Changes in Madden-Julian Oscillation Activity and Easterly Waves in a Warmer Climate

Easterly waves (EWs), are one of the precursors to tropical storms, which are among the deadliest and costliest weather phenomena due to their coastal hazards. EWs are synoptic-scale disturbances associated with intense cyclonic vorticity and surface wind convergence, cloudiness, and heavy precipitation. Other disturbances, such as the Madden-Julian Oscillation (MJO), make conditions favorable for hurricane spin-up by creating periods of anomalous westerly winds that are associated with enhanced cyclonic flow, moisture, precipitation, and EW activity. Wind and precipitation anomalies can be tracked across eight MJO phases ranging from its initiation over the Indian Ocean to decay over the central Pacific. The MJO is expected to become stronger in a warmer environment, which could cause its modulation of EWs to become stronger with increased effects on vulnerable communities. Research for vulnerable communities to prepare for climate change and its uncertainties associated with MJO and EWs is needed. This investigation uses the CESM2 Large Ensemble to examine the frequency and intensity of EWs and their modulation by the MJO. This study examines how the frequency and intensity of EWs will change in a future (warmer) climate, including whether their relationship to MJO activity changes. The investigation analyzes data during boreal summer–the peak of EW activity and predictability. The results highlight EW suppression and intensification is stratified by MJO phase. Initial results suggest a general decrease in EW activity across the tropics with warming. As future climate change can amplify the risk to life and property along vulnerable coastlines, the results demonstrate how the MJO can offer a lens into those changes and new pathways toward improved predictability.