Regional Model Studies of the Madden and Julian Oscillation

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The project will advance the understanding and modeling of Madden-Julian Oscillation (MJO) variability in the tropics from numerical experiments with a regional model and coordinated diagnostic studies. The experiments are designed to test various hypotheses for MJO genesis, particularly those related to internal mechanisms and specific boundary forcing. The focus will be on initiation and development of intra-seasonal convection over the equatorial Indian and western Pacific ocean basins. Drs. Weare and Chen (University of California, Davis) will conduct a suite of numerical experiments with regional models (MM5, WRF) in which boundary conditions can be manipulated to selectively suppress one or more of the hypothesized mechanisms. The PIs expect comparisons of "control" and "perturbed" simulations of 20-70 day variability to reveal the dominant mechanism of MJO development in both normal and ENSO climate conditions. Simulation of MJO variability poses a great challenge: The state-of-the-art atmospheric GCMs and coupled climate models (e.g., NCAR's Community Atmospheric Model and Community Climate System Model) are presently unable to simulate this phenomenon and its tropical and midlatitude impacts. The project will thus lead to greater understanding and, potentially, more accurate modeling of MJO variability, and its influence on long-term weather and seasonal-to-interannual climate variability.