Longwave Radiation and Snow Melting in NOAH LSM

Topics related to current and future physics in the WRF as well as any problems you may have.

Longwave Radiation and Snow Melting in NOAH LSM

Postby lbirch » Tue Apr 28, 2015 12:32 pm

Hi all,
When calculating the surface fluxes for melting snow, the NOAH LSM does not appear to account for the reflection of longwave radiation. In module_sf_noahlsm.F we see, that melting is calculated mostly from FDOWN, where
FDOWN = SOLDN * (1.0- ALBEDO) + LWDN

The snow emissivity of the surface in WRF is .95, so the fluxes reflected are not insignificant. Has anyone else noticed this problem in NOAH LSM?

To fix the problem of excess longwave radiation, I was considering changing FDOWN to

FDOWN = SOLDN * (1.0- ALBEDO) + EMISSI*LWDN

Do you think this will lead to any problems? As far as I can see, FDOWN is only used to compute net fluxes, so I think it makes sense to account for reflection in that part of the code.

Thanks,
L
lbirch
 
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