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SECTION 11. OUTPUT PROCESSING INSTRUCTIONS

11-2

There are three Output Options, which specify

the values calculated.

Option 0:

Mean horizontal wind speed, S.

Unit vector mean wind direction, Θ

ΘΘ

Θ1.

Standard deviation of wind direction, σ

σσ

σ(Θ

ΘΘ

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, Θ

ΘΘ

Θ1.

Option 2:

Mean horizontal wind speed, S.

Resultant mean wind speed, U.

Resultant mean wind direction, Θ

ΘΘ

Θu.

Standard deviation of wind direction, σ

σσ

σ(Θ

ΘΘ

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:

S

i

= horizontal wind speed

Θ

i

= horizontal wind direction

Ue

i

= east-west component of wind

Un

i

= north-south component of wind

N = number of samples

Calculations:

Scalar mean horizontal wind speed, S:

S=(ΣS

i

)/N

where in the case of orthogonal sensors:

S

i

=(Ue

i

2

+Un

i

2

)

1/2

Unit vector mean wind direction, Θ

ΘΘ

Θ1:

Θ1=Arctan (Ux/Uy)

where

Ux=(Σsin Θ

i

)/N

Uy=(Σcos Θ

i

)/N

or, in the case of orthogonal sensors

Ux=(Σ(Ue

i

/U

i

))/N

Uy=(Σ(Un

i

/U

i

))/N

where U

i

=(Ue

i

2

+Un

i

2

)

1/2

Standard deviation of wind direction, σ

σσ

σ(Θ

ΘΘ

Θ1),

using Yamartino algorithm:

σ

σσ

σ(Θ

ΘΘ

Θ1)=arc sin(ε)[1+0.1547 ε

3

]

where,

ε=[1-((Ux)

2

+(Uy)

2

)]

1/2

and Ux and Uy are as defined above.

Resultant mean horizontal wind speed, U:

U=(Ue

2

+Un

2

)

1/2

where for polar sensors:

Ue=(ΣS

i

Sin Θ

i

)/N

Un=(ΣS

i

Cos Θ

i

)/N

or, in the case of orthogonal sensors:

Ue=(ΣUe

i

)/N

Un=(ΣUn

i

)/N

Resultant mean wind direction, Θ

ΘΘ

Θu:

Θ

ΘΘ

Θu=Arctan (Ue/Un)

Standard deviation of wind direction, σ

σσ

σ(Θ

ΘΘ

Θu),

using Campbell Scientific algorithm:

σ

σσ

σ(Θ

ΘΘ

Θu)=81(1-U/S)

1/2

*** 70 SAMPLE ***

FUNCTION

This instruction stores the value from each

specified input location.

PAR. DATA

NO. TYPE DESCRIPTION

01: 2 Repetitions

02: 4 Starting input location no.

Outputs generated: 1 for each sample

1 2 ... 129 130 131 132 133 134 135 136 137 138 139 ... 220 221

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