Snow fall = percipitation?

[duke666]

Didn't know where else to put this, but as it's a Davis....

Thinking about putting a heater in my rain gauge for the winter which got me thinking. When the snow melts, it obviously gets counted as rain fall but is that how the MET office etc record it or do they prevent snow from falling into their rain gauges?

Duke

[Skywatch]

The console does seem to have a snow depth feature next to daily rainfall. I think this comes on when the rain gauge measures rain at or below freezing 32F (0C) the console automatically swiches to snow depth privided a heater is used.

[Bushman]

No.  The console does NOT convert snow-to-water equivalent.  Even if yu have  a heater it records precip.

[dalecoy]

As I understand it, if it falls from the sky it's precipitation - and if it doesn't, it isn't. 

Therefore, snow is precipitation, and dew and frost are not precipitation.  Of course, most rain gauges can't tell the difference.

[Skywatch]

No.  The console does NOT convert snow-to-water equivalent.  Even if yu have  a heater it records precip.

Bring that up with Davis or turn the backlight on and look in the area I mentioned. It's there. If I'm misunderstanding this forgive me, but I think we're talking about measuring snowfall depth equivilant to rain. I mentioned that the console appears to have a snowfall mode.

[Bushman]

No.  The console does NOT convert snow-to-water equivalent.  Even if yu have  a heater it records precip.

Bring that up with Davis or turn the backlight on and look in the area I mentioned. It's there. If I'm misunderstanding this forgive me, but I think we're talking about measuring snowfall depth equivilant to rain. I mentioned that the console appears to have a snowfall mode.

Yes, that icon appears but it is not connected to anything.  Snowfall mode was never implemented AFAIK.  Too bad...

[johnd]

Yes, that icon appears but it is not connected to anything.  Snowfall mode was never implemented AFAIK.  Too bad...

Agreed - that's been the situation ever since the VP1 was introduced IIRC.

(Presumably Davis did have some notion about introducing a snow depth sensor (?ultrasonic) at some stage, but it's never made an appearance. Any attempted conversion from snowfall melt to snow depth would be so rough as to be useless I would have thought, given that the equivalence ratio can vary between about 5:1 and 20:1 (snow:rain) depending on snow conditions.)

[moehoward4]

There is a 'snow' icon in the forecast area on the console, but I've never seen a snow measurement 'thing' in the rainfall totals.      Jack

[C5250]

Thinking about putting a heater in my rain gauge for the winter which got me thinking. When the snow melts, it obviously gets counted as rain fall but is that how the MET office etc record it or do they prevent snow from falling into their rain gauges?

Snowfall is measured two ways, snow depth and water equivalent. Water equivalent is how much rain fall there would have been if it had fallen as rain. Because the ratio between snow depth and water equivalent can vary greatly, it is important to have both measurements to improve future forecasts of snow depth.
 

[Skywatch]

No.  The console does NOT convert snow-to-water equivalent.  Even if yu have  a heater it records precip.

Bring that up with Davis or turn the backlight on and look in the area I mentioned. It's there. If I'm misunderstanding this forgive me, but I think we're talking about measuring snowfall depth equivilant to rain. I mentioned that the console appears to have a snowfall mode.

Yes, that icon appears but it is not connected to anything.  Snowfall mode was never implemented AFAIK.  Too bad...

Ok, Gives me something to bug Davis with LOL. I wounder why Davis did that? Oh well. I geuss it doesn't matter.

[duke666]

So the answer seems to be, if snow falls and melts and therefore triggers the rain gauge, it is an exceptable measurement of rain and does not need to be edited out of the records.

As I understand it, if it falls from the sky it's precipitation - and if it doesn't, it isn't. 
Therefore, snow is precipitation, and dew and frost are not precipitation.

Duke

[dalecoy]

So the answer seems to be, if snow falls and melts and therefore triggers the rain gauge, it is an exceptable measurement of rain and does not need to be edited out of the records.

It is a measure of precipitation, and should be handled as such.  Yes, the acceptable answer is to consider it to be rain.

[Bushman]

If you have a heater and know the temps at which the snow fell you can approximate the snowfall amount.  There is a NOAA chart for that somewhere on the Interweb...

[d_l]

If you have a heater and know the temps at which the snow fell you can approximate the snowfall amount.  There is a NOAA chart for that somewhere on the Interweb...

http://www.ncdc.noaa.gov/oa/climate/conversion/newsnowfall.html

[xykotik]

No.  The console does NOT convert snow-to-water equivalent.  Even if yu have  a heater it records precip.

Bring that up with Davis or turn the backlight on and look in the area I mentioned. It's there. If I'm misunderstanding this forgive me, but I think we're talking about measuring snowfall depth equivilant to rain. I mentioned that the console appears to have a snowfall mode.

Yes, that icon appears but it is not connected to anything.  Snowfall mode was never implemented AFAIK.  Too bad...

Ok, Gives me something to bug Davis with LOL. I wounder why Davis did that? Oh well. I geuss it doesn't matter.

That is a similar reason why Tivo and DirecTV had a falling out in the early 00's..  Philips built their Tivos with a USB port, but was ordered to disable it.  (Too many possibilities).  Then Hughes (owns Dtv) started making their own (sans USB) running the app they licensed from Tivo.  Then when Dtv decided to start charging extra for multi-room viewing, which also required deactivating the Tivo-brand units in favor of their own "new" singe-wire-multiX models (lease only), it didn't take long for the hackers to figure out how to enable the USB port on the Philips Tivos.

So, who can reverse engineer the Davis console to use that little icon? 

[duke666]

So, who can reverse engineer the Davis console to use that little icon?

