中文摘要：

对1980—2014年的NCEP/NCAR 500 hPa高度场逐日格点资料进行Butterworth带通滤波,通过周期分析和最优子集回归方法,利用预报日前150 d的低频数据对2011—2014年全球逐年6—8月500 hPa低频高度场的低频信号进行逐日外延（至未来30 d）,并对其结果进行检验.结果表明,周期分析和最优子集回归方法对500 hPa高度场对应的低频信号的拟合效果从整体上来看,北半球好于南半球,低纬度好于高纬度;随着预报时效的增长,拟合准确度逐步降低,后期趋于稳定.中国对应6个关键区的拟合效果显示,除新疆地区在第10天和第30天未通过信度检验之外,其余5个关键区均通过95%以上的信度检验.该方法对低频系统高低中心配置及落区拟合较好,符合利用低频天气图进行延伸期预报的相关思路,可在该方法的基础上,利用低频天气图方法进行预报.

英文摘要：

The NCEP/NCAR daily grid data of 500 hPa low-frequency height field from 1980 to 2014 were first processed by the Butterworth band pass filter and then by period analysis and optimal subset regression methods;after that the low frequency data of 150 d before the forecast day were used to extend the low frequency signal of 500 hPa low-frequency high field to future 30 d in the whole globe from June to August in the years 2011-2014,to test the forecast results,which are：on the whole,the low frequency signals of 500 hPa lowfrequency height field fitting effect of the northern hemisphere was better than the southern hemisphere,and the low latitude was better than the high latitude;with the increase of the forecast time,the fitting accuracy was gradually reduced and the latter tended to be stable.The fitting effects of the 6 key regions in China showed that except Xinjiang area in the first 10 d and 30 d that did not pass the reliability test,the other 5 key regions got more than 95%in reliability test.The method fitted well in the high and low center configuration of low frequency system and the falling zone,which was in accordance with the use of the low frequency weather map for the prediction of the extended period,and the low frequency weather chart could be used to make an extend ed range forecast on the basis of the method.