SECTION 11. OUTPUT PROCESSING INSTRUCTIONS

In an example where the scan rate is 1 second and the Output Flag is set every 60 minutes, the standard deviation is calculated from all 3600 scans when the sub-interval is 0. With a sub-interval of 900 scans (15 minutes) the standard deviation is the average of the four sub-interval standard deviations. The last subinterval is weighted if it does not contain the specified number of scans.

There are three Output Options that specify the values calculated.

Option 0:

Mean horizontal wind speed, S. Unit vector mean wind direction, Θ1. Standard deviation of wind direction, σ(Θ1).

Standard deviation is calculated using the Yamartino algorithm. This option complies with EPA guidelines for use with straight- line Gaussian dispersion models to model plume transport.

Option 1:

Mean horizontal wind speed, S. Unit vector mean wind direction, Θ1.

Option 2:

Mean horizontal wind speed, S. Resultant mean wind speed, U. Resultant mean wind direction, Θu. Standard deviation of wind direction, σ(Θu).

This standard deviation is calculated using Campbell Scientific's wind speed weighted algorithm.

Use of the Resultant mean horizontal wind direction is not recommended for straight- line Gaussian dispersion models, but may be used to model transport direction in a variable-trajectory model.

Measured raw data:

Scalar mean horizontal wind speed, S:

S=(ΣSi)/N

where in the case of orthogonal sensors: Si=(Uei2+Uni2)1/2

Unit vector mean wind direction, Θ1:

Θ1=Arctan (Ux/Uy)

Si = horizontal wind speed Θi = horizontal wind direction

Uei = east-west component of wind Uni = north-south component of wind N = number of samples

Calculations:

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