Assessing Predictability and Prediction Skill of the MJO in ECMWF S2S Reforecast

by Shu-Yi Chen (Department of Atmospheric Sciences, U Washington)


The Madden-Julian Oscillation (MJO) has been recognized as a source of predictability of the global weather on the subseasonal-to-seasonal (S2S) time scales. However, the MJO initiation and eastward propagation of its the large-scale convection and precipitation over the Indo-Pacific warm pool remain to be difficult to evaluate quantitatively in NWP and climate models. This study aims to better understand the predictability and model prediction skill of the MJO using a new Large-scale Precipitation Tracking (LPT) method developed by Kerns and Chen (2016, 2020) based on the 20-year TRMM-GPM precipitation data and the ECMWF S2S reforecast from 1998-2018.  The advantage of LPT is its explicit representation of the MJO precipitation in terms of both zonal and meridional structure and variability in time and space. The S2S reforecast reproduced the observed MJO climatology in terms of the total number of the MJO events and seasonal variability very well. However, the timing and location of the MJO precipitation, especially over the tropical Indian Ocean, is less well predicted. In addition to the MJO, general characteristics of multiscale precipitation in the S2S reforecast compared with the TRMM-GPM observation will be discussed.