AirWare On-line Reference Manual
| ||Release Level || 7.0 |
| ||Revision Level ||beta|
| ||Release Date ||2015 03 |
DWM: A Diagnostic Multi-layer Wind Model
One of the most important elements of any atmospheric simulation system is
the computation of a realistic wind field in a complex terrain.
The Diagnostic Wind Model (DWM, Douglas 1990)
generates quasi steady-state gridded wind fields for each set
of input conditions.
It adjusts the domain-scale mean wind for terrain effects
(kinematic effects like lifting and acceleration of the
airflow over terrain obstacles as well as thermodynamically
generated slope flows). It performs a
divergence minimization to ensure mass conservation.
The model can use one or more meteorological stations the user can select
in the meteorological scenario
Vertical and horizontal structure
DWM uses a number of vertical layers; these are consistent with the
vertical structure in CAMx and its meteo scenario.
If MM5 is used as a meteorological pre-processor,
these layer definitions are used to
generated the required vertical structure by the MM5
post-processor that generates the CAMx input files.
The horizontal resolution of the computational grid is set to 1,000 m.
Vertical layers (in meters)
| 0 || - ||25
| 25 || - ||50
| 50 || - ||100
| 100 || - ||200
| 200 || - ||500
| 500 || - ||1000
| 1000 || - ||2000
| 2000 || - ||4000
The following steps are performed in the DWM calculations:
The model output is a terrain and atmospheric stability-adjusted 3D wind field with
its appropriate stability parameters.
STEP 0: selection of the appropriate parametrization for the given meteorological
STEP 1: construction of an inert vertical wind profile depending on atmospheric
stability and determination of a set of stability parameters (Ermak 1991).
STEP 2: parametrization of kinematic terrain effects (Liu 1980).
STEP 3: intermediate divergence minimization to adjust the horizontal wind
components in each vertical level (Goodin 1980).
STEP 4: computation of thermodynamically generated slope flows, modifies the
horizontal surface wind components (Allwine 1985).
STEP 5: Froude number adjustment for the horizontal wind (Allwine 1985).
STEP 6: smoothing of the horizontal wind field.
STEP 7: divergence computation of the horizontal field, new vertical wind
STEP 8: vertical adjustment of the vertical wind (zero at the top or at the mixing h
eight) (O'Brien 1970).
STEP 9: final divergence minimization to adjust the horizontal wind ->
final wind field.
Allwine K.J., Whiteman C.D. (1985)
- MELSAR: A Mesoscale Air Quality Model for
Complex Terrain: Volume 1 - Overview, Technical Description and Users Guide. Pacific
Northwest Laboratory, Richland (PNL-5460).
Ermak L.D. (1991)
- User's Manual for SLAB: An Atmospheric Dispersion Model for
Denser-Than-Air Releases. National Technical Information Services (NTIS), DE91-
008443, Springfield, VA.
Douglas G.S., Kessler R.C., Carr L. (1990)
- User's Manual for the Diagnostic Wind
O'Brien J.J. (1970)
- Alternative solutions to the classical vertical velocity profile. J.
Applied Meteorol., 9: 197-203.