Only one of these keywords may be specified in a given run. If more than one is encountered, a non‑fatal warning message is generated and the first specification is used in the modeling. Also, since the regulatory default option includes a half life of 4 hours for exponential decay of SO2 in urban settings, any HALFLIFE or DCAYCOEF input conflicting with that option will be overridden if the DFAULT option is selected on the CO MODELOPT card.
3.2.6 Options for Elevated Terrain
Two optional keywords are available on the Control pathway to control the receptor options for modeling elevated terrain ‑ the TERRHGTS and ELEVUNIT keywords.
The TERRHGTS keyword controls whether the model assumes flat or elevated terrain. For elevated terrain, the terrain height should be specified for each receptor. The syntax and type of the TERRHGTS keyword are summarized below:
CO TERRHGTS FLAT or ELEV
where the FLAT secondary keyword forces flat terrain calculations to be used throughout, regardless of any terrain heights that may be entered on the Receptor pathway. Any terrain heights that are entered on the Receptor pathway are ignored if FLAT terrain is specified, and a non‑fatal warning message is generated. The ELEV secondary keyword indicates that terrain heights are allowed/expected on the Receptor pathway. The default terrian height of 0.0 meters is used if no value is given. For terrain above the release height (i.e., complex terrain), the models automatically truncate ("chop") the terrain to the physical release height(s) when modeling impacts at those receptors using the simple terrain (ISC) algorithm. Terrain above the release height is not truncated when the COMPLEX1 algorithm is used in ISCST. The models assume flat terrain as the default if no TERRHGTS keyword is present in the input runstream.
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castellano: DIS CUS DES RAD english: DIS CUS DES RAD
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