[Wrf-users] Noah fix in WRF 3.3

[Kevin Matthew Nuss]

Greetings,

I reported that bug and they correctly, imho, fixed it.

The runoff variable is meant to be a composite of two variables,  runoff2
and runoff3, which are two different kinds of underground runoff valaues.
But they added them together twice, once in module_sf_noahlsm.F and again in
module_sf_noahdrv.F, which caused runoff3 to get counted twice. Runoff2 is
the normal flow of water out the bottom of the soil. Runoff3 is the excess
water if the bottom soil layer is somehow more than saturated - the excess
is just taken out.

If you use such things, please be aware that the two accumulated values,
SFCRUNOFF and UDRUNOFF are not set to zero at the beginning of a run for
Noah. It is for RUC LSM. You may get a zero initial value by chance but
don't depend on that, I don't. I reported this to wrfhelp, but was not able
to get the idea across that accumulated values should start with zero. So
they didn't fix it. Here is what I did to set things to zero in V3.2.1:

In module_sf_noahdrv.F, about line 652, which is within the loops going thru
every cell during just the first timestep, I added these lines:

          ! Initialize surface and under ground runoff values
          SFCRUNOFF(I,J) = 0.0
          UDRUNOFF(I,J) = 0.0

Yes, I know that Fortran lets you set all values in an array without
looping, but I try to make my code fit in with that to which I am adding.

By the way, the variables are SFCRUNOFF and UDRUNOFF in the code, but
SFCROFF and UDROFF in the output files.

Hope that helps,
Kevin

On Thu, Apr 14, 2011 at 7:38 AM, Huber, David <dbh409 at ku.edu> wrote:

> Hello,
>
> I noticed in the fixes listed for WRF 3.3 that the Noah LSM underground
> runoff was fixed.  I was wondering if you know exactly what the problem was
> and how it was fixed.
>
> Thanks,
>
> Dave
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