A sensitivity study of the Kelvin wave and Madden-Julian Oscillation in aquaplanet simulations by the Naval Research Laboratory spectral element atmospheric model
Kim, Y.-J., F. X. Giraldo, M. Flatau, C.-S. Liou, and M. S. Peng
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The dynamical core of the Naval Research Laboratory (NRL) Spectral Element Atmospheric Model (NSEAM) is coupled with full physics and used to investigate the organization and propagation of equatorial atmospheric waves under the aquaplanet conditions. The sensitivity of the model simulation to the amount of horizontal viscosity, distribution of the vertical levels, and selected details of the precipitation physics is examined and discussed mainly utilizing simulated convective precipitation with the aid of time-longitude plots and the spectral diagrams designed by Wheeler and Kiladis (1999). It is shown that the simulation of the Kelvin wave and Madden-Julian Oscillation depends strongly on the details of the vertical level distribution and the choice of parameters in the convective parameterization. Efforts are made to calibrate the new model to capture the essential interaction between the dynamics and physics of the atmosphere. The speed and spectrum of the eastward propagating Kelvin waves and the signature of the Madden-Julian Oscillation simulated by the new model reveal main features similar to those predicted by the simplified theory and found in limited observations. This study attempts to understand the significant variability found among the aquaplanet simulations by various global atmospheric models and highlights the uncertainties concerning convective processes and their coupling to large-scale wave motion in large-scale models of the atmosphere.
Non-hydrostatic Unified Model of the Atmosphere (NUMA)The precursor to NUMA was the Navy’s Spectral Element Atmospheric Model (NSEAM). NSEAM is a complete atmospheric model with all the necessary sub-grid scale parameterizations and real orography. NSEAM is a hydrostatic global atmospheric model that uses surface pressure, momentum, and potential temperature for its prognostic variables; spectral elements are used in the horizontal and centered finite differences in the vertical; the model uses explicit, semi-implicit BDF2 and LF2 time-integrators; is fully MPI capable; and has been used for idealized dry dynamics tests as well as more realistic aquaplanet simulations.
RightsThis publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
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Kelvin Wave and Madden-Julian Oscillation Simulated by A Spectral Element Atmospheric Model under Aqua-Planet Conditions Kim, Young-Joon; Giraldo, Francis X.; Flatau, Maria; Liou, Chi-Sann; Peng, Melinda S. (2008-12);The Naval Research Laboratory (NRL) Spectral Element Atmospheric Model (NSEAM) coupled with full physics is used to investigate the organization and propagation of Kelvin waves and Madden-Julian Oscillation under the ...
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