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'[OT] How to measure snowfall?'
2000\02\17@174713 by Randy Glenn

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The rainfall thread reminded me of a question I was trying to answer: HYow would one
electronically measure snowfall, in centimetres? I was thinking maybe something to do with
sonar, or maybe an optical pair (transmitter and receiver on opposite sides) that travels
vertically?

-Randy Glenn
E-Mail: spam_OUTPICxpertTakeThisOuTspamyahoo.com
Web: http://i.am/PICxpert

Currently wondering why I can't get in to Safe Mode - where's a Mac when you need it?


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2000\02\17@181446 by Des Bromilow

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How about using Mass measuring techniques?
The reset function would be accomplished by a heating element and some holes inthe bottom of the receptacle, OR maybe you could collect the snow, and melt it in one operation, and then use the resulting water, (and a standard rain measuring sensor) to determine the snowfall. (this , coupled with a therometer, could allow the same instrument to measure two things ie: if it's below zero celcius, the "rainfall" is snow,if it's above zero degrees, then the 'rainfall" is rainfall., how's that for a versatile instrument!!!!!

Des


>>> Randy Glenn <.....picxpertKILLspamspam@spam@YAHOO.COM> 2/18/00 8:42:11 am >>>
The rainfall thread reminded me of a question I was trying to answer: HYow would one
electronically measure snowfall, in centimetres? I was thinking maybe something to do with
sonar, or maybe an optical pair (transmitter and receiver on opposite sides) that travels
vertically?

-Randy Glenn
E-Mail: PICxpertspamKILLspamyahoo.com
Web: http://i.am/PICxpert

Currently wondering why I can't get in to Safe Mode - where's a Mac when you need it?


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2000\02\17@182117 by Terry

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At 09:13 AM 2/18/00 +1000, you wrote:
>How about using Mass measuring techniques?
>The reset function would be accomplished by a heating element and some
holes inthe bottom of the receptacle, OR maybe you could collect the snow,
and melt it in one operation, and then use the resulting water, (and a
standard rain measuring sensor) to determine the snowfall. (this , coupled
with a therometer, could allow the same instrument to measure two things
ie: if it's below zero celcius, the "rainfall" is snow,if it's above zero
degrees, then the 'rainfall" is rainfall., how's that for a versatile
instrument!!!!!
>
>Des

The heat melted snow is below zero celcius? <BG>

2000\02\17@191321 by Wagner Lipnharski

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Snow volume is 100% relative to water volume?  I guess it is not 100%
the same always. So the same water volume can mean different volume of
snow.

Des Bromilow wrote:
{Quote hidden}

2000\02\17@192150 by TIM

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i heard the weather man say that 10 inches of snowfall equals 1 inch of rain
fall the other day on the television.. ok but i'm sure it has something to
do with the moisture content of the snow,,,
{Original Message removed}

2000\02\18@022556 by Ken Webster

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Wagner Lipnharski wrote:
>Snow volume is 100% relative to water volume?  I guess it is
>not 100% the same always. So the same water volume can mean
>different volume of snow.

Yeah and it would be interesting to measure the ratio.  A measure of how
dense the snow is.  I like it.



{Quote hidden}

Hmm... I wonder how much of the water would evaporate if you just heated the
funnel in a rain guage to barely above freezing.  I guess that would depend
on how cold it was plus the relative humidity plus how fast the snow was
falling.  I like the idea of letting the snow accumulate first .. then any
loss is limited to a shorter time window.


>> >>> Randy Glenn <EraseMEpicxpertspam_OUTspamTakeThisOuTYAHOO.COM> 2/18/00 8:42:11 am >>>
>> The rainfall thread reminded me of a question I was trying
>> to answer: HYow would one electronically measure snowfall,
>> in centimetres? I was thinking maybe something to do with
>> sonar, or maybe an optical pair (transmitter and receiver
>> on opposite sides) that travels vertically?

Or, since optical sensors are reasonably cheap, how about a pole with a lot
of optical sensors mounted every centimeter.  When the snow is up over a
sensor it will reflect the light back.  If a sensor is above the snow the
light will travel outward and not reflect back.


