Relationship between the Meridional Dipole Mode of Sea Level Pressure Anomalies in Asia–Pacific Region and SST Anomalies in the Northwestern Pacific Determined by Sensitive Experiments with General Circulation Model

Through data analyses and sensitive experiments with the general circulation model (GCM), the relationship and influence of the sea surface temperature anomalies (SSTA) in the North Pacific on the meridional dipole mode of sea level pressure (SLP) in the Asia-Pacific region are studied in this paper. The data analyses show two critical regions of SSTA in the northwestern Pacific corresponding to the anomalous meridional dipole mode of the SLP in winter in the Asia-Pacific region. In particular, the SSTA in the (40°N-55°N, 150°E-160°W) region shows a positive correlation and that in the (20°N-35°N, 125°E-170°W) region shows a negative correlation to index I_ME of the meridional dipole mode of the SLP. The data analyses also show that the impact of SSTA in those two critical regions on the meridional dipole mode of the SLP in the Asia-Pacific region is mainly passed through the effect of heat flux anomalies. The results of sensitive experiments with the GCM show that the SSTA in two critical regions of the Northwestern Pacific play a specific role in exciting the meridional dipole mode of the SLP in winter in the Asia-Pacific region. In region I (42°N-62°N, 145°E-165°E), the negative SSTA is more effective than the positive SSTA in exciting the negative phase of the meridional dipole mode of the SLP; the positive SSTA in region II (22°N-42°N, 135°E-175°E) and (26°N-42°N, 175°E-170°W) is more effective than the negative SSTA in region I in exciting the negative phase of the meridional dipole mode of the SLP. However, the position of the excited negative meridional dipole mode of the SLP deviates a certain distance when there is negative SSTA in region I alone or positive SSTA in region II alone. Because the negative SSTA in region I coordinates with the positive SSTA in region II, the excited negative meridional dipole mode of the SLP is remarkable.