Re: Some thoughts on recurrence intervals

Kent Crispin (kent@songbird.com)
Mon, 29 Sep 1997 17:53:44 -0700


On Mon, Sep 29, 1997 at 05:48:37PM +0000, Benjamin Harding wrote:
> On 29 Sep 97 at 14:00, Earl Perry wrote:
>
> > Warm rain on isothermic snow banks is a partial explanation
> > for the Christmas floods on the Eel in '64. This condition
> > has the potential to put a hydrograph right over all previous
> > scales;
>
> (Are you all bored with all this hydrology? Should we stop
> now?)

Not yet :-)

> Well this rain on snow thing is overrated. It's all about
> energy.
[interesting point deleted]
>
> I think the real impact of snow is twofold. First, water
> tends to run efficiently on its surface or channels within it
> and thus get to streams _quickly_ (increasing peak flows) and
> without too much infiltration. Second, the soil below
> isothermal snow should be saturated and unable to take up much
> additional water.

There may be other factors. Unconsolidated snow is an extremely good
insulator -- rain, by compacting the snow, may cause solar energy to
be significantly more efficient at melting it. Also, warm rain means
warm air, and, while the specific heat of air is very low, there's
lots of it -- the ratio of the volume of air to the volume of the
rain is probably many thousands of times.

-- 
Kent Crispin				"No reason to get excited",
kent@songbird.com			the thief he kindly spoke...
PGP fingerprint:   B1 8B 72 ED 55 21 5E 44  61 F4 58 0F 72 10 65 55
http://songbird.com/kent/pgp_key.html
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