广西大范围暴雨气候异常对太平洋年代际涛动的响应

使用1961—2016年广西79个地面气象观测站逐日降水资料、美国国家海洋和大气管理局(NOAA)逐月太平洋年代际振荡(PDO)指数资料、NCEP/NCAR再分析资料、国家气候中心西太平洋副热带高压指数资料,利用相关和合成分析等方法研究广西大范围暴雨气候异常对PDO的响应。结果表明：广西大范围暴雨日数存在显著增多的突变新特征，对PDO有反位相变化的响应。当PDO处于冷位相时，对应着5—8月贝加尔湖阻塞高压和澳大利亚高压显著性偏强；索马里越赤道气流明显增强，与西太平洋副热带高压西侧边沿的东南风容易形成季风槽；形成从新几内亚岛东北部沿海到华南地区的低空风场为“反气旋-气旋-反气旋-气旋”波列传播，使广西大范围暴雨日数偏多。当PDO处于暖位相时，大气环流异常特征相反，广西大范围暴雨日数偏少。

RESPONSE OF GUANGXI LARGE-SCALE RAINSTORM ANOMALY TO PACIFIC DECADAL OSCILLATION

Using daily precipitation data from 79 surface meteorological stations in the Guangxi Zhuang Autonomous Region, NOAA Pacific Decadal Oscillation (PDO) index data, NCEP/NCAR reanalysis data, and NCC western Pacific subtropical high index data from 1961 to 2016, the present study adopts correlation and composite methods to investigate the response of the large-scale rainstorm anomaly in Guangxi to the PDO. The results show that the number of large-scale rainstorm days in Guangxi has significantly increased and its response to the PDO is reverse-phase change. When the PDO is in the cold phase, the Baikal obstruction high and the Australian high increase significantly from May to August; the cross-equatorial airflow in Somalia is significantly enhanced, and the southeast wind on the western edge of the western Pacific subtropical high is likely to form a monsoon trough. There is a wave train of "anticyclone-cyclone-anticyclone-cyclone"propagation in the low-altitude wind field from the northeastern coast of New Guinea to southern China, leading to the increase of large-scale rainstorm days in Guangxi. When the PDO is in the warm phase, the abnormal characteristics of atmospheric circulation are opposite, and there are fewer days of large-scale rainstorms in Guangxi.