 10~20 d oscillating at low troposphere in the South Asia-South China Sea-West Pacific region determines the 10~20 d oscillation of the evolution of 105 °E and 125 °E cross-equatorial flows. The anomalous variation associated with the 30~60 d oscillations of the above two cross-equatorial flows are very similar to the evolution of the tropical summer seasonal oscillations (BSISO), while the anomalous low-frequency circulation accompanied by the 30~60 d oscillation of the 150 °E cross-equatorial flow is closely related to the tropical convergence zone in the southern hemisphere. The intraseasonal oscillations and interannual anomalies of the 105 °E and 125 °E cross-equatorial flows are significantly correlated with precipitation anomalies around the South China Sea.