Delineating the Seasonally Modulated Nonlinear Feedback Onto ENSO From Tropical Instability Waves

Aoyun Xue , Fei-Fei Jin , Wenjun Zhang , Julien Boucharel (1) , Sen Zhao , Xinyi Yuan

1 LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales

Tropical instability waves (TIWs), the dominant form of eddy variability in the tropics, have a peak period at about 5 weeks and are strongly modulated by both the seasonal cycle and El Niño-Southern Oscillation (ENSO). In this study, we first demonstrated that TIW-induced nonlinear dynamical heating (NDH) is basically proportional to the TIW amplitude depicted by a complex index for TIW. We further delineated that this NDH, capturing the seasonally modulated nonlinear feedback of TIW activity onto ENSO, is well approximated by a theoretical formulation derived analytically from a simple linear stochastic model for the TIW index. The results of this study may be useful for the climate community to evaluate and understand the TIW-ENSO multiscale interaction.

Keywords: ENSO; tropical instability waves; NDH; combination tone; rectification effects; nonlinear feedback

Domains: Sciences of the Universe [physics]; Earth Sciences

Aoyun Xue, Fei-Fei Jin, Wenjun Zhang, Julien Boucharel, Sen Zhao, et al.. Delineating the Seasonally Modulated Nonlinear Feedback Onto ENSO From Tropical Instability Waves. Geophysical Research Letters, 2020, 47, ⟨10.1029/2019GL085863⟩. ⟨insu-03671099⟩