AirWare On-line Reference Manual
| | Release Level | 5.4 |
| | Release Date | 2008 10 |
| Revision Level | 1.0 |
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Last modified on:
Monday, 20-Jul-09 14:03 CEST
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CAMX: meteorological input data
CAMx reads and writes several 3-D time resolved files that will
require significant disk space. Therefore, these files are written as Fortran unformatted binary
to minimize storage requirements.
In contrast to the usual CAMx input files written in the IEEE "big_endian",
for AIRWARE the IEEE "little_endian" has to be used for compatibility reasons.
A detailed description of the file formats required can be found in the CAMx User's Guide,
Version 4.30, Environ International Corporation, Novato, CA, 2006, pp.5.30 - 5.34.
CAMxUsersGuide_v4.30.pdf
Main input files
- Height/Pressure File:
The Fortran binary height/pressure input file contains three-dimensional
gridded fields of layer interface heights and layer-average pressure.
- Wind File:
The Fortran binary wind file contains three-dimensional gridded fields
of layer average horizontal (u and v) wind components.
- Temperature File:
The Fortran binary temperature file contains three-dimensional gridded
fields of layer average temperature and two-dimensional gridded fields
of surface temperature.
- Water Vapor File:
The Fortran binary water vapor file contains three-dimensional gridded
fields of layer average water vapor concentration.
- Cloud/Rain File:
The Fortran binary cloud/rain file contains three-dimensional gridded
fields of cloud parameters to be used for chemistry and wet/dry deposition
calculations. Note that precipitation rate is not explicitly provided to
the model; instead, it is internally calculated from the three precipitation
water content forms provided on the cloud/rain file.
- Vertical Diffusivity File:
The Fortran binary vertical diffusivity file contains three-dimensional
gridded fields of layerinterface
vertical diffusivity (i.e., turbulent exchange or diffusion coefficients).
CAMx can use the (optional)MM5 meteorological pre-processor to
generate all necessary meteorological input files.
If no MM5 meteorological pre-processor output is available,
meteorological data are derived in the following way:
- Height/Pressure File:
Layer interface heights are fixed at
25 m, 50 m, 100 m, 200 m, 500 m, 1000 m, 2000 m and 4000 m.
Pressure (mb) [time variant 3-dim matrix]
calculated from ground atmosheric pressure and temperature and elevation
M = 0.028964; [kgmol-1] molweight of air
g = 9.81; [ms-2] acceleration due to gravity
R = 8.314; [JK-1mol-1] Gas Constant
h: height
t[i][j] temperature of grid cell i,j, h=0
pres[i][j] pressure of grid cell i,j, h=0
p[(i,j,h) pressure of grid cell i,j, h
p[(i,j,h) = pres[i][j] * exp((-M*g*h/(R*t[i][j])));
Since most monitoring stations do not contain values for pressure,
pres[i][j] = 1001 mb at h = 0 m is assumed for all i, j of the domain
- Wind File
The 3D wind dynamic field is calculated using the Diagnostic Wind Field Model
DWM and a synthetic geostrophic wind
(assumed to be homogeneous over the domain) estimated from
the (vector average) of anemometric wind data, using an exponential vertical profile
for speed and a Coriolis induced rotation.
This is based on the DEM ( 1 km resolution) for the domain, and the
anemometric wind speed and wind direction of one or more monitoring stations
the user can select interactively for the
meteo scenarios for scenario analysis
(AERMOD and CAMx). The station selection for nowcast and forecast runs are configurable
but not interactively to better maintain consistency.
- Temperature File
Temperature [time variant 3-dim matrix] is
calculated from ground temperature [2-dim matrix] and height,
assuming adiabatic lapse rate alr =0.003 K/m
h: height (elevation + layer height)
T(x,y,h)* = T(x,y,h=0) - alr*h
The temperature of the selected monitoring station is the basis of the calculation.
Surface Temperature [time variant 2-dim matrix]
The temperature of the selected monitoring station is the basis of the calculation.
- Water Vapor File
Water vapor concentration (ppm) [time variant 3-dim matrix]
calculated from temperature, pressure and relative air moisture
(Clausius-Clapeyeron, assuming temperature independent enthalpy)
R = 8.314 JK-1mol-1 gas constant
TR = 273.15 K reference temperature
H = 45050 Jmol-1 molar enthalpy of evaporation at TR
PR = 611 Pa saturated partial pressure of water vapor at TR
M_H2O = 18 gmol-1 molecular weight of water
M_AIR = 29 gmol-1 molecular weight of air
f = 0.4 assumed relative humidity
ps: saturated partial pressure of water vapor
ph2o: partial pressure of water vapor
t: temperature of grid cell i,j
pg: (total) pressure of grid cell i,j
w: absolute humidity of grid cell i,j
ps = PR*exp( -(H/R)*((1/t) - (1/TR)) );
ph2o = f*ps;
w = (M_H2O/M_AIR)*(ph2o/(pg-ph2o));
no data a re available: relative air moisture
is set to 40% for the whole domain.
- Cloud/Rain File
no data available: set to zero.
- Vertical Diffusivity File
Vertical diffusivity (m2/s) [time variant 3-dim matrix] is
calculated from surface roughness, the temporal temperature gradient
and layer height:
vd(i,j) = 10*sqrt(rough(i,j))*(t(i,j) - t_min(i,j) + 1)*(exp(cc*h))
vd(i,j): vertical diffusivity (m2/s) of grid cell i,j
rough(i,j): surface roughness of landuse categorie of grid cell i,j
t(i,j): temperature of grid cell i,j
t_min(i,j): minimal temperature of the day of grid cell i,j
h: layer height
cc = -0.004 exponential factor
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