Potential predictability of the MJO during easterly and westerly phases of the QBO

Abstract

The potential predictability of the Madden-Julian Oscillation (MJO) in boreal winter (November-February) is investigated using observational data for the period of 1979-2016. For various MJO indices, nonlinear local Lyapunov exponents are computed to quantify the MJO predictability under the easterly and westerly phases of the Quasi-Biennial Oscillation (easterly: EQBO and westerly: WQBO). All MJO indices exhibit higher predictability during EQBO winters than during WQBO winters. Excluding strong ENSO years from EQBO and WQBO winters has a limited impact on MJO predictability. The highest potential predictability of 43 days during EQBO winters and 37 days during WQBO winters is found for the MJO index obtained from bandpass-filtered (30-80 days) outgoing longwave radiation and wind data. In contrast, the potential predictability of the MJO from the real-time multivariate MJO index is 21 days during EQBO winters and 13 days during WQBO winters. The longer persistence and less disorganization of the MJO during the EQBO winters lead to the higher predictability for EQBO winters, as compared with that for WQBO winters.