两广地区夏季降水异常与澳大利亚东侧海温异常的联系及可能机制

摘要

The summer precipitation in Guangdong Province and Guangxi Zhuang Autonomous Region (hereafter GG region) with uneven temporal-spatial distribution has significant interannual variability.Using the observational station precipitation data,the marine and atmospheric reanalysis data,connections between precipitation(PGG) anomaly in GG region and sea surface temperature (SST) anomaly east of Australia during boreal summer in recent 40 years are investigated.Results show that P~ has a significant negative correlation with SST anomaly east of Australia on the interannual time scale.On the one hand,during the period of positive SST anomaly east of Australia,part of water vapor from the tropical central Pacific converges east of Australia,and another part of water vapor transfers to East Asia along the edge of western Pacific subtropical high.The anomalous moisture divergence is found over GG region.On the other hand,accompanied by the enhancement of convection east of Australia,the anomalous ascending is strengthened.Through the "Atmospheric Bridge" teleconnection,anomalous ascending is enhanced in the Maritime Continent,which strengthens the local Hadley circulation in East Asia and the anomalous descending in GG region.The water vapor transport and atmospheric circulation anomalies during the period of positive SST anomaly east of Australia are unfavorable to PGG,and vice versa.%广东省和广西壮族自治区(两广地区)夏季降水时空分布很不均匀,存在显著的年际变化.利用站点观测降水资料、海洋及大气再分析资料,研究了近40 a两广地区夏季降水年际异常与澳大利亚东侧海温异常的联系及机理.在年际时间尺度上,两广夏季降水异常与澳大利亚东侧的海温异常存在显著的负相关关系.当澳大利亚东侧海温异常偏高时,一方面,部分水汽由热带中太平洋向澳大利亚东侧海区辐合,部分沿西太平洋副热带高压边缘向东亚地区输送,两广地区为水汽辐散区域,另一方面,澳大利亚东侧海区的对流活动增强,该地区上空的上升运动异常增强,通过“大气桥”遥相关使得海洋性大陆地区的异常上升运动增强,从而加强了东亚地区的局地Hadley环流,使得两广地区下沉运动增强,二者共同作用致使两广地区夏季干旱少雨;反之亦然.