Questions on Runoff Components in CLM5 BGC-CROP Mode (ctsm5.1.dev118)

[liliyao]

Hi,

I am working with CLM5 BGC-CROP mode from ctsm5.1.dev118. I have questions regarding which runoff outputs should be included for surface runoff and subsurface runoff, respectively.

Q1: In the h0 file, the long name of "QOVER" is the "total surface runoff (includes QH2OSFC)." However, based on a previous thread, it seems that "QOVER" does not include "QH2OSFC" How to configure a transient climate simulation with constant surface data?

Q2: Does "QOVER" include "QRGWL" ((surface runoff at glaciers (liquid only), wetlands, lakes; also includes melted ice runoff from QSNWCPICE))?

In other words, is surface runoff equal to QOVER, or is it equal to QOVER + QH2OSFC + QRGWL?

Q3: Does "QDRAI" (sub-surface drainage) include "QDRAI_PERCH" (perched wt drainage)? Since my research focuses on subsurface runoff, should I sum QDRAI and QDRAI_PERCH to obtain "subsurface runoff"?

I apologize if these questions sound repetitive, but I really want to confirm the definitions of these runoff components.

Thank you very much!

 

[oleson]

(1) QOVER does include QH2OSFC. See this in SoilHydrologyMod.F90:

! ------------------------------------------------------------------------
! Set qflx_surf for hydrologically-active columns
! ------------------------------------------------------------------------

do fc = 1, num_hydrologyc
c = filter_hydrologyc(fc)
! Depending on whether h2osfcflag is 0 or 1, one of qflx_infl_excess or
! qflx_h2osfc_surf will always be 0. But it's safe to just add them both.
qflx_surf(c) = qflx_sat_excess_surf(c) + qflx_infl_excess_surf(c) + qflx_h2osfc_surf(c)
end do

The post you referenced was referring to QH2OSFC in the urban model, where it is not an active component. It should be zero for urban areas.

(2) No

(3) No. The description for QDRAI_PERCH (qflx_drain_perched in the code) is "sub-surface runoff from perched wt", so you could sum them.

 

[liliyao]

Thank you so much, Dr. Oleson!