"John Hall" wrote in message
news
In article ,
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.
--
John Hall
"It is a very sad thing that nowadays there is so little useless
information."
Oscar Wilde (1854-1900)

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

Harold
--
Harold Brooks
Head, Mesoscale Applications Group
NOAA/National Severe Storms Laboratory

this shows the huge range -- 2:1 to 50:1 in1650 events - all over 6hr
accumulation periods.
Obviously there are many variables - as have been mentioned, apart from the
fact that the longer the snow lies the greater it is compacted.
His median figure of 14:1 seems about the best on offer as an extremely
approximate ratio.
With snow lying the 'water equivalent' is very important in assessing risks
of flooding when it melts. In years past this value was routinely measured
as part of the observational routine...I don't know whether it still is?
Cheers
John

In article ,
John Whitby writes:

"John Hall" wrote in message
news
In article ,
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.
--
John Hall
"It is a very sad thing that nowadays there is so little useless
information."
Oscar Wilde (1854-1900)

"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

"Philip Eden" philipATweatherHYPHENukDOTcom wrote in message
...
| --
| 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
|
When I was at school in 1963, we did a few rather dubious experiments,
collecting undisturbed snow from the middle of the sports field in different
sized containers (test tubes, mugs, oil cans, etc). Came up with a fairly
consistent figure of 11" of snow to 1" of water.
Ha, ha. Those were the good days, that is, when it snowed, it meant
something!!! Ten foot drifts kept the A34 north of Winchester closed for
over a week. By the time they started on it, the army took over a week to
clear 4 miles of it. It was completely beyond the capability of the council.

jim
Now in Northampton

Results....

Sligthly different filling method: Take a sheet of card and scoop up snow
and place it on top of other snow until the depth is about the same as the
deph of your glass/container, then cookie-cut the snow (i.e. push your
container into the snow), slide the card under the container and invert.
This was you should have a reasonably uncompress sample. Of course if your
snow is deep enough, just push the container into the snow only as far as
it's length.

Anyway, two samples: 16.9:1 and 15.4:1 . I'll send my MSc students out this
morning!

The raito will vary greatly - whether the snow has been wind-blown or
settled gently. Back in 1985 (17 March) we has a snowstorm in Grantham where
we had 15" in 2 hours (yeap). By the end of the next day this had compacted
(not melted) to ~8 inches...

Chris



"Brendan DJ Murphy" wrote in message
news
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?

In order to get the answer I performed the following experiment...

I took a pint beer-glass (one with an official pint crown and is 1 pint to
the rim, not a lined glass)

I filled it as best as I could with snow, taking care not to get air-gaps
and also care not to compress the snow. The snow must be kept "fluffy" and
not compacted in.

I skimmed the top of the glass so that I have a pint of fluffy snow. I
brought the glass indoors and watched my pint of snow melt.

I was surprised how little water there was left in the glass!
I measured the water (in ml) and divided that number in to 568ml (one
pint)

Before posting my result, I'd be interested to see if somebody else could
perform the same experiment and we will then compare our answers.

Its just a bit of fun,

regards

Brendan

On Feb 2, 7:06*pm, Harold Brooks wrote:
In article 8d88d8bd-bbf3-4587-9c25-9593ccc66882
@q30g2000prq.googlegroups.com, says...
[deletions]



Any tornadoes around 2 pm gmt today 'Arry?

Not in the US

'Srigh' I got a volcano instead. Quit 'appy with that.

Ta.

On Feb 3, 11:45*am, Weatherlawyer wrote:
On Feb 2, 7:06*pm, Harold Brooks wrote:

In article 8d88d8bd-bbf3-4587-9c25-9593ccc66882
@q30g2000prq.googlegroups.com, says...
[deletions]

Any tornadoes around 2 pm gmt today 'Arry?

Not in the US

'Srigh' I got a volcano instead. Quit 'appy with that.

Not quite:
"Beginning at 1:51 a.m. local time, the volcano belched out a mile-
high (1.6-kilometer-high) plume and continued smoking all day. Chunks
of rock from the eruption were found about 3,300 feet (1,000 meters)
from the volcano."
http://news.nationalgeographic.com/n...ctures-ap.html

Japan is about 9 hours ahead of us, more like 37 degrees from the
Dateline IIRC.

But interesting timing, none the less.
Beggars can't be choosers. Musn't grumble, know what I mean?

"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