Appendix b. equations – Campbell Scientific IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer User Manual
Page 59
Appendix B. Equations
TABLE B-1 lists variables and constants used in the following equations.
TABLE B-1. Table of Equation Variables and Constants
Variable or Constant
Description
Units
c
ρ
CO
2
Mass Density
mg·m
-3
v
ρ
H
2
O Mass Density
g·m
-3
d
ρ
Mass Density of Dry Air
g·m
-3
c
X
CO
2
Molar Mixing Ratio
(concentration relative to dry air)
µmol·mol
-1
v
X
H
2
O Molar Mixing Ratio
(concentration relative to dry air)
mmol·mol
-1
c
M
Molecular Weight of CO
2
44 mg·mmol
-1
d
M
Molecular weight of dry air
0.029 g·mmol
-1
v
M
Molecular weight of H
2
O
0.018 g·mmol
-1
P
Ambient Pressure
kPa
R
Universal Gas Constant
8.3143×10
–6
kPa·m
3
·K
-1
·mmol
-1
T
Ambient Temperature
o
C
e
Vapor Pressure
kPa
f
Enhancement Factor
Arbitrary
d
T
Dew Point Temperature
o
C
tmp
d
T
_
Temporary variable for dew point
calculation
Arbitrary
Mass Density from Molar Mixing Ratios
(
)
−
+
=
v
v
c
c
c
M
T
R
P
M
X
ρ
ρ
15
.
273
10
6
(B-1
1
)
(
)(
)
v
v
v
v
X
T
R
PM
X
+
+
=
1000
15
.
273
ρ
(B-2
1
)
(
)
(
)
15
.
273
+
−
=
T
R
M
e
P
d
d
ρ
(B-3)
(
)
15
.
273
1000
+
+
−
=
T
R
M
X
P
X
P
d
v
v
d
ρ
(B-4)
B-1