Vaisala AWS330 - Manual (Page 289)

Appendix B ______________________________________________________ Calculation Formulas
VAISALA ______________________________________________________________________ 287
Wind Speed (U
2
)
Estimate wind speed at 2 m height when measured at height z.






−
=
) 42 . 5 ) 8 . 67 ln((
87 , 4
2 z
U U
z
where
Uz = Wind speed measured at height z [ms -1 ]
z = Height of wind speed measurement [m]
Vapor Pressure Deficit (e
a
-e
d
)






− 




 +
= − =
d
a a
d a
e
T e T e
e e VPD
2
) ( ) (
) ( min max
where
e
a
= Saturation vapor pressure [kPa]
e
d
= Actual vapor pressure [kPa]






+
=
3 . 237
27 . 17
exp 611 . 0 ) (
max
max
max T
T
T e
a






+
=
3 . 237
27 . 17
exp 611 . 0 ) (
min
min
min T
T
T e
a






+ 





=
100
) (
2
1
100
) (
2
1
min
max
max
min
RH
T e
RH
T e e
a a d
where
T
max
= Maximum daily temperature [ ° C]
T
min
= Minimum daily temperature [ ° C]
e
a
(T
max
) = Saturation vapor pressure at T
max
e
a
(T
min
) = Saturation vapor pressure at T
min
e
d
(T
max
) = Actual vapor pressure at T
max
e
d
(T
min
) = Actual vapor pressure at T
min
RH
max
= Maximum daily relative humidity [%]
RH
min
= Minimum daily relative humidity [%]