南海夏季风爆发的数值预报模拟实验

摘要

1998年5月21日00时（UTC），对流层上部200 hPa的南亚反气旋中心位于（16oN，94oE）附近，850 hPa南海的中南部仍为副热带反气旋控制；到21日12时，200 hPa的南亚反气旋中心迅速移到（21oN，94oE）附近，同时850 hPa的南海副热带反气旋减弱东撤，南海的中南部由东南风转变为西南风，南海夏季风爆发。本文利用美国国家大气研究中心和宾西法尼亚州大学联合研制的中尺度模式（MM5V2）模拟预报这一过程，同时通过敏感性实验研究了区域边界条件和水平分辨率对季风预报模拟实验的影响。%Based on NCEP/NCAR daily reanalyzed data, on 0000 UTC 21 May in 1998, at 850 hPa the Western Pacific subtropical high ridge (WPSHR) was just over the South China Sea Region (SCS). In the upper troposphere (200 hPa), the center of subtropical anticyclone located near (16oN, 94oE). By 1200 UTC the WPSHR retreated suddenly eastward from SCS and weakened. On the meantime, in the lower troposphere (850 hPa) in the SCS the southeasterly vanished and the southwesterly prevailed, i.e. the SCS summer monsoon onset happened. In the upper troposphere (200 hPa) the subtropical anticyclone, being an important characteristic of SCS summer monsoon onset, shifted abruptly northward to the northern Indo-China Peninsula (21oN, 94oE). Using the NCEP/NCAR reanalyzed data and NCAR/PENN MM5V2 model, some numerical experiments about the summer monsoon onset in SCS had been performed. The control experiment is capable of reproducing above-mentioned summer monsoon onset process in SCS. The results of sensitivity experiments show: (1) The lateral boundary conditions have an important influence on the monsoon onset time in SCS. (2) Using lower model horizontal resolution (108 km), the model can produce better large-scale monsoon circulation features than that using higher resolution (36 km).