欧亚季节环流气候平均态和气候变率：20CR再分析资料在欧亚及中国东部地区的评估

Eurasia Seasonal Circulation Climatology and Variability:Evaluation of20CR Reanalysis Data in Eurasia and East China

本文评估了美国国家大气海洋局(NOAA)新发布的20世纪再分析资料(20CR)对欧亚季节环流气候平均态和气候变率及中国东部气温降水的刻画能力。结果表明:20CR再分析资料对欧亚地区四季环流气候平均态刻画能力与NCEP2资料的相比,均呈现北部中高纬度系统性偏高,南部中低纬度系统性偏低的特点,导致描绘的东亚冬季风偏弱,夏季风偏强。这可能与20CR资料在极地海岸地区海冰资料处理时产生的差错有关。与中国东部的站点资料对比则显示20CR对我国东部气温的刻画偏低,而对降水的刻画偏高,站点相关性气温好于降水,东南沿海地区优于内陆地区。平均场和空间相关场结合来看,秋季气温和降水20CR与站点观测资料吻合最好。20CR资料较好地刻画近百年北半球冬夏季的气候指数(北极涛动、北大西洋涛动、北太平洋涛动、东亚冬季风、阿留申低压等)的年际变率及年代际变化特征,很好地刻画了阿留申低压1970年代末的年代际增强,西伯利亚高压1970年代末的下降和1990年后的上升趋势及北太平洋涛动、北大西洋涛动和北极涛动指数1970年代末期由负位相到正位相的年代际转变。

This study evaluates the characterization capabilities of seasonal Eurasia climatology and climate variability of the newly released twentieth century reanalysis （20CR） data by the U.S. National Oceanic and Atmospheric Administration. The results shows that in the Eurasia area, the 20CR data exhibited higher values in the northern high latitudes and lower values in the southern low latitudes than those recorded by version II of the National Centers for Environmental Prediction reanalysis data, resulting in weaker winter monsoon and a stronger summer monsoon circulations. This may be partly attributed to the handling of specified sea-ice concentration in the polar coastal area in the 20CR data. Comparison with the station observation data of eastern China indicates that the 20CR data representslower air temperature and a higher precipitation in the four seasons whereas the correlation of temperature between 20CR reanalysis data and the station observation is higher than that of precipitation. In addition, the variability of temperature and precipitation over the southeastern coastal area were captured better than those of the inland areas in 20CR reanalysis data. In particular, the highest consistency of the temporal-spatial feature of autumn temperature and precipitation in eastern China was between 20CR data and station observations. Major climate variability indices such as Arctic oscillation （AO）, North Atlantic oscillation （NAO）, North Pacific oscillation （NPO）, Aleutian low, Siberian high, East Asian summer monsoon, East Asian winter monsoon, and Southern oscillation （SO） recorded during the last hundred years have also been evaluated in 20CR reanalysis data. The 20CR reanalysis data and the Hadley Centre sea level pressure dataset both showed the decadal change characteristics that the winter Aleutian low deepened during the late of 1970s, whereas the Siberian high weakened during the same period and intensified in the 1990s. In addition, negative phases of winter AO, NAO, and NPO transferred to positive phases during the late 1970s.