The intertropical convergence zone (ITCZ) is a narrow heavy tropical rain belt around the globe and plays an important role in the global water cycle. The western Pacific has a distinct double ITCZ structure, with one ITCZ located in the Northern Hemisphere and the other in the Southern Hemisphere. The change of the double ITCZ in their variability and trend under the warming climate can affect the regional and global climate and the hydrological cycle, therefore the society and ecosystems. Meanwhile, the modern coupled climate models still cannot simulate the ITCZ adequately compared with observations. Using the observations, atmospheric reanalysis and the climate model simulations, we investigated the seasonal and interannual properties of double ITCZs in western Pacific (130-220°E and 25°S-25°N). Results show that the precipitation variability in this region is dominated by the horizontal moisture convergence. The trend of the change in the ITCZ latitudinal position north of the equator is inconsistent across models, but the southward shift of the south Pacific convergence zone (SPCZ) is consistent and significant across datasets, it is shifting away from the equator at the rate of -0.20±0.05 °decade-1 when the centroid method is used and -0.44±0.13 °decade-1 when the maximum precipitation method is used. The intensities of double ITCZs in the study region vary with the moisture convergence and their latitudinal location follows the maximum SST position.

Double ITCZs, Climate Change, Sea Surface Temperature, Western Pacific