58
whereby
B
n
= measured air pressure
QNH = corrected air pressure from the measuring point to the sea level at standard atmosphere
H
B
= altitude difference measuring point to the sea level in m
T = 273.15 K + t (with t=air temperature in °C)
C
h
= Constant 0.12 K/hPa
e = steam at station height (hPa)
e = SVP(TT) ·RH
with
RH = relative air humidity in %
SVP(TT) = saturation vapour pressure in mbar over water at the air temperature TT in °C, SVP(TT)
formula see dew point
12.4.10. Annex – formula air pressure over sea level QFF
The QFF-calculation takes place under consideration of the real atmosphere at the measuring point.
QFF=B
n
·2,7182183^(H
B
·0,03416356/(T+e·C
h
+(H
B
·0,00325)))
whereby
B
n
= measured air pressure
QFF = corrected air pressure from the measuring point to the sea level at the atmosphere at the
measuring point
H
B
= altitude difference measuring point to the sea level in m
T = 273.15 K + t (with t=air temperature in °C)
C
h
= Constant 0.12 K/hPa
e = steam at station hight (hPa)
e = SVP(TT) ·RH
with
RH=relative air humidity in %
SVP(TT) = saturation vapour pressure in mbar over water at the air temperature TT in °C, SVP(TT)
formula see dew point
