Impact of the quasi-biennial oscillation on predictability of the Madden-Julian oscillation

Abstract

The Madden-Julian oscillation (MJO) during boreal winter is observed to be stronger during the easterly phase of the quasi-biennial oscillation (QBO) than during the westerly phase, with the QBO zonal wind at 50 hPa leading enhanced MJO activity by about 1 month. Using 30 years of retrospective forecasts from the POAMA coupled model forecast system, we show that this strengthened MJO activity during the easterly QBO phase translates to improved prediction of the MJO and its convective anomalies across the tropical Indo-Pacific region by about 8 days lead time relative to that during westerly QBO phases. These improvements in forecast skill result not just from the fact that forecasts initialized with stronger MJO events, such as occurs during QBO easterly phases, have greater skill, but also from the more persistent behaviour of the MJO for a similar initial amplitude during QBO easterly phases as compared to QBO westerly phases. The QBO is thus an untapped source of subseasonal predictability that can provide a window of opportunity for improved prediction of global climate.