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3.5.10 Specifying Average Wind Speeds for the Long Term Model

 

     The ISC Long Term model uses joint frequencies of wind speed class by wind direction sector by stability category as the basic meteorological input to the model.  These STAR summaries (for STability ARray) are described in more detail in Section 3.5.1.2.  The optional AVESPEED keyword on the ME pathway allows the user to specify the median wind speed for each of the wind speed categories in the STAR summary.  The syntax and type of this keyword are summarized below:

 

Syntax:

ME AVESPEED  Ws1  Ws2  Ws3  Ws4  Ws5  Ws6

Type:

Optional, Non‑repeatable

 

where the Ws1 through Ws6 parameters are the median wind speeds (m/s) for each of the six wind speed categories.  The default values used by the model in the absence of the AVESPEED keyword are as follows:  1.50, 2.50, 4.30, 6.80, 9.50, and 12.50 m/s.

 

3.5.11 Specifying Average Temperatures for the Long Term Model

 

     For the ISC Long Term model, the user must specify average values of ambient temperature following the AVETEMPS keyword.  The following syntax is used:

 

Syntax:

ME AVETEMPS  Aveper  Ta1 Ta2 Ta3 Ta4 Ta5 Ta6

Type:

Mandatory, Repeatable

 

where the Aveper parameter specifies the long term averaging period for the following inputs, and must be one of the secondary keywords used on the Long Term AVERTIME card described in Section 3.2.3.2 (e.g., JAN, WINTER, ANNUAL, etc.).  The Ta1 through Ta6 parameters are the average ambient temperatures (K) for each of the six stability categories, A through F.  The AVETEMPS keyword is repeated for each of the averaging periods being processed.  Common practice is to apply the average daily maximum temperature for the time period being modeled to stability classes A, B and C, the average daily minimum temperature to stability classes E and F, and the average daily temperature to stability class D.  These average temperatures may be obtained from various climatological summaries, including the Local Climatological Data - Annual Summary published for major National Weather Service stations by the National Climatic Data Center in Asheville, North Carolina.

 

     The following example illustrates the use of the AVETEMPS keyword:

 

ME AVETEMPS  WINTER  3*280.0  275.0  2*270.0

ME AVETEMPS  SPRING  3*285.0  280.0  2*275.0

ME AVETEMPS  SUMMER  6*293.0

ME AVETEMPS   FALL   280. 280. 275. 270. 265. 265.

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where repeat values have been used for the unstable and stable classes for winter and spring, and for all classes for summer.

 

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