Campbell CR800 Series, Operator'S Manual

Page: 202 / 598

Section 7. Installation
202
7.7.9.1 OutputOpt Parameters
In the CR800 WindVector() instruction, the OutputOpt parameter defines the
processed data that are stored. All output options result in an array of values, the
elements of which have _WVc(n) as a suffix, where n is the element number. The
array uses the name of the Speed/East variable as its base. See table
WindVector() OutputOpt Options
(p. 202).
WindVector() OutputOpt Options
Option Description (WVc() is the Output Array)
0
WVc(1): Mean horizontal wind speed (S)
WVc(2): Unit vector mean wind direction (Θ1)
WVc(3): 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.
1
WVc(1): Mean horizontal wind speed (S)
WVc(2): Unit vector mean wind direction (Θ1)
2
WVc(1): Mean horizontal wind speed (S)
WVc(2): Resultant mean horizontal wind speed (U)
WVc(3): Resultant mean wind direction (Θu)
WVc(4): 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.
3 WVc(1): Unit vector mean wind direction (Θ1)
4
WVc(1): Unit vector mean wind direction (Θ1)
WVc(2): 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.
7.7.9.2 Wind Vector Processing
WindVector() uses a zero-wind-speed measurement when processing scalar wind
speed only. Because vectors require magnitude and direction, measurements at
zero wind speed are not used in vector speed or direction calculations. This
means, for example, that manually-computed hourly vector directions from 15
minute vector directions will not agree with CR800-computed hourly vector
directions. Correct manual calculation of hourly vector direction from 15 minute
vector directions requires proper weighting of the 15 minute vector directions by
the number of valid (non-zero wind speed) wind direction samples.