Specifications

Section 6. Data Table Declarations and Output Processing Instructions
Parameter
& Data Type
Enter
OutputOpt Value Outputs (for each rep)
Constant 0 1. Mean horizontal wind speed, S.
2. Unit vector mean wind direction, Θ1.
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
1. Mean horizontal wind speed, S.
2. Unit vector mean wind direction, Θ1.
2 1. Mean horizontal wind speed, S.
2. Resultant mean wind speed,
U
.
3. Resultant mean wind direction, Θu.
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.
When a wind speed sample is 0, the instruction uses 0 to process scalar or
resultant vector wind speed and standard deviation, but the sample is not used
in the computation of wind direction. The user may not want a sample less
than the sensor threshold used in the standard deviation. If this is the case,
write the datalogger program to check wind speed, and if it is less than the
threshold set the wind speed variable equal to 0 prior to calling the data table.
Standard deviation can be processed one of two ways: 1) using every sample
taken during the output period (enter 0 for the Subinterval parameter), or 2)
by averaging standard deviations processed from shorter sub-intervals of the
output period. Averaging sub-interval standard deviations minimizes the
effects of meander under light wind conditions, and it provides more complete
information for periods of transition
1
.
Standard deviation of horizontal wind fluctuations from sub-intervals is
calculated as follows:
σ(Θ)=[((σΘ
1
)
2
+(σΘ
2
)
2
...+( σΘ
M
)
2
)/M]
1/2
where σ(Θ) is the standard deviation over the output interval, and σΘ
1
...
σΘ
M
are sub-interval standard deviations.
1
EPA On-site Meteorological Program Guidance for Regulatory Modeling
Applications.
6-31