江淮下游汛期降水与ENSO冷暖事件的关系——以里下河腹部地区为例

应用综合Niño指数,分析了江淮下游里下河腹部地区1957-2006年间汛期降水与ENSO冷暖事件的关系及环流形势。结果显示:汛期降水与ENSO冷暖事件的遥相关具有较为显著的阶段性特征。El Niño、La Nina的翌年汛期降水分别以负、正距平偏多,汛期降水的正负距平转换出现在1970年代末左右。汛期降水与Niño指数具有2-7 a左右的相似周期,且二者在1980年前后出现了明显的相位转换。El Niño翌年汛期降水为正距平的环流场显示,东亚环流经向呈“+、-、+”高度距平配置,且副高范围扩大,偏西偏北,存在典型的梅雨锋面,雨带停留在江淮下游地区,利于降水形成。而La Nina翌年汛期降水为正距平的环流场表明,副高位置偏东偏北收缩,东亚经向环流呈“-、-”位势高度距平,低、中层分别为西南风、偏东南风距平,缺少梅雨锋面,汛期降水偏多的程度较小。

Relationship between precipitation in flood season and ENSO warm and cold events in the lower reaches of Jianghuai Basin: A case study in the Inner Lixiahe Region

Niño index is applied to detect the relationships between Precipitation in Flood Season(PFS)and ENSO events in the inner Lixiahe region of the lower reaches of Jianghuai basin from 1957 to 2006.Results show that a nice teleconnection effect can be detected between PFS and Niño index,which reveals that precipitation anomalies tend to be positive(negative)in the year after the warm El Niño event(cold La Nina event),and there is a significant stage change for precipitation anomalies in the late 1970s and the early 1980. Also,wavelet period analysis for the PFS and the Niño index indicates that a similar period can be found in both PFS and the Niño index in a period of 2-7 years,and the wavelet coherence analysis shows a significant phase switch around 1980 as a result of the teleconnection of the sea surface temperature anomalies.Furthermore,the atmospheric circulation configuration for the ENSO events is described.For the El Niño warm events,its specific atmospheric circulation configuration can be concluded that the east Asia meridian circulation appears to be a"+,-,+"geopotential height anomaly,and the west Pacific subtropical high position is located closer to the west and the north,southwest winds prevail in the middle and lower troposphere,and there is an obvious plum rain frontal surface in the lower Jianghuai region which is beneficial for the staying of the plum rain belt,thus the staying of the plum rain belt might result in more precipitation.However,in contrast to atmospheric circulation configuration of the El Niño warm events,the specific atmospheric circulation configuration for the La Nina cold events may be summarized that the west Pacific subtropical high position tends to shrink back to the east and the north,the east Asia meridian circulation appears to be a"-,-"geopotential height anomaly,southwest winds prevail in the lower troposphere and southeast wind in the lower and middle troposphere respectively.Therefore,there is no obvious plum rain frontal surface under this specific atmospheric circulation configuration,hence there are less positive precipitation anomalies in the lower reaches of north Jianghuai basin.