Control of gravitational oscillations in variational data assimilation
- Florida State Univ., Tallahassee (United States)
- NOAA, Washington, DC (United States)
Variational four-dimensional data assimilation was combined with a penalty method constraining time derivatives of the surface pressure, the divergence, and the gravity-wave components for use on an adiabatic version of the National Meteorological Center's 18-level primitive equation spectral model with surface drag and horizontal diffusion. Experiments combining the Machenhauer nonlinear normal-mode initialization procedure and its adjoint with the variational data assimilation are presented. The modified variational data-assimilation schemes were tested to assess their effectiveness in controlling gravity-wave oscillations. The gradient of a penalized cost function could be obtained by a single integration of the adjoint model. A detailed derivation of the gradient calculation of different penalized cost function is presented. The numerical results indicate that the inclusion of penalty terms into the cost function would alter the model solution as desired. The advantage of using simple penalty terms rather than using penalty terms including the model normal modes is that it results in a simplification of the procedure, allowing for more direct control over variables and the possibility of using weak constraints to eliminate high-frequency gravity wave oscillations. The approach does not require direct inforamtion concerning the model normal modes. 21 refs., 19 figs.
- OSTI ID:
- 6624686
- Journal Information:
- Monthly Weather Review; (United States), Journal Name: Monthly Weather Review; (United States) Vol. 121:1; ISSN MWREAB; ISSN 0027-0644
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
540110*
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
ADIABATIC PROCESSES
ALGORITHMS
CALCULATION METHODS
COMPUTER CALCULATIONS
CONSTRAINTS
COST
DATA ANALYSIS
DIFFUSION
DRAG
FOUR-DIMENSIONAL CALCULATIONS
GENERAL CIRCULATION MODELS
GRAVITY WAVES
ITERATIVE METHODS
MATHEMATICAL LOGIC
MATHEMATICAL MODELS
OSCILLATIONS