Study Of Summer Tropical Indian Ocean SST Influence On Interannual And Interdecadal Variation Of The PJ Teleconnection Pattern

Based on ERA-40, NCEP/NCAR monthly reanalysis dataset, Hadley SST monthly dataset, precipitation dataset from PREC/L, PREC and CMAP, summer tropical Indian Ocean (TIO) Sea surface temperature (SST) influence on interannual and interdecadal variation of the Pacific-Japan (PJ) teleconnection pattern are investigated by meteorological statistical methods such as singular value decomposition (SVD) and numerical simulations. The main conclusions are as follows:A new PJ index is introduced by using the SVD method onto the summer 500 hPa height in East Asia and precipitation near the Philippines. This index is not only have clear physical meaning, and be able to clearly reflect the interannual and interdecadal variation of the PJ pattern.This study also shows that the interannual variation of the PJ index is closely related to the El Nino Southern Oscillation (ENSO) event. El Nino teleconnection causes TIO SST to increase like a battery charging a capacitor, and these increased temperatures exert the formation of anomalous anticyclones near the Philippine Sea. In addition, ENSO events stimulate the PJ teleconnection pattern along the coast of East Asia. The variations of SST in Philippine Sea are not the reason of the interannual and interdecadal variations of the PJ pattern. Instead, these SST anomalies over the Philippine Sea result from the occurrence of anomalous anticyclones (cyclones) producing increased (decreased) radiation, decreased (increased) evaporation, deepened (shallowed) thermocline, and higher (lower) SST. The increased SST in this area corresponds to weakened convection and decreased precipitation over northeast Asia.When TIO SST warm in summers, will cause suppressed convection and anomalous descending motion over Philippines, result in anomalous anticyclones maintain, and stimulate the "anticyclone, cyclone, anticyclone" PJ pattern along the coast of East Asia. Effect by anomalous anticyclones in Philippines, SST in Philippine Sea and South China Sea is also warm. This cause anomalous vertical motion and anomalous moisture transportation over East Asia. Therefore, increase precipitation over the Jianghuai region and Japan to the east, but decrease precipitation over western pacific, southern China and Okhotsk Sea. When TIO SST cold in summers, will cause enhanced convection and anomalous ascending motion over Philippines, result in anomalous cyclones maintain, and stimulate the "cyclone, anticyclone, cyclone" PJ pattern along the coast of East Asia. Effect by anomalous cyclones in Philippines, SST in Philippine Sea and South China Sea is also cold. Therefore, increase precipitation over western pacific and Okhotsk Sea, but decrease precipitation over the eastern China and Japan to the east.Use of reanalysis data shows that the PJ pattern switching from "cyclone, anticyclone, cyclone" to "anticyclone, cyclone, anticyclone" in last 1970s. The interdecadal variation of PJ pattern is related to the continuous increases TIO SST. While the steady warming TIO SST sustains the anticyclone anomaly near the Philippine Sea since the late 1970s, and forms the interdecadal variation of PJ pattern. The steady warming of SST in Philippines may results from the anomalous anticyclone near the Philippine Sea. Furthermore, numerical simulations performed with the atmospheric circulation model European Centre Hamburg Model5.4 (ECHAM5.4) showed that when the TIO SST increases, anticyclones are exerted near the Philippine Sea and stimulate the "anticyclone, cyclone, anticyclone" PJ pattern along the coast of East Asia.