Opposite summer precipitation anomalies over the Maritime Continent in fast and slow decaying El Niño cases

Abstract

Summer precipitation over the Maritime Continent (MC) is tightly connected to livelihoods of the locals, and the corresponding strong convective activities are also crucial to Asian regional climate variations remotely. Using observational and reanalysis data from 1958 to 2020, we found that El Niño with different decay rates can cause different summer precipitation anomalies in the MC area. In the fast decaying (FD) El Niño summer, the MC area shows a precipitation surplus, while the MC precipitation decreases during the slow decaying (SD) El Niño summer. For the FD El Niño, the equatorial central-eastern Pacific warm sea surface temperature (SST) anomaly quickly turns into cold in the decaying summer, while the SST over MC region sustains a warm anomaly owing to the Indo-western Pacific Ocean capacitor effect. This local warm SST anomaly leads to anomalous ascent and then excessive precipitation, further stimulating low-level easterly wind to east of the MC with increased water vapor transport. For the SD El Niño, the central-eastern Pacific warm SST anomaly sustains till the decaying summer, continuously adjusting the Walker circulation. An anomalous local descent motion associated with the weakened Walker circulation region hampers the MC precipitation in summer. Our findings benefit the local researches of the MC summer climate variations, and potentially favor the regional climate predictions.