Specifications

Section 6. Data Table Declarations and Output Processing Instructions
Unit vector mean wind direction, 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(Θ1), using Yamartino algorithm:
σ(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
U
Un
Ue
FIGURE 6.4-4. Mean Wind Vector
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, Θu:
Θu=Arctan (Ue/Un)
Standard deviation of wind direction, σ(Θu), using Campbell Scientific
algorithm:
σ(Θu)=81(1-
U
/S)
1/2
6-33