1978年酷暑与副高活动

THE SWELTERING SUMMER AND SUBTROPICAL HIGH IN 1978

摘要:

1978年长江中下游初夏出现空梅.盛夏连续干旱.并延续到9月上半月,以致6月下旬至9月上旬其间连续出现三段持续高温,为近百年来所未有。由于副热带高压的异常发展.500毫巴一个几乎围绕整个北半球的候平均副高环带不稳定崩解。在西太平洋形成一个强大的副高单体,逐候向西移动,增强和扩展。同时,伊朗～青藏高原有强暖高压东移.两个副高单体合并、增强并控制我国大陆,造成江淮流域7月上旬和9月上旬的两次特殊异常高温。低纬环流表明,副热带长波的异常发展也是造成1978年副高特强和酷暑的另一个原因。分析还发现,副高活动及持续高温有一个月左右的准周期性变化。

Abstract:

No Mai-yu rainfall was recorded over the middle-lower reaches of the Yangtze River in the early summer of 1978 and a spell of severe drought lasted from mid-summer to early September.Consequently, there occurred three periods of sustained high temperature from late June to early September which had never been observed in the past hundred years. This happened mainly due to the anomalous development of the subtropical high. A mean pentad subtropical high ring belt at 500 mb surrounding almost the whole northern hemisphere collapsed unstably and then an intense subtropical high cell which had formed over the west Pacific moved westward,intensified and extended pentad by pentad. At the same time, a powerful warm high moved eastward from the Iranian-Tibetan Plateaus. These two high centers then merged into One, intensified and dominated a great part of China, with exceptional high temperatures occurring twice over the Yangtze River reaches once in early July and the other in early September. The anomalous development of the subtropical long’wave systems was also responsible for the sweltering summer in 1978. Analysis indicates that there existed a quasiperiodic change for about one month in the subtropical high and sustained high temperature.