2005年南海夏季风建立偏晚和持续异常偏南的成因分析

通过分析大气环流及其热力结构演变特征，揭示2005年春末夏初南海季风爆发偏迟和持续异常偏南的原因。结果表明，阿拉伯高压偏强，与中高纬度高压脊叠加，导致较高纬度冷空气南下青藏高原南侧及中南半岛一带，抑制了中南半岛附近地区大气增温，不利于南海季风的爆发；索马里急流及赤道西风建立偏晚使中南半岛对流凝结潜热偏弱，是中南半岛一带大气增温偏迟的另一重要原因。6月上中旬，印度半岛北部冷空气势力偏强，大气增温缓慢，使印度季风和亚洲南部季风槽向北推进迟缓，使强劲的西南季风径直向东输送进入南海，有利于南海西南季风长期持续偏南。春末青藏高原积雪偏多，积雪融化抑制了地面增温和大气感热加热，是南海季风爆发偏晚的另一重要原因。6月上中旬，西南季风北上偏迟导致高原对流偏弱，热源偏弱，负反馈作用抑制了西南季风进一步北上，导致西南季风持续异常偏南。

REASONS FOR THE LATER ONSET OF SOUTH CHINA SEA SUMMER MONSOON (SCSM) AND ITS ANOMALOUS SOUTHWARD PERSISTENCE IN 2005

Atmospheric circulation and heat structures are discussed to reveal the reasons for the later onset of South China Sea Summer Monsoon(SCSSM) and its southward persistence in 2005.The results show that a stronger Arabian High and an overlapped ridge in the middle and high longitude guided colder air to India Peninsula and Bay of Bengal as well as the northern part of Indo-china Peninsula,which delayed the heating of the atmosphere and the outbreak of SCSSM.Somali Jet and cross-equatorial southerly winds in t...