Abstract:The study uses monthly sea surface temperature (SST) data from HadISST, monthly SST and three-dimensional ocean current velocity assimilation data from SODAv2.2.4, and monthly surface air temperature (SAT) at 2 m from NCEP/NCAR during 1950-2020 in winter. Combined with the asymmetric composite difference analysis method and mixed layer heat budget analysis method, the possible ocean dynamic processes of significantly asymmetric SST anomaly over the eastern (E region: 110°W-80°W, 10°S-10°N) and central (C region: 160°E-170°W, 10°S-10°N) equatorial Pacific under El Niño and La Niña events are explored. The asymmetric spatial responses of SAT anomaly at 2 m under asymmetric forcing of ENSO events are also analyzed. The results show that El Niño events are significantly stronger than La Niña events in the E region, while the C region is the opposite. The contribution of nonlinear dynamic heating to the asymmetric components of SST anomaly in El Niño and La Niña years over the E and C regions is positive feedback, and it is the dominant dynamic factor that causes the positive and negative asymmetric components of SST anomaly in these two regions. Ekman pumping is unfavorable for the formation of the positive asymmetric component of the SST anomaly in the E region, but favorable for the formation of the negative asymmetric component of the SST anomaly in the C region. The formation of the negative asymmetric component of SST anomaly in the C region is damped by the positive feedback of mean circulation, zonal advection, and thermocline feedback. The asymmetric distribution of SAT anomaly at 2 m is consistent with the asymmetric spatial distribution of SST anomaly. However, the significant range of positive and negative asymmetric components of SAT anomaly is evidently reduced, and the asymmetric results in some areas are not significant.