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Model Description |
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Model Description |
The NRL Mountain Wave Forecast Model (MWFM) was
written and developed by Dr. Julio Bacmeister. It uses a simple two-dimensional
hydrostatic gravity wave model and meteorological model forecasts of wind and
temperature to generate a forecast of mountain wave activity. The key to producing this
forecast is a detailed representation of global topography, which includes estimates of
the locations, widths, heights and orientations of nearly all mountain ridges on Earth
with scales ranging from a hundred kilometers down to several kilometers.
This ridge database is compiled from 5'x5' digital elevation data using objective techniques to identify significant features. This approach appears to do a reasonable job of forecasting mountain wave amplitudes in the upper troposphere and lower stratosphere [Bacmeister et al. 1994]. Efforts are currently underway to validate the approach in the lower atmosphere. Mountain wave forecasts for the U.S.A. using the latest available 12, 36 or 60 hour forecast model output from the National Center for Environmental Prediction (NCEP) are made daily and are posted on our web site. An advantage of the simple model like MWFM (see Figure 1) is that global climatologies of mountain wave activity can be quickly compiled. While the climatologies may not be correct in detail, the gross overall picture of global mountain waves derived from this approach should be basically correct. We have performed such calculations using a variety of ridge databases and simple wave models. A consistent feature of these calculations is the extremely strong mountain wave activity in the stratosphere in winter over Scandinavia. The presence of this activity is anecdotally verified by frequent sightings of ``nacreous'' clouds (irridescent, high-alititude ice clouds which resemble mother-of-pearl) over Norway. REFERENCES
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