Improving MJO Forecasts in the Navy's Coupled Global Modeling System

Tuesday, 19 April 2016
Plaza Grand Ballroom (The Condado Hilton Plaza)
Carolyn A. Reynolds, NRL, Monterey, CA; and J. A. Ridout, M. K. Flatau, N. P. Barton, S. Yang, M. Janiga, and D. B. Baranowski

As part of the National Earth System Prediction Capability (National ESPC), the US Navy is developing the Navy Earth System Model (NESM), a fully coupled global system including the atmospheric Navy Global Environmental Model (NAVGEM), the HYbrid Coordinate Ocean Model (HYCOM), and the Los Alamos Sea Ice Model (CICE). One goal of this effort is the development a system capable of skillful monthly forecasts of the Madden-Julian Oscillation (MJO), given the importance of the MJO for extended-range prediction and its far-reaching impact on other phenomena. An overview of this effort, including the impact of coupling, observational studies, and physical parameterization improvements, will be presented. Specifically, it will be shown that while coupling of the atmosphere to the ocean improves aspects of the simulation, such as low-level wind biases, it is not sufficient to produce realistic MJO simulations. Improvements to the physical parameterizations in the atmospheric component of the NESM, primarily improvements to the convection scheme, result in substantial improvements in general precipitation patterns and the simulation of the MJO for monthly forecasts during the November 2011 Dynamics of the Madden-Julian Oscillation (DYNAMO) time period. While the physical parameterization improvements result in significantly better MJO simulations, they still exhibit excessively slow eastward propagation over the maritime continent. Observational diagnostics studies of TRMM precipitation indicate a phase-locking between Kelvin waves and the diurnal cycle of precipitation over the maritime continent. These results indicate that inaccuracies in the NESM diurnal cycle may be contributing to this excessive slowing of the MJO in that region.
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