[NARCCAP-discuss] Snow Density

[Jonas Roberts]

Perfect, thanks Seth.

On Tue, Aug 7, 2012 at 5:38 PM, Seth McGinnis <mcginnis at ucar.edu> wrote:

> Hi Jonas,
>
> We've been looking into this, and it appears to be the case that the
> published
> snow variables, regardless of whether they are named snd or snw, are
> actually
> snow-water-equivalent.  The only exception is MM5I-ncep; I suspect that in
> that
> case we have snow depth instead, but the modeling team is still
> investigating.
>
> To resolve this confusion, we're going to convert everything to the same
> units,
> clean up the metadata, and republish it as a new variable named "swe".
>  This
> task is close to done, and I expect to publish swe files soon.  There will
> be
> an announcement on the narccap-announce mailing list when it happens.
>
> (I believe that the published snd files contain swe in units of meters,
> and the
> published snw contain swe in units of millimeters, but email me if you
> find any
> exceptions.)
>
> Cheers,
>
> --Seth
>
>
> On Tue, 7 Aug 2012 15:51:35 -0230
>  Jonas Roberts <jonaspmr at gmail.com> wrote:
> >Hey Seth,
> >
> >I wanted to follow up about snow density. I've noticed that some
> >models (e.g.WRFG_ccsm) state that snd is "snow depth in water
> >equivalent" in metres (from ncdump -h) while others (e.g. CRCM_ccsm)
> >just say "snow surface thickness" without units or further
> >elaboration.
> >
> >After plotting an area-averaged mean annual cycle of snd for my region
> >of interest (northeastern Canada) it looks like values across several
> >models are of similar magnitude (off by a factor of 2 at most)
> >irrespective of what ncdump -h says.
> >
> >Do you have any more insight into whether snd is actually snow water
> >equivalent for all models?
> >
> >Thanks again,
> >Jonas
> >
> >On Thu, Mar 22, 2012 at 8:13 PM, Seth McGinnis <mcginnis at ucar.edu> wrote:
> >> Hi Jonas,
> >>
> >> My (limited) understanding is that, unless the model has an unusually
> >> sophisticated snow algorithm, the density of snow in a climate model is
> >> typically 0.1.  So you can convert snd (snow depth) to swe
> >> (snow-water-equivalent) by simply dividing by 10.
> >>
> >> I plan to check with the modelers at our PIs meeting in a couple weeks
> to
> >find
> >> out whether that's true for all the NARCCAP models.  If I find any
> >exceptions,
> >> I'll post to the mailing list about it.
> >>
> >> As for the download problem, that sounds like a database error in ESG;
> I'll
> >> pass it on to the ESG team.  Thanks!
> >>
> >> Cheers,
> >>
> >> --Seth
> >>
> >>
> >> On Thu, 22 Mar 2012 09:56:55 -0230
> >>  Jonas Roberts <jonaspmr at gmail.com> wrote:
> >>>Hello,
> >>>
> >>>Is there a snow density value corresponding to the snow depth
> >>>variable? Is there an average value we should assume or some way of
> >>>determining the density from other variables? I'm trying to determine
> >>>the snow water equivalent in the snow pack.
> >>>
> >>>Also, when downloading snd data (individually) from the CRCM_ccsm data
> >>>set there were errors when downloading files like snd_CRCM_ccsm_
> >>>1991010103.v1.nc. However if I removed the .v1 from the URL then the
> >>>download started.
> >>>
> >>>Thanks in advance,
> >>>Jonas Roberts
> >>>PhD Candidate
> >>>Faculty of Engineering and Applied Science
> >>>Memorial University of Newfoundland
> >>>_______________________________________________
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> >>>narccap-discuss at mailman.ucar.edu
> >>>http://mailman.ucar.edu/mailman/listinfo/narccap-discuss
> >>
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