The Dipole Mode of Asia-Pacific Sea Level Pressure Anamalies in Winter and Its Relation to SST

The anomaly mode of the Asia-Pacific (20°N-70°N, 40°E-120°W) sea level pressure in winter is studied, using the methods of rotated empirical orthogonal function decomposition (REOF), Morlet wavelet analysis, correlation analysis, and synthesis analysis on the global monthlyaverage Sea Level Pressure (SLP) and Sea Surface Temperature (SST). Then the relationship between SLP anomaly (SLPA) and SST anomaly (SSTA) is studied. The results show: The Asia-Pacific winter SLP has a nearly-zonal dipole (anti-phase) distribution, as well as an obvious meridional dipole (anti-phase) distribution. The most significant anomalies of winter SLP are in the four areas which locate in Northeast Asia (60°N-70°N, 110°E-150°E), subtropical North Pacific (25°N-35°N, 150°E-170°W), northwest of China (35°N-45°N,85°E-110°E), and the Aleutian Islands (50°N-60°N, 170°E-165°W). There is a significant negative correlation of SLP between Northeast Asia and the subtropical North Pacific, as well as Northwest China and the Aleutian Islands, which shows the existence of meridional dipole oscillation and zonal dipole oscillation. Two dipoles obviously change at interannual scale with a period of 3-4 a, while zonal dipole index has a cycle of 16 a or so at interdecadal scale in addition.