Question on input geopotential height

[maR_Kus]

Dear All,

I am trying to force WRF with some CMIP6 models. Among the 3D mandatory input fields needed to run WRF there is the geopotential height.

Actually, considering a given CMIP6 model, I have interpolated T,U,V,Q from hybrid model levels to constant pressure levels without providing the geopopential height as input; WPS, real and WRF do not complain about the lack of the geopotential and I can complete the simulaton. I was wondering whether this is correct, as this variable is not always available for most of CMIP6 models? In case it would be wrong, why WRF is able to complete the simumation and produce reasonable outputs?

Thanks into advance for clarifications,
Markus

 

[Ming Chen]

Markus,
If 3D geopotential height data are not included in the during data, then REAL program will calculate this variable based on other input data. Please see the following piece of code in dyn_em/module_initialize_real.F:

! Some data sets do not provide a 3d geopotential height field.

IF ( grid%ght_gc(i_valid,grid%num_metgrid_levels/2,j_valid) .LT. 1 ) THEN
\
DO j = jts, MIN(jte,jde-1)

DO k = kts+1 , grid%num_metgrid_levels

DO i = its, MIN(ite,ide-1)

IF ( skip_middle_points_t ( ids , ide , jds , jde , i , j , em_width , hold_ups ) ) CYCLE

grid%ght_gc(i,k,j) = grid%ght_gc(i,k-1,j) - &

R_d / g * 0.5 * ( grid%t_gc(i,k ,j) * ( 1 + 0.608 * grid%qv_gc(i,k ,j) ) + &

grid%t_gc(i,k-1,j) * ( 1 + 0.608 * grid%qv_gc(i,k-1,j) ) ) * &

LOG ( grid%p_gc(i,k,j) / grid%p_gc(i,k-1,j) )

END DO

END DO

END DO

END IF


Hope this is helpful for you.

 

[maR_Kus]

Ming, thanks a lot for the quick reply and the helpful information.