Possible Influence of ENSO Modoki and Arctic Oscillation on Spatiotemporal Variability of Spring Precipitation Over the Western North Pacific

There are two leading modes in boreal spring precipitation over the western North Pacific (WNP). The first leading mode is a dipole pattern between the southern China and Southeast Asia, which have been previously investigated. The second leading mode is a tripole pattern, which this study focused on. The pattern shows that the positive cores are located in the midlatitudes and the tropical WNP, respectively, whereas the negative one extends from the subtropics to the South China Sea. The mode of tripole pattern is predominantly responsible for the actual spring precipitation variation in the subtropics (r = − 0.93). On the other hand, the precipitation variations in the midlatitudes, the tropical WNP, and the South China Sea are not well explained as much as that in the subtropics. The tripole-pattern-related circulation resembles the positive phase of North Pacific Oscillation, possibly associated with the El Niño Modoki and the positive phase of Arctic Oscillation. The circulation corresponds to the northward shift of the WNP subtropical high, which contributes to the precipitation increase and decrease in the midlatitudes and subtropics, respectively. Meanwhile, the weakened Walker circulation in tropical western Pacific accounts for the decreased and the increased precipitation in the South China Sea and the tropical WNP, respectively. The opposite is true for the circulations related to the La Niña Modoki and negative phase of Arctic Oscillation.