Variability of the MJO in the NCEP Climate Forecast System Reanalysis and Reforecasts

The Madden Julian Oscillation (MJO) is an eastward propagating intraseasonal mode of tropical coupled ocean-atmosphere variability that has significant impacts on the evolution of tropical and extratropical climate variations. Accurate assessment and simulation of the MJO and its related climate impacts are thus a necessary goal for improving subseasonal to seasonal climate predictions. Although simulating the MJO has historically proven to be an onerous burden for climate models, recent advances have been achieved in many climate modeling systems.

Features of the MJO are analyzed in observational datasets and the NCEP Climate Forecast System Reanalysis and Reforecasts (CFSRR). This brand new state-of-the-art coupled reanalysis and reforecast system includes numerous model and data assimilation upgrades over its predecessors (R1, R2, and CFS version 1), offering prospects for improved understanding and simulation of the MJO, especially given that much of the MJO fluctuations occur over the sparsely observed tropical Indian Ocean. The analysis leans on internationally accepted diagnostic techniques to assess the fidelity of MJO simulations and predictions in the NCEP CFS versions 1 and 2, and includes intermodel comparisons, case study analysis, and sensitivity of MJO characteristics to varying ENSO phases.