Specifications

Appendix B. Measurement Names and Meanings
B-5
Scalar mean horizontal wind speed, S:
S=(6s
i
)/N
where in the case of orthogonal sensors:
S
i
=(Ue
i
2
+Un
i
2
)
1/2
Unit vector mean wind direction, 41:
41=Arctan (Ux/Uy)
where
Ux=(6sin 4
i
)/N
Uy=(6cos 4
i
)/N
or, in the case of orthogonal sensors
Ux=(6(Ue
i
/U
i
))/N
Uy=(6(Un
i
/U
i
))/N
where U
i
=(Ue
i
2
+Un
i
2
)
1/2
Standard deviation of wind direction, V
V
(
4
1), using Yamartino algorithm:
V(41)=arc sin(H)[1+0.1547 H
3
]
where,
H=[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
FIGURE B-2. Mean Wind Vector
where for polar sensors:
Ue=(6S
i
Sin 4
i
)/N
Un=(6S
i
Cos 4
i
)/N
or, in the case of orthogonal sensors:
Ue=(6Ue
i
)/N
Un=(6Un
i
)/N