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SnowByWeight

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PaulMy:
Winter season is upon us, so away with the inner tube and on to SWE measuring.

I've been sending to CoCoRaHS since February 2014 and have always used the melting of snow in the outer cylinder to get SWE.
More recent I have just let the snow melt in the outer tube and then submit the results.  This can sometimes take over half an hour.
In a recent emailing CoCoRaHS provided a link to the weighing method SnowbyWeight_v1.0.ppt (cocorahs.org) so decided to get a cheap scale and try it.  This is a scale to 0.5 gram precision and this should be fine as 1 gram = 0.126 mm and the metric precipitation is at 0.2 mm increment.

I've used the weight method the past 3 days and then also continued with the melting to make a comparison.  This seemed fine as both methods were within 0.2 mm.  If you are doing the snow measuring and SWE what is your preference?

Enjoy,
Paul

WheatonRon:
I have used weighing the exterior CoCo gauge for years and it works perfectly. First, weigh the gauge empty, excluding the inner tube and the top—make sure it is clean from debris. In my situation, it weighs 460 grams. When measuring precipitation in the gauge, snow or rain, weigh it. Then deduct the weight of the gauge itself and the result is then divided by 201 to get inches of water. For example, I get up in the morning and get the CoCo gauge, bring it inside, snow and all, then weigh it. If it weighs 500 grams, subtract the weight of the gauge itself (460 grams) results in 40 grams of water content in the CoCo gauge. Divide the 40 by 201 gives you .199 inches of water, rounded, .20. This works year round and is quite simple to calculate.

CW2274:
Somewhat similar, but whenever I calibrate a rain gauge, I always use volume to get me close, then weight as a fine tune. With a calibrated and precise enough scale, always more accurate than volume.

miraculon:
I have been using the weighing method for several years myself. I have the "approved" Escali scale.

Since I normally measure the precipitation (either by tube or weight) out in the garage, I have a lunch heater that the Escali fits nicely into out there. I bought a temperature controller that maintains the temp inside the heater zip pouch to a near-room temperature value. I was informed that the Escali scale works down to 40°F (4°C), hence the heater.

I also built a heater using an Igloo thermos with a similar temp control to melt the captured frozen snow/ice in the outer cylinder. I know that I could simply bring it into the house, but I want to avoid traipsing a lot of snow inside. With the heaters, I can do everything out in the garage and just bring my notepad page with the data inside to report the precip.

My outer cylinders weight in at between 459 and 462g. I placed a Brother label on each so I know the weights as I rotate through the three different cylinders. I haven't been reporting daily cores recently, and almost never do an overall total depth core sample.

I bought a second Escali scale for instances that there is a lot of snow/ice capture so I can weight it inside the house. I don't do this very often, but I like having the option in extreme cases where it is going to take a very long time to melt the snow/ice in the cylinder.

Greg H.

PaulMy:
Thanks Greg,
What is the benefit of the official Escali scale?
I just picked up a cheap $10 scale at local CT and it is to 0.5 gm precision.  1 gram = 0.126 mm so 0.5 gm = 0.063 mm and that is lower than the 0.2 mm precipitation used for metric reporting, so the scale's 0.5 gm increment is well within the reporting rounding.


I have 2 locations with the mounted outer tubes and sometimes have a variance of 0.4 mm between them depending on rain intensity and wind.  Surprising for snow these are generally the same SWE.

I measure new snow every snow fall morning and report the SWE, (but not to the 0.1 cm precision asked by CoCoRaHS as that is not possible to see that accurate).  I also measure and report total snow on the ground every day, but do the core sample usually only on Mondays.

I have 5 outer tubes so I can replace the mounted locations immediately if it is snowing while doing the reading, and use the other for core sampling.  The 3 original tubes from 2014 and 2015 weigh 457, 458 and 459 gm. empty, and the 2 new recent ones 451 and 452 gm, and they all came from CoCoRaHS Canada vendor.

One thing that bothers me is that I try to follow the CoCoRaHS practises for accuracy and report to 0.2 mm precipitation and cm snow but CoCoRaHS then seems to convert to Imperial and back to metric which most often then shows a 0.1 mm plus or minus.  All metric reporting is in 0.2 increment. The attached shows my report submission this morning of 0.4 mm precipitation but on the map as 0.5 mm and then when I go back to my entry page it is changed there as well.  Only once in the last 7 days is the CoCoRaHS details and map showing the actual submitted report.

Maybe I should complain to CoCoRaHS instead ](*,)

Enjoy,
Paul

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