Campbell Scientific EC155 CO2 and H2O Closed-Path Gas Analyzer and EC100 Electronics with Optional CSAT3A 3D Sonic Anemometer - Manual (Page 60)

Appendix B. Useful Equations
( ) 





+
−






+
=
v
v d
d X
X
T R
PM
1000
1
15 . 273
ρ
(B-5)
Dew Point from Molar Mixing Ratio
tmp d
tmp d
d T
T
T
_
_
502 . 17
97 . 240
−
=
(B-6)
( ) 





+ ⋅
=
v
v
tmp d X f
P X
ln T
1000 61121 . 0 _
(B-7)
( ) ( )
2 9 5 10 9 . 5 10 2 . 3 00072 . 1 PT P f − − Ч + Ч + = (B-8)
Water Vapor Molar Mixing Ratio from Dew Point
1000
e P
e
X
v −
= (B-9)






+
⋅ ⋅ =
d
d
T
T
EXP f e
97 . 240
502 . 17
61121 . 0
(B-10)
Water Vapor Mass Density from Dew Point
( )( )
( ) 





+ +
=
d
d
v T
T
EXP
T R
f
97 . 240
502 . 17
15 . 273
61121 . 0 018 . 0
ρ
(B-11)
Vapor Pressure from Molar Mixing Ratio and Water Vapor Density
v
v
X
P X
e
+
=
1000
(B-12)
( )
v
v
M
T R
e
15 . 273 +
=
ρ
(B-13)
Equations (1) and (2) were derived from Leuning, 2004; Eq. 6.23.
Equations (6) - (8) and (10) - (11) were derived from Buck, 1981; Eq. 2a, 3a,
and 6.
B-2