Vaisala AWS330 - Manual (Page 281)

Appendix B ______________________________________________________ Calculation Formulas
VAISALA ______________________________________________________________________ 279
QNH Pressure
QNH, the pressure reduced to mean sea level according to ICAO
standard atmosphere, is calculated as follows:
ALT
T
e QFE QNH ⋅ + ⋅ = 00325 . 0 2 . 288
1
where
T
1
= 0.03416 ⋅ ALT ⋅ [1 - 0.19025 ⋅ (ln (QFE) - 6.92087)]
ALT = Station altitude [m]
QFE = Station level air pressure [hPa]
QNH = Sea level pressure [hPa]
ln( )
= Natural logarithm function
Table 117 Inputs for QNH Pressure Calculation
Input Variable
Atmospheric pressure (QFE)
PAAVG1M; see Table 5 on page 23
Reduction level (ALT) Station parameter 'pslevel'