I've started something now

I only wanted to know how to handle snow in the rain collector - many thanks dalecoy.

Duke

[dalecoy]

So, who can reverse engineer the Davis console to use that little icon? 

Why?  [What input device would be used?]

[dalecoy]

So, who can reverse engineer the Davis console to use that little icon?

I've started something now

I only wanted to know how to handle snow in the rain collector - many thanks dalecoy.

Duke

You're quite welcome.  Please note that there are several (rather small) errors associated with melting snow in the heated rain collector.  With a heater, very light snowfall will evaporate and not be measured.  Depending on the various temperatures, some heavier snowfall may sublimate.  And of course the time of measurement will generally lag the time of snowfall.  I'm not suggesting that any of those (or other) factors should really concern any of us - but measurement errors do exist, just as they do for measuring falling liquid.

[xykotik]

So, who can reverse engineer the Davis console to use that little icon? 

Why?  [What input device would be used?]

1.  Because it is fun to talk about possibilities.  That's why there are silly little icons available. 

2.  Anything is better than my daughter-with-ruler gauge, which hasn't provided a measurement since the first time I used it.

[dalecoy]

So, who can reverse engineer the Davis console to use that little icon? 

Why?  [What input device would be used?]

1.  Because it is fun to talk about possibilities.  ...

OK, just for fun - in the context of amateur weather as typically displayed on the Davis console:

1.  How would we define "snow"?  Is it an instantaneous measurement?  Or a total?  Over what period of time?  Is there a "rate" measurement, too?

2.  What sort of device(s) would be used to automatically report "snow" (as defined above)?   How often would the data be captured?

3.  Please remember, this must be just "snow" - not liquid, and not anything like "freezing rain".

4.  Oh, and we have to (some way) account for the fact that snow "compacts" as it collects.

5.  Finally, would this set of measurements have any correlation with the official NWS snow measurements?  (for example, http://www.nws.noaa.gov/os/coop/snowguid.htm).  I mention that only because of the frequent discussions in this forum about that sort of thing.

[xykotik]

What does COCORAHS and NOAA use to identify the amount of snow from it's different qualities?  Would that be the definative answer to the OP of "Snow fall = percipitation?"  Is it just a mark on the gauge that does not differentiate between cotton-candy fluff, shussable powder and wet snowball fodder?  Do you melt what your eye knows is snow and report the water equivalent?

In it's most basic form, it seems that an automated snow detector/gauge would have to report any (melted by heater) precip that it collected below a certain temp threshold as snow-precip. But a depth measurement by infrared, ultrasonic or other methods wouldn't differentiate between the different densities of sub-freezing precip or freezing-rain, and the different consistencies is what makes it important when deciding what do do with that snow-report (ie road condition or school closure forecasts) so that would indeed be a challenge.  Eyeballing it (not very quantifiable) is still probably the most reliable.

Perhaps these are just sub-sets of dalecoy's criteria if someone were to spec such a gauge.  It reminds me that most new tech is envisioned by marketing types, and then sent to the engineers to invent and tool it before the C-mas shopping season starts.

[smorris]

CoCoRaHS has extensive information on measuring snow HERE and their training slide show on how to measure snow HERE I just got to melt my first bit of sleet yesterday.

Steve

[C5250]

1.  How would we define "snow"?  Is it an instantaneous measurement?  Or a total?  Over what period of time?  Is there a "rate" measurement, too?

Why are you complicating it? There are three measurements, snow depth, snow fall and water equivalent. Each is  well defined by the NWS. Snow depth being the average depth of snow on the ground (generally reported at a specific time, but it is an instantaneous measurement). Snow fall is measured on a snow board (or other flat surface) at specific intervals. Water equivalent is obtained by melting snow fall.

I don't do water equivalent. But I do do snow fall and depth, it's not at all unusual for snow fall to be more than depth, because of compaction or melting.

[dalecoy]

1.  How would we define "snow"?  Is it an instantaneous measurement?  Or a total?  Over what period of time?  Is there a "rate" measurement, too?

Why are you complicating it? There are three measurements, snow depth, snow fall and water equivalent. Each is  well defined by the NWS. Snow depth being the average depth of snow on the ground (generally reported at a specific time, but it is an instantaneous measurement). Snow fall is measured on a snow board (or other flat surface) at specific intervals. Water equivalent is obtained by melting snow fall.

I don't do water equivalent. But I do do snow fall and depth, it's not at all unusual for snow fall to be more than depth, because of compaction or melting.

What snow measurement would you display on the Davis console, and how often would it be updated?

I didn't intend to complicate it.  In the context of "Snow" reported on a Davis Console (which is the theoretical subject being discussed, just for fun), what would you want to see reported?  Snow depth? [starting at zero in the fall, increasing and decreasing throughout the winter, going to zero in the spring] Or snow fall (at what specific interval?)

In other words, what would the "snow" icon on the Davis console screen actually report?  

Knowing the "meaning" is essential to even thinking about what sort of device would automatically measure and report it.

I have trouble envisioning a device that would automatically measure snow depth.  I can envision a snow fall device, but I'm not sure that the average weather enthusiast would want the reading to only change once (or 4 times) per day on the console.

[C5250]

First, the snow icon is something different, that appears when the console believes snow is likely.  I've seen it many times.

The text "snow depth" on the console suggests an automated snow depth measurement. I'm sure anyone who has tried that knows how difficult that is. I would imagine that would be updated, maybe every 15 minutes, or maybe once an hour, presumably from averaged readings.

I really can't see any easy way to automate a consumer level snow fall measurement. The rules for that require that the surface be cleared at least once a day, and no more often than every six hours.