The relationship between summer tropical Atlantic sea surface temperature and the first rainy season precipitation in South China without ENSO impact

This study emphasizes the impact of the summer (June-August) tropical Atlantic (TA) sea surface temperature (SST) anomalies on the precipitation during the first rainy season (FRS, April-June) of the following year in South China without the influence of the El Niño/Southern Oscillation (ENSO). Correlation and causal analyses combined with atmospheric dynamic diagnostics reveal that summer TA SST anomalies enable the storage of anomalous signals by promoting the development of a tripole SST pattern in the North Atlantic (NA) during the subsequent FRS. Following a lower TA SST in the preceding summer, the NA tripole-like SST anomalies excite a Eurasian Rossby wave train and thus significantly strengthen the Ural Mountain ridge and the cyclonic circulation around Lake Baikal. On the one hand, this process induces the intensification and southward expansion of the subtropical westerly jet, leading to anomalous ascending motion over South China. On the other hand, it facilitates more frequent southward intrusions of mid-high latitude cold air, which enhances low-level frontogenetic forcing over South China. These coupled mechanisms ultimately amplify precipitation.