Resilience of an Explicitly Simulated Madden-Julian Oscillation to Extreme Basic State Variation Challenges Moisture Mode View

Wednesday, December 16, 2015 - 14:55
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Idealized experiments are performed with the SuperParamaterized CAM to test two hypotheses motivated by a modern view of the “moisture mode” theory of the Madden Julian Oscillation. Inconsistent with both hypotheses, evidence is found of a cold-MJO signal under horizontally homogenous SSTs. Apparently the intrinsic MJO signal in SPCAM3 is a surprisingly resilient mode that can survive both extreme cooling of the climate and a reversal of near-equatorial meridional MSE gradients. Column MSE analysis indicates a negative overall growth rate of MJO MSE in our coldest simulations, which is hard to reconcile with the survival of a cold MJO from a moisture mode view. A resilience of familiar features of the MJO-MSE budget in our simulations could indicate some other cause, beyond local column MSE dynamics, requires such phase relationships to exist.