The Madden–Julian Oscillation and Its Impact on Northern Hemisphere Weather Predictability

The Madden–Julian oscillation (MJO) is known as the dominant mode of tropical intraseasonal variability and has an important role in the coupled-atmosphere system. This study uses numerical model experiments to investigate the influence of the MJO activity on weather predictability in the midlatitudes of the Northern Hemisphere. The National Aeronautics and Space Administration (NASA) Goddard Laboratory for the Atmospheres (GLA) general circulation model was used in a 10-yr simulation with fixed climatological SSTs to generate a control dataset as well as to select initial conditions for active MJO periods and “Null” cases. Two perturbation numerical experiments were performed for the 75 cases selected [(4 MJO phases + Null phase) × 15 initial conditions in each]. For each alternative initial condition, the model was integrated for 90 days. Mean anomaly correlations and standardized root-mean-square errors in the midlatitudes of the Northern Hemisphere (20°–60°N) were computed to assess predictab...