Adiabatic and Diabatic Initialization of the AFGL (Air Force Geophysics Laboratory) Global Spectral Model Using Dynamic Normal Mode and Nonlinear Normal Mode Methods
Final rept. Oct 1987-Sep 1988
AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA
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Dynamic normal mode initialization DNI is applied to low and high resolution versions of the AFGL global spectral mode. This scheme is tested against the operational nonlinear normal mode initialization NMI procedure using both adiabatic and diabatic forms of the model tendencies. The DNI-based forecasts are comparable in accuracy to the NMI-based forecasts, with small differences between the adiabatic and diabatic versions of each. DNI initial conditions were somewhat more damped in the divergence fields than were the NMI fields. This is believed to be due to the frequency response characteristics of the DNIs forward-backward time scheme, which tended to partially damp resolvable wavelengths. Keywords Numerical weather predictions, Spectral atmospheric models, Weather forecasting, Normal modes, Global model initialization, Diabatic initialization.