Interdecadal change in the influence of El Niño in the developing stage on the central China summer precipitation

The central China summer precipitation (CCSP) is of great importance to the people’s livelihood of this densely populated region, including the agriculture, ecosystems, water resources, economies, and health. Based on the observed precipitation, sea surface temperature (SST), and atmospheric reanalysis datasets, the present study investigates the effects of El Niño in the developing stage on the CCSP during 1960–2014. The results show that the CCSP anomalies exhibit significant negative correlations with the El Niño-related SST anomalies in both the simultaneous summer and the following winter, implying that the developing El Niño is important for modulating the CCSP. However, this climatic teleconnection of El Niño is unstable, with an obvious interdecadal change around the late 1980s. Specifically, the negative correlation is not statistically significant in the previous epoch before the late 1980s (1960–1988), but dramatically strengthens since the late 1980s (the post epoch for 1989–2014). Such an interdecadal change is closely associated with the change of the El Niño-related SST anomaly pattern. Compared to the previous epoch, the central Pacific El Niño occurs more frequently in the post epoch, leading to an interdecadal shift of the maximum warm SST anomalies from the eastern Pacific to the central Pacific. The resultant westward extension of the atmospheric circulation responses induces an anomalous low-level cyclone covering South China in the post epoch. It would prevent the southwest monsoon from delivering the moisture to the north and hence reduce the CCSP. While, in the previous epoch, the anomalous cyclone locates east of South China, exerting insignificant influence on the CCSP. This work highlights a strengthening effect of El Niño on the CCSP since the late 1980s, with great implications for the regional seasonal climate prediction.