244 / 2024-09-12 15:53:25

The connection between sea surface temperature anomaly over tropical south Atlantic and ENSO and the associated impact on East Asian climate

Tropical south Atlantic,ENSO,East Asian climate

The tropical Atlantic, as a vital component of the tropical oceans, exerts significant influence on both local and global climates through its sea surface temperature variability and interactions among tropical basins. We found a significant influence of the sea surface temperature anomaly over tropical south Atlantic (TSA-SSTA) on ENSO Events and the Meiyu onset date. A significant negative correlation between the preceding TSA-SSTA and subsequent summer ENSO events was revealed. The warm (cold) TSA-SSTA corresponds to the following summer La Niña (El Niño)-like SSTA in the tropical Pacific. Warm TSA-SSTA can trigger local anomalous upward motion, resulting in precipitation and positive Walker circulation anomalies in the equatorial Pacific. This configuration facilitates the strengthening of easterly anomalies in the lower level of the equatorial Pacific, further promoting the development of La Niña-like SSTA in the central to eastern equatorial Pacific. These mechanisms and conclusions remain valid even after linearly removing the signal of the preceding winter ENSO. At the same time, when TSA-SSTA is warm the Meiyu onset date tends to be early. This is because that warm TSA-SSTA triggers significant positive Gill responses in the equatorial Pacific, further generating local anticyclonic circulation anomalies over the Maritime Continent of the northwest Pacific. Under the combined effects of large-scale forcing and the "precipitation-circulation Sverdrup positive feedback" mechanism in the northwest Pacific, anomalous anticyclones can develop and be sustained, resulting in an earlier Meiyu onset date. Furthermore, the interannual relationship between the TSA-SSTA and ENSO also exhibits decadal variability, closely related to the Pacific Decadal Oscillation (PDO).