中文摘要：

介绍了Lamb-Jenkinson客观环流分型方法。利用1948年1月1日—2004年12月31日的NCEP逐日平均海平面气压资料,计算了中国16个区逐日的6个环流指数及相应的环流分类,分析了中国各区域不同季节各种环流类型出现的频率及其变化特征。结果表明,该方法在我国大部分地区适用,虽然在西部高海拔地区的海平面气压可能有订正误差,但该方法是可行的。对1958—2004年以来3个主要环流指数的线性趋势分析显示,华北及河套至内蒙古中西部地区夏季的经向风指数和纬向风指数下降明显,涡度指数也有明显的下降,表明控制上述地区的高值系统有增多趋势,而准地转西南风减弱,这可能是造成这些地区干旱化的重要环流背景。对冬季而言,我国东北、华北和新疆北部等地区的纬向风指数上升明显,表明我国北部地区冬季的近地层西风有加强的趋势,这与近年来这些地区冬季气温显著升高有密切关系。

英文摘要：

In this study, the Lamb-Jenkinson circulation type classification system is applied to obtain circulation information in China on daily basis. For that purpose, the NCEP daily mean sea-level pressure reanalysis data from 1 January 1948 to 31 December 2004 are used to derive daily six circulation indices and corresponding 27 circulation types for 16 sub-regions in China. The frequency of circulation types over different sub-regions and seasons is computed and described. Results show that Lamb-Jenkinson classification system is applicable for most of China, although in the west of China where might exist some errors in sea-level pressure due to high elevation. Linear tendencies of three major indices （ zonal wind,meridional wind and vorticity） from 1958 to 2004 has been analyzed. Since 1958 ,all of three indices have obviously decreased over North China,Hetao and central-western Nei Mengolia, which indicates that high value systems have increased and quasi-eostrophic southwest wind has decreased over these regions. It is possibly an important circulation background for droughts over above regions. For the wintertime, zonal wind index has distinctively increased over Northeast China, North China and the north of Xinjiang, suggesting that the westerly in the ground layer has strengthened over the north of China, which is closely related with remarkable warming over above areas in winter.