夏季东亚副热带西风急流特征指数表征方法对比分析

为了能够给科研工作者和业务技术人员合理使用各种东亚副热带西风急流表征方法提供科学依据,利用1960～2009年NCEP/NCAR再分析资料和中国714个基准站20时(北京时)降水观测资料,归纳总结了以往夏季东亚副热带西风急流客观定量表征方法,并以2005年6～8月为例,进行了表征方法的数值反演和性能分析,结果表明:表征位置指数的方法有轴线法、EOF分解法、区域风速差法。轴线法定义合理且有明确的物理意义,方法简单易行、意义清晰、表现直观,适用于逐日实时监测和诊断分析。EOF分解法与区域风速差法适用于气候评估和季节诊断;表征急流强度的方法有区域风速法及中心强度法,均适应于逐日实时监测与环流观测,且对华北地区及长江中下游雨量多寡有较好的指示意义,方法计算简便、意义清晰、指示性好。同时还指出,业务工作者和科研工作者实际应用时应根据需求合理选择指数或者对指数进行适当改进。

Comparison and Analysis of the Characteristic Indexes of Summer Subtropical Westerly Jet Stream Over East Asia

In order to provide scientific basis for investigators and operation departments to use a variety of methods to characterize East Asian subtropical westerly jet(EASWJ) reasonably.Using the reanalysis data during 1960～2009 from NCEP/NCAR and China 714 stations daily precipitation data(Beijing time),taking cases in 2005 for example,characteristic indexes of EASWJ are studied,retrieved numerically and compared based on summary of existing objective,quantitative EASWJ methods.The results show that: there are many methods to characterize the position index such as axis index method,EOF decomposition method and Regional wind speed difference method.The axis index method is defined reasonable,simple,and has clear physical meaning and intuitive performance.It applies to daily real-time monitoring and diagnostic analysis.EOF and Regional wind speed difference method apply to Climate Assessment and Seasonal diagnosis;there are two methods,Regional wind speed and the central intensity,to characterize the intensity index.They are fit to daily real-time monitoring and Circulation observation and have good meaning to Rainfall amount of the middle and lower reaches of the Yangtze River and North China.The methods are objective and quantificational,simple,clear meaning,and good indicative.At the same time,we point that based on what merits and demerits of these EASWJ indexes have,investigators and operation departments should apply EASWJ indexes better if they can select compatible one or improve and innovate a method according to there selves practice.