国家气候中心海气耦合模式汛期降水预报的一种订正方案及其试验

An Approach and Its Tests to Improve Simulated Summer Rainfall Fields of National Climate Center Coupled Ocean-Atmosphere Model

用奇异值分解(SVD)方法,分析了1983～2003年夏季国家气候中心海气耦合模式500hPa高度预报场与中国特别是华中区域降水场、1971～2000年夏季NCEP/NCAR500hPa高度场与中国特别是华中区域降水场的关系。结果表明:夏季NCEP/NCAR500hPa高度场与中国特别是华中区域降水场关系明显较模式500hPa高度场密切,若夏季NCEP/NCAR500hPa高度场南、北半球副热带高压较强(弱),北半球副热带高压主体偏南(北),则长江流域、东北地区中部及青藏高原东侧将降水偏多(偏少)。对比分析结果,发现国家气候中心海气耦合模式存在一定程度的预报误差,如长江流域误差就较为明显。作者提出一种订正方案,利用SVD从模式500hPa高度预报场中提取大尺度信号,借助最优化技术,合理订正误差,改进降水场的预报。经试验表明:订正后降水场预报的距平同号率有可能接近NCEP/NCAR500hPa高度场相当的技巧水平。

With singular value decomposition(SVD),the relationships between simulated summer 500 hPa height fields of National Climate Center coupled ocean-atmosphere model and rainfall fields over both of China and the middle areas of China during 1983—2003,the relationships between summer NCEP/NCAR 500 hPa height fields and rainfall fields over both of China and the middle areas of China during 1971—2000 have been analyzed. The results indicate that summer NCEP/NCAR 500 hPa height fields have far more close relations with rainfall fields over China than simulated summer 500 hPa height fields of National Climate Center coupled ocean-atmosphere model. When southern and northern hemisphere subtropical high of NCEP/NCAR 500 hPa height is higher(lower),and northern hemisphere subtropical high is located more southward(more northward), heavier(lighter) rainfall will be over the Yangtze River valley, the east side of the Qinghai-Xizang Plateau and the middle of the Northeast China in summer. Comparing the results there are some errors found in coupled-atmosphere model of National Climate Center, for example, the Yangtze River valley has obvious errors. In this paper a project has been proposed in order to improve the simulated rainfall fields by that large scale signals are extracted from the model out simulated 500 hPa height fields by SVD to reduce errors reasonably with optimization. It has been proved by tests that it is probable that the skill of improved simulated rainfall fields is close to NCEP/NCAR 500 hPa height fields.