| dc.description.abstract | Over the past few decades, El Niño Modoki has been revealed to be distinguished from the canonical El Niño in terms of the El Niño Modoki index. Based on the rainfall patterns in southern China (Wang and Wang, 2013), El Niño Modoki events can be further divided into two types. In El Niño Modoki I, positive sea surface temperature anomaly (SSTA) first emerges in the central equatorial Pacific during spring, develops over the same region, and then damps quickly in the summer of the second year. In El Niño Modoki II, the positive SSTA first appears in the northeastern subtropical Pacific in spring, and then develops toward the equatorial central Pacific. The warm SSTA persists into the second year and slowly decays in the central Pacific during the subsequent seasons.
According to Chen et al. (2021), the recharge oscillator mechanism tends to produce a cyclic transition in the evolution of El Niño. Nevertheless, our results show that El Niño Modoki I features a strong La Nina-like SSTA pattern in the decaying phase with a relatively weaker recharge-discharge process compared to El Niño Modoki II. To clarify the factors except for the recharge oscillator that differs the development process of two types of El Niño Modoki, a mixed layer heat budget analysis is further conducted. In El Niño Modoki I, the easterly wind anomalies appear during the decaying phase, releasing heat from the ocean and resulting in negative latent heat anomalies. Through strong Bjerknes feedback, winds are able to develop continually and cool the eastern Pacific quickly. On the other hand, in El Niño Modoki II, the wind-evaporation-SST (WES) feedback continually provides a positive effect, sustaining warm SSTA in the central Pacific during the entire evolutionary process.
To further explore the dynamics of El Niño Modoki under global warming, CAMS-CSM1-0 was selected from the 15 of CMIP6 models through the Taylor diagram as it can best distinguish the unique patterns of different types of El Niño in the historical simulations. The model does a good job on characterizing the different SSTA patterns during the mature phase between the two types of El Niño Modoki, particularly in the subtropical Pacific. | en_US |