Different Impacts From Various El Ni?o Events To Wyrtki Jets At Boreal Fall Season

TheEl Ni?o event is the significant air-sea interaction phenomenon over the tropical Pacific,which plays important roles on the global climate change.Previous studies pointed out El Ni?o events are able to be classified as Canonical El Ni?o,El Ni?o Modoki I and El Ni?o Modoki II based on the various temporal and spatial distributions of sea surface temperature anomaly over tropical Pacific region.This research reveals that different types of El Ni?o events present distinct effect on the variation of Wyrtki jets over the tropical Indian Ocean at boreal fall season.The autumn Wyrtki jets of the Indian Ocean are significantly weakened during the Canonical El Ni?o event.While,during the El Ni?o Modoki I and II events,the Wyrtki jets are stronger than the historical average.Further analysis illustrates the anomalous Walker circulation over the in the Indo-Pacific region modulated by different types of El Ni?o events is responsible for the variation of Wyrtki jets.Since WJ modulate the surface salinity transportationfrom eastern Indian Ocean to western Indian Ocean,vise vesa,this research performed the analysis on the salinity budget in the Indian Ocean during different El Ni?o periods.The research identified that the zonal advection play dominant roles on the salinity varaition over the central Indian Ocean.During the classic El Ni?o period,the salinity anomalies over the central Indian Ocean decreased continuly,while in the El Nino Modoki I and II period,the anomalously WJs induced thestrengthen of salinity anomalies over the central Indian Ocean.This study assessed simulations of 15 CMIP5 models that simulated the fall WJ under the influence from different types of El Ni?o events.The results show that the CMIP5 modelsare able to reproduce the anomalous westward flow over the tropical Indian Ocean during the canonical El Ni?o period,while the simulation of WJ during the autumn of the El Nino Modoki period is limited.