MJO ensemble prediction in BCC-CSM1.1(m) using different initialization schemes

The Madden-Julian Oscillation (MJO) is a dominant mode of tropical intraseasonal variability (ISV) and has prominent impacts on the climate of the tropics and extratropics. Predicting the MJO using fully coupled climate system models is an interesting and important topic. This paper reports upon a recent progress in MJO ensemble prediction using the climate system model of the Beijing Climate Center, BCC-CSM1.1(m); specifically, the development of three different initialization schemes in the BCC ISV/MJO prediction system, IMPRESS. Three sets of 10-yr hindcasts were separately conducted with the three initialization schemes. The results showed that the IMPRESS is able to usefully predict the MJO, but is sensitive to the initialization scheme used and becomes better with the initialization of moisture. In addition, a new ensemble approach was developed by averaging the predictions generated from the different initialization schemes, helping to address the uncertainty in the initial values of the MJO. The ensemble-mean MJO prediction showed significant improvement, with a valid prediction length of about 20 days in terms of the different criteria, i.e., a correlation score beyond 0.5, a RMSE lower than 1.414, or a mean square skill score beyond 0. This study indicates that utilizing the different initialization schemes of this climate model may be an efficient approach when forming ensemble predictions of the MJO.