Table of Contents - The Atmospheric Studies Group at TRC

Section 1: Introduction
If the upper air wind speed, wind direction, or temperature is missing, CALMET will interpolate to
replace the missing data. Actually, the interpolation of wind data is performed with the u and v
components, so both the wind speed and direction must be present for either to be used. Because the
program does not extrapolate upper air data, the top valid level must be at or above the model domain and
the lowest (surface) level of the sounding must be valid.
For modeling applications involving overwater transport and dispersion, the CALMET boundary layer
model requires observations of the air-sea temperature difference, air temperature, relative humidity and
overwater mixing height (optional) at one or more observational sites. The model can accommodate
overwater data with arbitrary time resolution (e.g., sub-hourly, hourly, daily, or seasonal values). The
location of the overwater stations is allowed to vary in order to allow the use of observations made from
ships. CALMET optionally can use only land stations to calculate temperatures over land and only
overwater stations to calculate temperatures over water. If this option is used, vertical temperature lapse
rate information may be included at the overwater observational sites.
If the wet removal algorithm of the CALPUFF model is to be applied, CALMET can be made to produce
gridded fields of precipitation rates from precipitation observations. The routinely available NCDC
precipitation data in TD-3240 format or a free-formatted, user-prepared file of precipitation rates can be
used as input to CALMET.
CALMET also requires geophysical data including gridded fields of terrain elevations and land use
categories. Gridded fields of other geophysical parameters, if available, may be input to the model. The
optional inputs include surface roughness length, albedo, Bowen ratio, a soil heat flux parameter,
anthropogenic heat flux, and vegetation leaf area index. These parameters can be input as gridded fields
or specified as a function of land use. Default values relating the optional geophysical parameters to land
use categories are provided within CALMET.
As described in the previous section, CALMET contains an option to read as input gridded wind fields
produced by the prognostic wind field models. The CSUMM prognostic wind field model generates a file
called PROG.DAT which can be directly input into CALMET, or if using the MM4/MM5, NAM(Eta),
WRF, RUC, RAMS or TAPM derived data, a file called 3D.DAT (MM4.DAT is also accepted, but not
recommended) is required.
One of the options in CALMET is to by-pass the boundary layer model and compute only gridded wind
fields (i.e., produce U, V wind components only without the micro-meteorological variables such as
friction velocity, Monin-Obukhov length, etc.). Although the CALPUFF and CALGRID models cannot
be executed with such a file, there may be some applications in which only the wind components are of
interest. For example, a postprocessor (CAL2UAM) can be used to convert the CALMET winds into a
format suitable for input into the UAM model. If CALMET is to be run in this mode, an option is
provided to allow preprocessed surface and upper air observations to be input. The preprocessed input
file, DIAG.DAT, is compatible with the stand-alone version of the diagnostic wind field model developed
by Douglas and Kessler (1988).
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