2005年6月我国南方雨带异常偏南的分析

Analysis of Rainband Anomaly in the Southern China in June 2005

2005年6月我国南方雨带异常偏南。利用逐日观测资料、NCEP再分析资料以及NOAA-OLR资料对该年6月的天气形势特征和一些主要影响天气系统进行了诊断分析。讨论了西太平洋副热带高压、低层冷空气和水汽输送等与雨带异常之间的关系。结果表明西太平洋ITCZ偏弱,热带气旋少,使西太平洋副热带高压主体长时间偏南。青藏高原南部和低纬洋面上的对流异常,影响该地区季风环流,造成水汽向低纬地区集中,西南季风水汽输送带异常偏南。高层中高纬度异常环流,抑制南亚高压东段脊线北抬,高层西风异常通过动量下传,加强中低层西风锋区,冷空气南下到偏南地区等均是造成雨带异常偏南之原因。

Based on NCEP reanalysis, data and OLR data from NOAA, the characteristics and the causes for the rainband anomaly over the southern China in June 2003 are studied. The results show that exceptional weak ITCZ over the West Pacific Ocean and the fewer tropical cyclones make subtropical high continually stay in the south area; the monsoon circulation is influenced by the convective anomaly over the southern Tibetan Plateau and the low-latitude ocean, thus the moisture is concentrated to the low-latitude area and the southwest monsoon moisture transfer passage is to the south of its normal location; the ridge line of the south Asian high is prevented by the middle and high latitude circulation anomalies at high levels from moving northward, moreover, the west wind front at lower levels is intensified by west wind anomalies at high level through momentum downward transfer. All the facts mentioned above give the reasons for the rainband anomaly.