Relationship of Atmospheric Circulation Factors in the Preceding Winter with the Coupling Intensity of the Western Pacific Subtropical High and Northern East Asian Low

The western Pacific Subtropical High (WPSH) and Northern East Asian Low (NEAL) are the main pressure systems influencing summer rainfall (SR) over the Democratic People’s Republic of Korea (DPRK). A new coupling index is constructed which determines the interannual variability in SR over the DPRK. The correlation coefficient (CC) between the interannual variabilities of this coupling index and SR over the DPRK is 0.55. An abrupt change in the coupling index WPSHI + NEALI time series appeared around the early 1970s. During the study, four atmospheric circulation indices for the seasonal prediction of this coupling index were found. Also, the possible mechanisms of the connection between WPSHI + NEALI and these indices in preceding winter were investigated. The back propagation (BP) neural network model was used to obtain and analyze the prediction results of WPSHI + NEALI with different predictor combinations. The prediction results show that the predictor combination of the AOI (Arctic Oscillation Index), SHI (Siberian High Index), and EATI (East Asian Trough Index) gives the best prediction skill with CC = 0.92 ( $$p<0.001$$ ) and RMSE = 0.13 for the independent test interval.