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Foundation ::
Meteorological Applications ::
GRAM-95
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GRAM-95
NASA/MSFC Global Reference Atmospheric Model-1995
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SOURCE CODE AVAILABLE
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The NASA/MSFC Global Reference Atmospheric Model was developed in response to the need for a design reference atmosphere that provides complete global geographical variability and complete altitude coverage (surface to orbital altitudes) as well as complete seasonal and monthly variability of the thermodynamic variables and wind components. A unique feature of GRAM95 is that, in addition to providing the geographical, height and monthly variation of the mean atmospheric state, it includes the ability to simulate spatial and temporal perturbations in these atmospheric parameters (e.g., fluctuations due to turbulence and other atmospheric perturbation phenomena).
As with earlier versions, GRAM-95 provides complete geographical and altitude coverage for each month of the year. Individual years 1985 to 1991 and a period-of-record (1980 to 1991) can be simulated for the Global Upper Air Climatic Atlas (GUACA) height range (0 to 27 km). GRAM-95 uses a specifically developed data set, based on Middle Atmosphere Program (MAP) data, for the 20 to 120 km height range, and the NASA Marshall Engineering Thermosphere (MET) model for heights above 90 km. Fairing techniques assure a smooth transition in the overlap height ranges (20 to 27 km and 90 to 120 km).
In addition to the traditional GRAM variables of pressure, density, temperature and wind components, GRAM-95 now includes water vapor and 11 other atmospheric constituents. A new, variable-scale perturbation model provides both large-scale and small-scale deviations from mean values for the thermodynamic variables and horizontal and vertical wind components. The perturbation model includes new features that simulate intermittency ("patchiness") in turbulence and small scale perturbation fields. The density perturbations and density gradients (density shears) computed by the new model compare favorably in their statistical characteristics with observed density perturbations and density shears from 32 space shuttle reentry profiles. GRAM-95 provides considerable improvement in wind estimates from the new GUACA data set, compared to winds calculated from the geostrophic wind relations previously used in the 0 to 25 km height range.
GRAM-95 carries the NASA case number MFS-31105. It was originally released as part of the NASA COSMIC collection.
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