中国东部夏季分区降水对海温异常响应特征的研究

Analysis on response of regional summer rainfall in East China to SST anomaly

用刘征宇最新发展的广义平衡反馈方法结合经验正交分析和旋转经验正交分析法,研究中国东部6个分区夏季降水异常对各海盆海温异常(SSTA)模态的响应特征,探讨了东北区降水异常对SSTA的响应机制。结果表明:各分区降水异常对SSTA的响应特征有明显差异。东北区降水异常对热带太平洋SSTA的回应显著,当SSTA表现为类似El Nio模时,该区夏季降水增加;江淮区降水异常同时受到中纬度以及热带SSTA的强迫,对热带太平洋SSTA的类似La Nia Modoki模、北大西洋SSTA三极型模等回应显著;西南地区的降水异常主要与中纬度SSTA有密切关联。对流层高度场对热带太平洋SSTA类似El Nio模的直接回应在热带太平洋上空为显著正异常。通过东亚—太平洋型遥相关波列使东北地区上空高度场出现负异常,并在其西侧形成负异常中心,对流层低层为气旋性环流异常。这一环流回应与东北地区夏季降水偏多时的环流特征相近。

A method of combining generalized equilibrium feedback assessment developed lately by Liu with Empirical Orthogonal Analysis and Rotated Empirical Orthogonal Analysis is applied to examine the response characteristics of summer precipitation anomaly in six East China climatic regions to sea sur- face temperature anomaly（SSTA） mode over five basins and to discuss the response mechanism of precip- itation anomaly over the Northeast region to SSTA in tropical Pacific. Results show that the response char- acteristics of anomalous precipitation anomaly over different areas to SSTA are obviously different. In the Northwest region, the precipitation anomaly has a predominant response to the tropical Pacific SSTA, which expresses that when the SSTA pattern is similar to the El Nino mode, the precipitation in summer will increase. In Jianghuai region, the precipitation is robust and is forced by mid-latitude and tropical SSTA, so it has an obvious response to La Nina Modoki mode over the tropical Pacific SSTA and a tripole mode over the North Atlantic SSTA. In addition, the precipitation anomaly over the Southwest region has a close relationship with mid-latitude SSTA. The direct response of geopotential height field in tropo- sphere to similar El Nino mode over the tropic Pacific SSTA is positive anomaly at the tropospheric upper level over the tropic Pacific, and a negative anomaly of upper level geopotential height over the Northeast region occurrs through the East Asia-Pacific （EAP） wave train teleconnection with an anomalous center in the west of the area and a cyclonic circulation anomaly in the low level troposphere. This circulation re- sponse is similar to that when the rainfall in Northeast region is above normal.