Hi,
We know that the standard density of air is 1.225 kg/m3 (at sea level, 15 oC, & 1 atm). The density, however, is not constant as it changes daily according to the local atmospheric pressure, temperature, elevation, and humidity maybe.
For a certain day(i), is it safe to apply the ideal gas law, i.e., ρi=PiM/RTi ? Is the elevation and humidity taken into account in this formula? Is there a better widely applicable recipes?
Your shared thoughts and discussions are highly appreciated,
Abdo,
The ideal gas law is a general rule, always applicable. Air can be modeled as ideal gas, but remember that it is a mixture of different components. And if you have condensation, the ideal gas law no longer applies.
Dear Abduslan,
Here some fortran code lines for the humid air density. Enter temperature t (°C), air pressure p (hPa) and specific humidity q (Kg/Kg) and you get your density in kg/m3
zt = dble(t)
zp = dble(p)
zh = dble(q)
zra = 287.04D0 ! Bolton, [MWR, 1980] en J/Kg/°K
zrvap = 461.51D0 ! constant for water vapor (J/kg/°K)
zrtt1 = 273.16D0 ! water triple point
zq0 = zrvap/zra-1.D0
zd = zp*100.D0/(zra*(zt+zrtt1)*(1.0D0+zq0*zh))
dens = zd
Regards, G.C.
Thanks to both of you Mr. Riess and Mr. Caniaux . Good to have different formulas to compare with.
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