摘要
Summer rainfall variations in North China closely relate to that in India. It seems that an alternation of signs of“＋, -, ＋” exists in the geographical pattern of the correlation in summer rainfall from North China to India through the Tibetan Plateau. However, it appears that the teleconnection of summer rainfall variations between North China and India is unstable. Over 1945 - 1974, the correlation coefficient （hereafter as CC） is as large as 0.7. In contrast, the CC is about -0.3 over 1827-1856. Further studies, based on observations starting from 1813, showed that the correlation is strong when summer rainfalls in both North China and India are large, and vice versa. In order to find what induce the change of the teleconnection, variations of summer rainfall in both North China and India, mean sea surface temperature （SST） in the eastern equatorial Pacific and the frequency of ENSO events were examined in relation to the change of the teleconnection. The result showed that the teleconnection appears weak when the mean SST is high and the frequency ofLa Nifia events is low; the teleconnection is strong when the mean SST is low and the frequency ofLa Nina events is high. At last, it is notable that La Nifia happens in only 3 years during the recent 30 years from 1976 to 2005 and the teleconnection becomes weak too.
Summer rainfall variations in North China closely relate to that in India. It seems that an alternation of signs of "+, -, +" exists in the geographical pattern of the correlation in summer rainfall from North China to India through the Tibetan Plateau. However, it appears that the teleconnection of summer rainfall variations between North China and India is unstable. Over 1945 - 1974, the correlation coefficient (hereafter as CC) is as large as 0.7. In contrast, the CC is about-0.3 over 1827-1856. Further studies, based on observations starting from 1813, showed that the correlation is strong when summer rainfalls in both North China and India are large, and vice versa. In order to find what induce the change of the teleconnection, variations of summer rainfall in both North China and India, mean sea surface temperature (SST) in the eastern equatorial Pacific and the frequency of ENSO events were examined in relation to the change of the teleconnection. The result showed that the teleconnection appears weak when the mean SST is high and the frequency of La Nia events is low; the teleconnection is strong when the mean SST is low and the frequency of La Nia events is high. At last, it is notable that La Nia happens in only 3 years during the recent 30 years from 1976 to 2005 and the teleconnection becomes weak too.
基金
Diagnosis and simulation of decadal variability of East Asian summer monsoon and summerprecipitation in Eastern China (40331010)
