中国东北夏季极端高温变化特征及其与环流异常的联系

利用东北地区1960—2010年夏季逐日气温资料,研究了中国东北地区夏季极端高温的时空变化特征和区域性特征,并对东北地区夏季极端高温事件与大气环流异常的可能联系进行分析。结果表明,东北地区夏季极端高温频数有明显的升高趋势,升高幅度由南向北逐渐增大;东北地区南部、东北部和西北部夏季极端高温频数的年际及年代际变化存在明显差异。东北地区夏季极端高温高发年500 hPa位势高度上盛行纬向环流,东北地区上空位势高度的垂直分布接近于正压结构,且一直延伸至对流层顶,海平面气压场上亚洲大陆低压明显偏弱,南北气压梯度减小,冷空气不易南下;低发年,则反之。

VARIATION FEATURES OF SUMMER EXTREME HIGH TEMPERATURE OVER NORTHEAST CHINA AND ITS RELATIONS WITH ATMOSPHERIC CIRCULATION ANOMALY

Based on the 1960--2010 summer daily temperature data in Northeast China, the spatial and temporal features and regional variation trends of the extreme high temperature are studied, and the possible linkages between summer extreme high temperature events over Northeast China and atmospheric circulation anomalies are analyzed. The results show that the frequency of extreme high temperature obviously increases all over Northeast China, the increasing range gradually rises from south to north. The interannual and interdecadal changes in the regions of south of Northeast China, Northwest China and Northeast China are obviously different. During the high frequency years of extreme high temperature, the zonal circulation prevails at 500 hPa, the vertical distribution of geopotential height over Northeast China presents quasi-barotropic structure. Asian continental low at sea level pressure field is obviously weak, and north-south pressure gradient decreases, which cause the cold air to affect Northeast China difficultly. During the low frequency years, there are converse conditions.