欧亚地区夏季大气环流年际变化的关键区及亚洲夏季风的关联信号

本文利用资料分析和数值模拟方法研究了欧亚地区夏季大气环流的相关性及其与亚洲夏季风的关联信号,以期为欧亚地区的气候变异及可预测性研究提供科学依据.结果表明:欧亚区域同期(JJA)500 hPa高度场年际变化的关键区包括热带区、中纬度的贝加尔湖和巴尔喀什湖之间以及欧洲地中海附近地区;表面气温的关键区主要位于热带海洋;海平面气压的关键区包括热带的海洋性大陆区域、印度洋和非洲大陆赤道附近部分区域、中高纬的贝加尔湖与巴尔喀什湖之间的地区.另外,夏季大气环流年际变化的春季关键区明显西移/南退,特别是表面气温(其西太平洋区不再是关键区).公用气候系统模式CCSM4.0的大气模式在给定海温年际变化的情况下对于上述大气环流相关场及其关键区的模拟基本合理,其中500 hPa高度场的模拟结果较好,海平面气压场的结果逊之;对于同期和前期的结果,模式都有夸大西太平洋海温影响的倾向.对于东亚夏季风指数与大气环流的同期年际变化信号而言,其空间分布基本表现为以30°N为界呈西南东北向的波列状分布;其春季前期信号中,30°N以南的显著区几乎都位于海洋,30°N以北主要位于欧洲、巴尔喀什湖与贝加尔湖之间的地区.南亚夏季风指数的前期显著相关区比同期明显西移/南退.总之,模式的模拟结果和观测结果相当吻合,但其同期模拟结果比前期的更好一些.这些结果说明:模式对于大气环流年际变化的耦合变化信息的刻画是基本合理的,这为利用气候模式进行有关可预测性研究和降尺度预测研究奠定了基础.

The key areas of interannual variability of the Eurasian summer general circulation and the signals of the Asian summer monsoon variability

Based on NCEP/NCAR reanalysis data and climate model simulations, the relationship among Eurasian summer general circulation and associated signals of the Asian summer monsoon are analyzed. The results indicate that the key areas of the interannual variation of June-July-August 500 hPa heights over Eurasia include the tropical region, the mid-latitude areas which encompass the area between Baikal and Balkhash, and the region surrounding Mediterranean. The key area of surface atmospheric temperature primarily locates over the tropical ocean. The tropical maritime continent, the Indian Ocean and part of the equatorial area over African continent are the key areas of sea level pressure. In addition, the key areas for March-April-May are located more westward or southward, especially for the surface air temperature (the western Pacific is no longer the key area). Forced by given SST interannual variation, the atmospheric model CAM4 shows reasonable simulation abilities on the key areas mentioned above, with the best performance for 500 hPa heights. In the simulations, the model shows excessive roles of the western Pacific as compared to the observation. With respect to signals of the East Asian summer monsoon index, the spatial pattern resembles a southwest-northeast pattern which is bordered by 30°N. The preceding signals in spring are located both over the ocean south of 30°N, and over the Europe and the regions between Baikal and Balkhash. In conclusion, the model results are in general agreement with the observation, with better performance for the signals in summer than in spring, which lays a good foundation for related model-based predictability and downscaling researches.