中高纬环流对1998年7月西太平洋副热带高压短期变化的影响机制

针对1998年7月长江中下游地区二度梅期间副热带高压的短期演变特征,利用NCEP逐日资料,首先揭示了此期间西太平洋副热带高压发生东西断裂、副高单体发展的短期异常特征,进而指出了中高纬环流调整与副高短期变异的对应关系.在发现与中高纬环流调整相伴随的强冷空气是副高发生变异的关键因素的基础上,利用大气热力学基本原理,研究副高短期变异的动力机制,发现在副高边缘的冷暖空气活动通过与南北风发展直接关联,而影响副高的短期变异,是副高短期变异的重要机制之一.最后,利用R42L9/LASG IAP大气环流模式,通过敏感性数值试验证实了上述冷暖空气活动影响副高发生变异的动力机制.

On the Short-Term Variation of Subtropical Anticyclone over the Western Pacific Affected by the Mid-High Latitudes Circulation in July 1998

The daily NCEP/NCAR reanalysis data are employed to study the short term evolution of the subtropical anticyclone over the western Pacific(SAWP) in July 1998 Firstly, the characteristics of SAWP related to the three distinct periods of Meiyu are analyzed It is found that the breaking of the belt type SAWP is closely related to the variation of the circulation in the mid high latitudes Specifically, the intrusion of cold air from the mid high latitudes into the subtropics is very important to the breaking of the belt of SAWP Then the dynamic processes related to the short term variation of SAWP are studied based on the general thermodynamic theory It is shown that the southward/northward intrusion of cold/warm air contributes to the development of north/south wind around SAWP, and result in the SAWP anomalies At last, this mechanism is verified by a numerical experiment based on the atmospheric circulation model R42L9/LASG IAP