Prh p, Pp p ppm – Vaisala HMP155 User Manual
Page 83
Appendix A ______________________________________________________ Calculation Formulas
VAISALA _______________________________________________________________________ 81
where:
b0 = 0.13914993 * 101
b1 = -0.48640239 * 10-1
b2 = 0.41764768 * 10-4
b3 = -0.14452093 * 10-7
b4 = 0.65459673 * 101
a
i
=
Coefficients over ice
a-1 = -0.56745359*
104
a0 = 0.63925247*
101
a1 = -0.96778430*
10-2
a2 = 0.62215701*
10-6
a3 = 0.20747825*
10-8
a4 = -0.94840240*
10-12
a6 = 0.41635019*
101
The water vapor pressure is calculated using:
100
ws
w
P
RH
P
(9)
Parts per million by volume is calculated using:
w
w
v
P
p
P
ppm
6
10
(10)
Symbols:
T
d
=
dew point temperature (°C)
P
w
=
water vapor pressure (hPa)
P
ws
=
water vapor saturation pressure (hPa)
RH = relative
humidity
(%)
x
=
mixing ratio (g/kg)
p
=
atmospheric pressure (hPa)
A
=
absolute humidity (g/m3)
T
= temperature
(K)
h
= enthalpy
(kJ/kg)
= virtual
temperature