资源环境科技发展态势分析平台

Using observational data and numerical experiments, the decadal relationship between South Pacific and rainfall over southeastern China during boreal autumn is examined. In the observational analyses, it is found that the boreal autumn South Pacific shows significant decadal variability with a significant periodicity of 11-21years from 1960 to 2000, which is an independent phenomenon in the whole Pacific. This South Pacific decadal variability can induce significant decadal variability of boreal autumn rainfall over southeastern China. When the boreal autumn South Pacific decadal variability is in its positive phase, less rainfall appears over the southeastern China, and vice versa. The possible physical mechanisms are further investigated. It is suggested that the negative sea surface temperature anomalies (SSTA) in the extratropical South Pacific associated with positive phase of South Pacific decadal variability could result in an anomalous anticyclone to the east of Australia. The cross-equatorial flow over the Maritime Continent and tropical western Pacific is enhanced under the influence of this anomalous anticyclone, favouring the location of western Pacific subtropical high moving more eastwards and then leading to the formation of anomalous cyclone over western North Pacific. To the west flank of this anomalous cyclone is the significantly anomalous northerly, which is favourable for less rainfall over southeastern China. On the other hand, significant negative SSTA appears in the Maritime Continent and tropical western Pacific could cause anomalous sinking motion here, which can further induce anomalous sinking motion over southeastern China through two meridional cells extending from Maritime Continent to southeastern China with a common rising branch over the southern South China Sea, thus resulting in less rainfall over southeastern China. Numerical experiments confirm our observational results.