ERA40中北半球高纬地区冬季气候变化和冰-气相互作用特征分析

WINTER CLIMATE CHANGE AND CHARACTERISTICS OF SEA ICE-ATMOSPHERE INTERACTION IN NORTHERN HIGH LATITUDES FROM THE ERA40

利用欧洲中期天气预报中心(ECMWF)再分析资料(ERA40)分析了最近几十年冬季北半球高纬地区的气候变化和冰-气相互作用特征。在全球增暖背景下,冬季北半球高纬地区增温幅度更大,但温度变化明显具有区域性特点。20世纪70年代末期开始,格陵兰海、巴伦支海及欧亚大陆大部分区域和北美大陆部分区域在增暖,而拉布拉多海、格陵兰和白令海峡区域却变冷。与此对应,中央北极区及气候冰岛低压中心海平面气压在降低,而再往南区域海平面气压在升高。从20世纪70年代开始,格陵兰海和巴伦支海给大气的感热通量和潜热通量增多,这说明由于气温增加,使得海冰密集度减小,海冰对海气感热通量和潜热通量交换的隔离层作用减小,通量交换大大增加。而在挪威海非海冰区,由于气温增加,海气温差减小,海洋给大气的感热通量和潜热通量减少。在拉布拉多海,由于气温降低,海气温差增大,使得海洋给大气的感热通量和潜热通量增加,有利于拉布拉多海海冰的增多。海平面气压、海冰密集度及表面感热通量和潜热通量之和对大气表面温度 EOF 展开第一模时间系数的线性回归结果均与各自的EOF 展开第一模空间分布特征接近。

Based on the European Center of Medium Range Weather Forcast （ECMWF） reanalysis dataset （ERA40）, winter climate change and characteristics of sea ice-atmosphere interaction in northern high latitudes for recent several decades are analyzed. Under the background of global warming, the amplitude of temperature increase in winter in northern high latitudes is getting bigger and it has different features in different regions. From the end of 1970s, the Greenland Sea, the Barents Sea and the most part of Euro-Asian continent and North American continent are getting warmer, whereas the Labrador Sea, the Greenland and the area around the Bering Strait are getting colder. Meanwhile, the sea level pressure in the center part of the northern polar region and the region where the climatic Icelandic low exist decreases, but in places farther southward it increases. Since the 1970s, the sensible heat flux and latent heat flux sent to the atmosphere from the Greenland Sea and the Barents Sea has increased, this is mainly due to the reduction of sea ice concentration and the weakening effect of insulator and shield of the solid ice accordingly caused by the increase of air temperature. In sea ice free area of the Norwegian Sea, the sensible heat flux and latent heat flux sent to the atmosphere has reduced due to decrease of temperature difference between the air and the sea surface caused by increase of air temperature. In the Labrador Sea, due to decrease of air temperature and increase of temperature difference between the air and the sea surface accordingly, the sea gives more sensible heat flux and latent heat flux to the air. This will lead to the growth of sea ice extent there. The features of linear regression of sea surface pressure, sea ice concentration and sum of sensible heat flux and latent heat flux toward time series of the leading mode of EOF expansion of surface air temperature are close to those of their own EOF expansion for the leading mode respectively.