El Nio事件次年中国东部夏季气温分布特征研究

Study on the characteristics of air temperature in summer following El Nio events over East China

利用Had ISST和NCEP/NCAR再分析资料,采用统计学方法分析了1949年以来El Nio事件次年夏季中国东部气温分布特征。结果表明,混合型El Nio次年夏季,中国东部气温距平表现为山东—淮河流域及华南沿海出现负距平,其余地区为正距平;东部型,则表现为中国东部地区整体的负距平气温,且北方降温幅度明显大于长江以南地区;中部型,主要表现为长江以北气温负距平远大于长江以南。结合环流形势分析发现,三类El Nio事件次年夏季的赤道地区(5°S^5°N)异常纬向垂直环流均表现为三圈型,但3类异常Walker环流不仅强度有差异,纬向范围也有所不同。500 h Pa上西太平洋副高的强度和范围,是造成三类El Nio事件次年夏季中国东部地区气温距平分布差异的主要原因之一,850 h Pa上西南暖湿气流的输送对其也存在明显影响。

Using the Had ISST and NCEP/ NCAR reanalysis data,a diagnosis and analysis was carried out for the abnormal temperature over eastern China（ EC） during El Nino events in the following summer beginning from 1949.The results showthat,in the summer after EP ＋ CP El Nino,the negative temperature anomaly appeared in the Shandong-Huaihe Basin and along the coast of southern China,while the other areas showed positive anomaly.The EP El Nino,EC showed negative anomaly throughout,and the range in the north was greater than that to the south of the Yangtze River. For the CP El Nino,the temperature throughout the north was down more than that in the south of the Yangtze River. The corresponding atmospheric circulation analyses indicated that,in the summer after the three types of El Nino events,the anomalous zonal vertical circulation of the equatorial region（ 5°S—5°N） was shown to appear as three circles,but their anomolies not only had differences in strength,the latitude ranges were also different. In the summer after EP ＋ CP El Nino events or EP El Nino events,there were two abnormal Walker circulations in the equatorial Pacific,while in the summer following CP El Nino events there were two Walker circulation anomalies in the equatorial India Ocean. The intensity and range of the subtropical high in the Western Pacific Ocean at 500 h Pa was one of the main reasons for the difference of temperature distribution in EC during the summer after the three types of El Nino events. In the summer following EP ＋ CP El Nino events,the 500 h Pa geopotential height anomaly showed ＂sandwich＂type distribution over eastern China. The eastern part of northeast China,the Shandong Peninsula and southern China area were positive anomalies,while the other regions were reduced to some extent,and the negative anomaly amplitude decreased from north to south. In the summer after EP El Nino events,the 500 h Pa geopotential height had different degrees of reduction over EC,the meridional circulation was strengthened,which was conducive to the cold air travelling southward,thus the temperature was significantly lower than normal,the intensity of the subtropical high in the Western Pacific was weakened,its coverage decreased,and there was a certain degree of negative temperature anomaly in southern China. In the summer after CP El Nino events,the meridional circulation was relatively strong at the 500 h Pa geopotential height over EC,which was conducive to the cold air travelling southward to the north of the Yangtze River region,the temperature was lowin the north,the West Pacific subtropical high travelled southward,with a rather flat shape,the effect range of the subtropical high increased and its strength increased slightly,and the effect of the subtropical high on southern China strengthened,so that the temperature in southern China increased.However,the effect of the subtropical high to the north of the Yangtze River weakened and caused the temperature there to drop; the transportation of the southwest warm and humid air at 850 h Pa also had a significant effect on this.