The predictability limit of the amplitude and phase of the Madden‐Julian oscillation

• Main Authors: Deyu Lu, Ruiqiang Ding, Jianping Li
• Format: Article
• Language: English
• Published: Wiley 2020-06-01
• Series: Atmospheric Science Letters
• Subjects: amplitude; Madden–Julian oscillation (MJO); phase; predictability; the nonlinear local Lyapunov exponent (NLLE)
• Online Access: https://doi.org/10.1002/asl.968

Abstract The Madden–Julian Oscillation (MJO) is characterized by slowly eastward‐propagating precipitation and circulation anomalies with time scales of about 30–80 days. Both the phase and amplitude of the MJO fluctuate with time as it propagates eastward. Despite recent progress in understanding the predictability limit of the MJO as a whole, little is known of the difference in the predictability limits of its amplitude and phase. This paper investigates these differences using the nonlinear local Lyapunov exponent approach, which provides an estimate of atmospheric predictability based on observational data. The predictability limit of the phase of the MJO is determined as ~32 days, which is higher than that of its amplitude (about 16 days). In state‐of‐the‐art operational forecast models, the phase of the MJO is also found to have a much better forecast skill than does its amplitude. The relatively low limit of the predictability of the amplitude will pose a challenge to MJO prediction.