NoahMP - potential error in the computation of dry air density RHOAIR

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J

joelarnault

New member
Dear WRF user support,

I would like to draw your attention on a potential error in the calculation of the dry air density in NoahMP.
In phys/module_sf_noahmplsm.F, SUBROUTINE ATM, we have:

EAIR = QAIR*SFCPRS / (0.622+0.378*QAIR)
RHOAIR = (SFCPRS-0.378*EAIR) / (RAIR*SFCTMP)

I agree with the formula of EAIR (partial pressure of water vapor) if we assume that QAIR is the specific humidity.
However, I think the formula of RHOAIR (dry air density) should be:
RHOAIR = (SFCPRS-EAIR) / (RAIR*SFCTMP)
which comes from the following ideal gaz law equation:
SFCPRS = RHOAIR * RAIR * SFCTMP + EAIR

Would you confirm that?

many thanks in advance for considering this "small" issue
Joël
 
This topic has been moved to the Bug Report section of the forum. Someone will respond to your suggestion soon.
 
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