Equatorial Submesoscale Eddies Contribute to the Asymmetry in ENSO Amplitude

El Nino/Southern Oscillation (ENSO) exhibits evident amplitude asymmetry with stronger El Nino than La Nina events. Equatorial submesoscale eddies act as an important damper of ENSO via their induced upward heat flux (Qeddy,vsub ${Q}_{\mathrm{e}\mathrm{d}\mathrm{d}\mathrm{y},v}<^>{\mathrm{s}\mathrm{u}\mathrm{b}}$) from the subsurface to the surface ocean. Yet their effect on ENSO amplitude asymmetry remains unexplored. Using a high-resolution global climate simulation, we found that strengthening of Qeddy,vsub ${Q}_{\mathrm{e}\mathrm{d}\mathrm{d}\mathrm{y},v}<^>{\mathrm{s}\mathrm{u}\mathrm{b}}$ in the Nino3.4 region during La Nina is more evident than weakening of Qeddy,vsub ${Q}_{\mathrm{e}\mathrm{d}\mathrm{d}\mathrm{y},v}<^>{\mathrm{s}\mathrm{u}\mathrm{b}}$ during El Nino, resulting in stronger damping of La Nina than El Nino events. This asymmetric response of Qeddy,vsub ${Q}_{\mathrm{e}\mathrm{d}\mathrm{d}\mathrm{y},v}<^>{\mathrm{s}\mathrm{u}\mathrm{b}}$ to ENSO is primarily ascribed to that of the temperature fronts associated with larger-scale processes. Using a recharge oscillator model modified to include the effects of Qeddy,vsub ${Q}_{\mathrm{e}\mathrm{d}\mathrm{d}\mathrm{y},v}<^>{\mathrm{s}\mathrm{u}\mathrm{b}}$, we show that the asymmetric damping of ENSO by Qeddy,vsub ${Q}_{\mathrm{e}\mathrm{d}\mathrm{d}\mathrm{y},v}<^>{\mathrm{s}\mathrm{u}\mathrm{b}}$ contributes importantly to the ENSO amplitude asymmetry.