"Philip Eden" philipATweatherHYPHENukDOTcom wrote in message
...
"John Hall" wrote:
John Whitby writes:
"John Hall" wrote:
Brendan DJ Murphy writes:

I've always wanted to know how much precipitation (in rain mm) is
required to produce 1 foot of snow.

I've heard statements such as "1 foot of snow is equivalent to 1
inch
of rain" (ie: 12:1 ratio)
Ive also heard "1mm of rain is equivalent to 1cm of snow" (ie:
10:1
ratio)
Which one is correct?
snip

The answer is both/neither. The "drier" the snow, the more air it
contains and so the lower the water content. Dry snow will have
the 10:1
or 12:1 ratio you quote. Really wet snow, close to turning to
sleet/rain
can have a ratio as low as 4:1.

Harold Brooks in earlier post said

"Several years ago, some colleagues and I looked at the snow/liquid
ratio
for 1650 snowfall events from a number of sites in the US. The
ratio
ranged from ~2:1 to ~50:1. Our mean was 15.6:1 and the median was
14:1
(we used 6-hour snow accumulation obs-the ratios would be smaller
for
longer time periods). The paper is online at "

http://www.nssl.noaa.gov/~brooks/pap...reetal2006.pdf

Yes, I saw that after writing my post. I was surprise that the mean
and
median values were so high. I would guess that US experience might
be
different from that in the UK, because much of their snow falls at
lower
temperatures than we are used to here and so tends to be drier.
--
Agreed. 10:1 is a reasonable average figure for the UK. I don't
think I had ever measured anything above 20:1 until we did a
similar experiment on this very newsgroup during the very fluffy
snowfall of 27th (I think) December 2000, when I measured
30:1. Last October's snowfall produced 7:1.

Philip


Well, Here are my results from yesterday's snow samples

My pint of snow resulted in 129ml of water.
This is a quite surprisng 4.4 : 1 ratio

My wife independently took a sample taken from an entirely different
area of the garden.
Her glass was almost identical. about 125ml.

Almost a quarter of the glass! I did not expect to see that much
water!

regards

Brendan