Asymmetric Response of Predictability of East Asian Summer Monsoon to ENSO

Abstract

The connection between the predictability of the East Asian summer monsoon (EASM) and El Niño-Southern Oscillation (ENSO) has recently attracted widespread attention. Of particular importance is the effect of El Niño and La Niña on EASM predictability. In this paper, the signal-to-noise ratio (SNR) method is used to analyze reanalysis data, and the results show that the EASM potential predictability intensity is much stronger under El Niño forcing than that under La Niña forcing. Meanwhile, the asymmetric response of EASM predictability remains within the Community Atmosphere Model (CAM) simulations. The EASM predictability is quantitatively determined using the nonlinear local Lyapunov exponent (NLLE) method. The EASM predictability limit under El Niño forcing is longer than that for La Niña forcing. Two monsoon indices are used to measure the EASM, the predictability limits of which perform differently because of their particular definitions. However, the asymmetric response of EASM predictability to El Niño and La Niña can be verified using observational data and model experiments.