One other idea I was toying with is a real-time "is it snowing now?" sensor.
One thought I had was to aim a laser at a sensor a good distance away (a
hundred feet or so may be nice .. perhaps accomplished by folding the beam
back a few times with mirrors) and count how frequently the beam is
interrupted to measure snowfall "intensity".  Since the sizes of flakes
would vary it wouldn't really give you an accurate measurement (centemeters
per hour, etc.) but it would at least give a fair estimate.

Not that it is all that difficult to just look out the window, but, it would
be kind of cool to have a real-time "snow intensity" meter up on my web page
just for giggles.

Cheers,

Ken

2000\02\18@100646 by Wagner Lipnharski

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Not sure. The pole could be frozen and snow will stick to it, fooling
the sensor... even dirt can do it.
Heating the pole to keep it clean?  Too much energy wasted.
Weighting the snow? Not good, weight means water volume, not snow.

For now, I think a good solution would be sonar style. There are cheap
solutions to measure liquid and beans height in tanks and reservoirs.

Question:  How much snow absorbs RF transmitting signal?  I mean, if a
transmitter antenna is half buried into snow, how much of its
transmitted signal will be reduced?  Snow conduct electricity as water,
right? or wrong? You got the idea, hum?   Two antennas, two meters tall,
5 meters apart, mounted vertical from ground.  One transmitting another
receiving. The receiver is calibrated to indicate snow height based on
RF loss level.  I think 1mW of special chosen frequency transmitting
signal would be more than enough.

Wagner.

Ken Webster wrote:

> Or, since optical sensors are reasonably cheap, how about a pole with a lot
> of optical sensors mounted every centimeter.  When the snow is up over a
> sensor it will reflect the light back.  If a sensor is above the snow the
> light will travel outward and not reflect back.

2000\02\18@120746 by Alice Campbell

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this is actually really tricky.  The water content of snow is currently
measured in the Sierra Nevada, by the Calif. Div. of Water
Resources, by hand.  Strong young men go out on snow-courses
with a surveyor's rod to measure average thickness of snow, then
they manually cut a block of it, i think one square meter or 1
square foot, and melt it and measure the equivalent water depth in
inches.  So far, they havent found a better way, and you can bet
they wouldnt go to all this trouble if it was easy.  Since our water
supply depends on the Sierra snowpack, they dont mess around.

One of the many problems is that the density of snow is not
constant, but depends a lot on  how cold it was before, during, and
after the event.  Avalanches occur in the mountains when a layer of
new, wet snow is deposited on older snow that had enough time to
'cure' to a hard surface, so the two layers are not mechanically
interlocked.  Hence, the top layer slips off and slides down the hill.

The closest thing i have seen to workable is some form of time-
domain reflectrometry that uses the eches off the layers to
compute density and thickness.  Highway departments in
avalanche-prone areas are Very interested in instrumentation that
will help detect these conditions.

a.

{Quote hidden}

2000\02\18@135052 by Dan Michaels

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At 10:00 AM 02/18/2000 -0500, you wrote:
>Not sure. The pole could be frozen and snow will stick to it, fooling
>the sensor... even dirt can do it.
>Heating the pole to keep it clean?  Too much energy wasted.
>Weighting the snow? Not good, weight means water volume, not snow.
>
>Wagner.
>
>Ken Webster wrote:
>
>> Or, since optical sensors are reasonably cheap, how about a pole with a lot
>> of optical sensors mounted every centimeter.  When the snow is up over a
>> sensor it will reflect the light back.  If a sensor is above the snow the
>> light will travel outward and not reflect back.
>

Ken, Wagner,

They teach in Colorado avalanche schools that when you are caught
inside an avalanche it is pitch black - (even before you suffocate).

A series of light sensors on a pole would sense graded levels of
ambient light, depending upon their depth under the snow. No need
for light source or reflectors (at least in daytime). Sensors above
the surface, even covered with a layer of snow, would still sense
some light, depending upon the thickness of the layer, and after a
day or so, the snow would melt off them anyway (at least in Colorado
with its unusually large share of sunshine).

