南海夏季风监测预测研究与业务现状评述

Monitoring and Forecasting for the Onset of South China Sea Summer Monsoon

南海夏季风是影响中国降水的重要系统,它的爆发预示着东亚夏季环流的发展。南海夏季风爆发前后的大气环流有明显的变化,包括西太平洋副热带高压撤出南海,南海地区低层西南风盛行,高层偏东风控制等。目前南海夏季风指数的定义基本上都是利用南海局地的变量,也许从更大尺度考虑南海夏季风指数的定义会避免一些天气过程的影响。影响南海夏季风爆发的因素包含了海洋和陆地与大气的相互作用过程,气候模式(包括全球和区域)在季风区关于这方面的描述还有缺陷,而且人为因素的影响加大了气候模式对南海夏季风的模拟和预测的不确定性。

South China Sea summer monsoon (SCSSM) is an important system to affect the rainfall over China, and the onset represents the development of summer circulations over East Asia. The evident circulation changes (including the western Pacific subtropical high shifting off from South China Sea, prevailing low-level southwesterly wind and high-level leaning east wind over South China Sea, etc.) occur from pre-onset to onset. Local variations are often adopted to define SCSSM indices, while a SCSSM index taking large-scale circulations into account can avoid some effects from synoptic-scale processes. Air-sea and air-land interactions are main factors impacting on the SCSSM onset, descriptions of which are defective in GCMs (global and regional). Moreover, artificial effects increase the uncertainty of GCM’s SCSSM simulation and forecast.