A Study On The Relationship Between The Temporal Variability Of SSTA In The Middle And East Equatorial Pacific And East Asian Summer Monsoon

This Master thesis suggests a new idea that the temporal variability of SSTA in the middle and east equatorial Pacific in the next year of El Nino and La Nina has an effect on East Asian summer monsoon and summer rainfall in China. Firstly, the correlations between the temporal variability of SSTA from March to August in Nino1+2, 3, 4, 3.4 and summer rainfall in China are analyzed. The results show that there is a negative correlation between the four region's temporal variability of SSTA and summer rainfall over the south of Yangtze River, North China, especially the Nino3.4 region. Furthermore, the correlation between the temporal variability of SSTA in Nino3.4 region and the vertical shear of zonal wind over the east Asia is analyzed. The result shows that there is a weak positive correlation with South China Sea summer monsoon. Based on the correlation analyses above mentioned, the variability of SSTA in Nino3.4 region can be regarded as a prediction signal for seasonal prediction to conduct further studies in this thesis.According to the temporal variability of SSTA in Nino3.4 region, ten years with positive and negative temporal variability of SSTA respectively are selected to conduct a composite analysis to examine the difference of high & low level's atmospheric circulation and summer rainfall in China. There are significant differences in the east Asian monsoon circulation and height field in different regions, especially in the south of Yangtze River, South China Sea and Northeast China. Therefore, the temporal variability of SSTA in Nino3.4 region can provide a prediction clue for the prediction of East Asian summer monsoon and China summer precipitation. For the further verification, the simulation of CAM2 model also shows that there are quite great difference in high/low level's circulation and rainfall in the years of different temporal variability of SSTA in the middle and east equatorialPacific.Finally, some sensitive experiments are carried out to find out the impact of different temporal variability of SSTA in the middle and east equatorial Pacific on the potential predictability of east Asian summer monsoon, which give some interesting conclusions: if the temporal variability of SSTA in middle and east equatorial Pacific is increasing, the potential predictability of not only the high & low level circulations and 500 hPa heigh, but also the precipitation and surface temperature will become higher over the South China Sea, south of Yangtze River and Northeast China. Furthermore, the change of potential predictability in tropics is lower than that of mid-high latitudes. The potential predictability in the years of negative temporal variability of SSTA is higher that in the positive ones.