If you did a profile of light_sensed vs depth, you could probably
determine where the snow surface was fairly easily, and which
sensors above the surface might have snow stuck to them.

profile looks like:  ___________..---_--_---------  (_=black)

(some dirty sensors above the surface are shown).

In between snowstorms, you could determine which sensors might
be dirty by their diminished output. Once a week you could climb
the mountain (or whatever), to wash the sensors if necessary, and
get some exercise to boot. Try it now, while it's still winter.

- Dan Michaels
Oricom Technologies
http://www.sni.net/~oricom

2000\02\18@161258 by Mike Werner

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On Fri, Feb 18, 2000 at 10:00:50AM -0500, Wagner Lipnharski wrote:
> Not sure. The pole could be frozen and snow will stick to it, fooling
> the sensor... even dirt can do it.
> Heating the pole to keep it clean?  Too much energy wasted.
> Weighting the snow? Not good, weight means water volume, not snow.
>
> For now, I think a good solution would be sonar style. There are cheap
> solutions to measure liquid and beans height in tanks and reservoirs.
>
> Question:  How much snow absorbs RF transmitting signal?  I mean, if a
> transmitter antenna is half buried into snow, how much of its
> transmitted signal will be reduced?  Snow conduct electricity as water,
> right? or wrong? You got the idea, hum?

*Pure* water is an effective insulator.  Snow will not be absolutely
pure, simply due to atmospheric contaminants.  But I have to wonder
if there would be enough contaminant to provide conductance.

> Two antennas, two meters tall,
> 5 meters apart, mounted vertical from ground.  One transmitting another
> receiving. The receiver is calibrated to indicate snow height based on
> RF loss level.  I think 1mW of special chosen frequency transmitting
> signal would be more than enough.

Probably too much power at that close of a range.  At 5 meters you'd
be better off looking towards the microwatt level of power.  1mW at
VHF frequencies is enough to go multiple kilometers if line of sight.
To get any appreciable RF attenuation at only 5 meters you would
probably need to go with 1 microwatt or perhaps even less.
--
Mike Werner  KA8YSD           |  "Where do you want to go today?"
ICQ# 12934898                 |  "As far from Redmond as possible!"
'91 GS500E                    |
Morgantown WV                 |  Only dead fish go with the flow.

2000\02\18@190849 by Tom Handley

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  Wagner, Alice pretty much had the `real poop' on how to measure snow
pack. They do that on our local mountains. Back to general snowfall
measurements, most all commercial rain collectors have a heating element
built-in or as an option as mine does. This gives you the moisture content
of snowfall. However, the `1 to 10' rule to convert to snow depth is very
crude even if you had a consistent snowfall over a large area, no wind, and
Fred Astair and Gene Kelly out dancing and singing ;-)

  What NOAA, NWS and WMO recommend is taking measurements from different
sites that are representative of the region. In 1996 the NWS started phasing
out reports from airports due to urban congestion and the various micro
climates that surround such areas. They started a program where they use
Cooperative Observers (COOP) in the surrounding area. The observers are
trained and the methods are standardized. Basically, you use a `Snow Board'
which is a flat piece of wood, plastic, or metal, and a ruler to measure the
depth. You typically have several in the immediate area and you average the
readings.

  In any case, you want to both measure the average depth and the moisture
content. Here, you melt a known volume of snow, or use a heated collector.
You can also use a `10 to 1' rule to find the moisture content but it's not
as accurate. The key is taking readings from several locations in the
immediate area and combine that data with measurements from other sites in
the region. This gives a representative measure of average snowfall.

  For just about anything you want to know about measuring snowfall see:

     The Snow Booklet. A guide to the science, climatology, and measurement
     of snow in the United States
     http://ulysses.atmos.colostate.edu/~odie/snowtxt.html

  For links that have links to just about anything you want to know about
meteorology, standards, vendors, and projects, see my `pathetic' web page:

     http://www.teleport.com/~thandley/Wilbure.htm

  - Tom

At 10:00 AM 2/18/00 -0500, Wagner Lipnharski wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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