[A-CG31] Climate Variability and Predictability on Subseasonal to Centennial Timescales

[ACG31-06] Change in MJO predictability by the Indo-Pacific Warm Pool Expansion

★Invited Papers

*Hyemi Kim¹ (1.Ewha Womans Univ.)

Keywords:MJO, predictability, warm pool expansion, future projection

The characteristics of the Madden-Julian oscillation (MJO), a dominant mode of tropical intraseasonal variability, have changed and is projected to change by the expansion of the Indo-Pacific warm-pool which is the Earth's largest region of warm sea surface temperatures (SSTs). However, the likelihood of the MJO predictability change following the warm-pool expansion has not been addressed. In this study, the effect of warm-pool expansion on MJO variability and predictability is investigated with highly idealized aqua-planet configuration of CESM2. By expanding the warm-pool in the Indo-Pacific, the MJO-like wave becomes more regionally confined short-lived convective events with weaker magnitude and less robust eastward propagating signal, possible due to stronger zonal SST gradient and wider meridional width of the warm pool in idealized warm-pool simulations. By performing a perfect-model ensemble experiments, it is shown that the MJO predictability reduces about 5-days, and forecast error increases faster while signal reduced faster when the warm-pool is expanded. The implication of this study relevant to the science community is that if the warm-pool keeps to expand in the future, MJO is likely to become less organized, regionally confined, and having a shorter period, which altogether contributes to its predictability loss.