Using observational data, the East Asian-North Indian Ocean index （]EANI）, which reflects a tropospheric thermal contrast, is found to correlate well with the East Asian summer monsoon （EASM） and associated rainfa...Using observational data, the East Asian-North Indian Ocean index （]EANI）, which reflects a tropospheric thermal contrast, is found to correlate well with the East Asian summer monsoon （EASM） and associated rainfall over eastern China. Corresponding to a higher （lower） IEANI, the EASM at mid-latitudes is stronger （weaker）, and there is more （less） rainfall in North China and less （more） rainfall near the Yangtze River valley. To investigate long-term variation in the EASM, we reconstructed the BC 665AD 1985 IEANI based on reconstructed temperatures in Beijing and Tasmania, Australia. Over the past 2000 years, the reconstructed/EANI generally represents centennial-scale variations in the EASM and rainfall over eastem China. The correlation pattern between the reconstructed IEANI and rainfall over eastern China is similar to modem observations, implying that the correlation feature at centennial scales also occurred over the past 2000 years. With respect to longer-scale （several hundreds to one thousand years） IEANI variations and their correlations with rainfall, further verifications should be performed using various paleoclimatic proxy data.展开更多
基金sponsored by National Natural Science Foundation of China (Grant Nos. 40890053 and 40890052)National Basic Research Program of China (Grant No. 2007CB815901)
文摘Using observational data, the East Asian-North Indian Ocean index （]EANI）, which reflects a tropospheric thermal contrast, is found to correlate well with the East Asian summer monsoon （EASM） and associated rainfall over eastern China. Corresponding to a higher （lower） IEANI, the EASM at mid-latitudes is stronger （weaker）, and there is more （less） rainfall in North China and less （more） rainfall near the Yangtze River valley. To investigate long-term variation in the EASM, we reconstructed the BC 665AD 1985 IEANI based on reconstructed temperatures in Beijing and Tasmania, Australia. Over the past 2000 years, the reconstructed/EANI generally represents centennial-scale variations in the EASM and rainfall over eastem China. The correlation pattern between the reconstructed IEANI and rainfall over eastern China is similar to modem observations, implying that the correlation feature at centennial scales also occurred over the past 2000 years. With respect to longer-scale （several hundreds to one thousand years） IEANI variations and their correlations with rainfall, further verifications should be performed using various paleoclimatic proxy data.
