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
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