QRUNOFF versus the sum of QDRAI, QOVER, and QRGWL

[jsmankin@ldeo_columbia_edu]

Hi, In the technical note (NCAR/TN-478+STR, pg 193), it says that "the total liquid water runoff at the land model resolution (kg m-2s-1) is Rliq = qover +qdrai +qrgwl" .  This is what I understand as being routed to the RTM. I find no mention of  qrunoff in the technical note. However,  the history fields (http://www.cesm.ucar.edu/models/cesm1.2/clm/models/lnd/clm/doc/UsersGuide/history_fields_table_40.xhtml) note that QRUNOFF is the total liquid runoff (not including QSNWCPICE). I figured the total liquid runoff (the sum of QDRAI+QOVER+QRGWL) and the QRUNOFF fields would be the same (both in mm/s). They are not. Does anyone have insight into their difference and what they hydrologically represent in the model? thanks! justin

 

[oleson]

I assume you are working with CLM4.0, not CLM4.5, since you are pointing to the CLM4.0 technical note?The CLM4.0 code seems to indicate that QRUNOFF = QOVER + QDRAI + QRGWL, unless irrigation is on.  I checked an annual mean CLM4.0 file I have and it seems that the equation balances.If you are using CLM4.5, then the equation is slightly different:
QRUNOFF = QOVER + QDRAI + QRGWL + QH2OSFCwhere QH2OSFC is "surface water runoff" Hope this helps