Abstract:
Based on the ERA-Interim reanalysis data from 1979 to 2016 and numerical modeling simulations (CAM5.3), the present study investigates impacts of the North Atlantic Sea surface temperature (SST) anomalies on China rainfall during the summer of 2016 and 1998 and the possible physical mechanisms during summer of 2016 and 1998 are investigated in the present study. It is suggested that the difference in the North Atlantic SST anomaly patterns between 2016 and 1998 makes important contribution to differences in eastern China summer rainfall and the associated circulation anomalies. The pattern of rainfall anomalies during the early summer (June-July) of 2016 was similar to that in 1998, except for more rainfall in the southern of Yangtze River valley in 1998. However, the patternss of rainfall anomalies during the late summer (August) were almost opposite in between these two years. The differences in summer rainfall anomalies between 2016 and 1998 were directly resulted from circulation anomalies in the Northwest Pacific and the Eurasian mid-high latitudes, which were both closely linked to the North Atlantic SST anomalies. On one hand, the North Atlantic SST anomalies could exert a downstream impact on the early summer rainfall of 1998 by inducing a Rossby wave-trains over the Eurasian mid-high latitudes, which was favorable for more rainfall in southern China. However, while the response of Eurasian circulation to the North Atlantic SST forcing was relatively weak in 2016. On the other hand, the North Atlantic SST anomalies could also exert an impact on the circulation over the Northwest Pacific through a westward propagating subtropical teleconnection. In both the early and late summer of 1998, the North Atlantic SST forcing was consistent with that of the tropical Indo-Pacific SST forcing, which resulted in a strong anomalous low-level anticyclone over the Northwest Pacific. However, the anomalous low-level anticyclone in early summer of 2016 was weaker than that in 1998 due to the opposite impacts of the SST anomalies in between the North Atlantic and the tropical Indo-Pacific Ocean. In contrast, an anomalous low-level cyclone was observed over the Northwest Pacific due to the dominant impact role of North Atlantic SST forcing in late summer of 2016.