High-latitude filtering in a global grid-point model using model normal modesA normal modes expansion technique is applied to perform high latitude filtering in the GLAS fourth order global shallow water model with orography. The maximum permissible time step in the solution code is controlled by the frequency of the fastest propagating mode, which can be a gravity wave. Numerical methods are defined for filtering the data to identify the number of gravity modes to be included in the computations in order to obtain the appropriate zonal wavenumbers. The performances of the model with and without the filter, and with a time tendency and a prognostic field filter are tested with simulations of the Northern Hemisphere winter. The normal modes expansion technique is shown to leave the Rossby modes intact and permit 3-5 day predictions, a range not possible with the other high-latitude filters.
Document ID
19870024439
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Takacs, L. L. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Kalnay, E. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Navon, I. M. (Council for Scientific and Industrial Research, National Research Institute for Mathematical Sciences, Pretoria Republic of South Africa, United States)