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
eQFEQNH
00325.02.288
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 115 Inputs for QNH Pressure Calculation
Input Variable
Atmospheric pressure (QFE) PAAVG1M; see Table 5 on page 23
Reduction level (ALT) Station parameter 'pslevel'
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