Strengthening effect of El Nino on the following spring Indian Ocean warming with implications for the seasonal prediction of the Asian summer monsoons

El Nino induces a southwest Indian Ocean (SWIO) warming in decaying springs by forcing the slow-propagating downwelling oceanic Rossby waves south of the equatorial Indian Ocean (IO), which could exert a great influence on the subsequent South and East Asian summer monsoons. This brings the seasonal predictability to the regional monsoons. Here we identify a strengthening effect of El Nino on the following spring SWIO warming during 1948-2020. This is owing to the enhancing intensity and lengthening duration of the El Nino-related warm sea surface temperature anomalies over the tropical central Pacific in recent decades. In particular, this strengthening lagged effect of El Nino on the SWIO warming further results in more significant correlations between El Nino and the subsequent South and East Asian summer monsoons. Conceivably, this enhances the regional monsoon predictability, with potentially tremendous benefits for the socio-economic livelihood of billions of people living in the Asian monsoons.