Topic: New Climalytic TROPO gauge installed

[ValentineWeather]

Had a thunderstorm last night with wind, 53 mph gust at the 26-foot height and this is what rain gauges recorded. 
The NWS 8" SRG measurement (.83"), The 4" Stratus, and this is the latest model (.81") or (-.02%) low and within the +/-4% criteria Cocorahs allows for gauge error. And the new 4" Tropo fell way under again (.77"). or (-7%) low.
So I've had 3 rains where it was 7% low and 2 rains 4% low and several smaller rains where it wasn't low at all so similar to what Jerry was reporting. 
My Stratus does have the double cap with the top funnel hacksawed out. It makes a difference with heavy downpours and helps prevent splashout. This may be what the Tropo needs too, a deeper funnel.

What counts is how a rain gauge performs under real conditions and from what I've seen falls short. Wherever they tested this gauge, I'm told (Colorado) apparently they had nice light rains but that's not real-world conditions. I'm just giving the information as it occurs and a possible solution (deeper funnel). I'll attach images.

[openvista]

This is what my comparison shows, i did some static comparisons indoors are the results are like you show but the real test is the ability to accurately catch the rainfall with all rates of rainfall and winds. The tube can be really accurate in showing 1 inch but if the gauge is having trouble with the catching of rain do to various conditions, that is the real test. If the gauge has trouble in heavy rains then the catch not the tube is showing an error. I use my eight inch gauge because it performs much better and is more accurate than the four in gauges. The tropo has shown to be accurate with light to moderate rainfall and compares to the eight inch quite well but with heavy rain it suffers the same as the Stratus. My stratus would under count in heavy rains too but with the added cap to deepen the funnel and prevent the funnel from filling up and causing splash out thus lower reading. In heavy rain the funnel fills up faster than the water drains into the tube causing the lower reading than the much larger funnel of the eight inch which has a larger opening for the water to drain faster. This is just what i have seen so far and will continue to do comparison in various rain events.

From everything that's been admitted by CoCoRaHS and verified here, the Stratus 4" gauge does not catch more precipitation in windy events. It reports more precipitation, thus making it preferable to some here who compare it to the 8" SRG.

You can modify the funnel of the Stratus and catch more rain in heavy rain events, but it will still report higher than it should based on what it actually collected.

A high wind precipitation event will show ANY 4" gauge to be lacking compared to an 8" SRG (mounted lower due to its stand therefore catching more precip since wind is less of a factor near ground level). This tendency applies to the Tropo as much as to the Stratus. Aperture (opening) size and mounting height matter.

[openvista]

Had a thunderstorm last night with wind, 53 mph gust at the 26-foot height and this is what rain gauges recorded. 
The NWS 8" SRG measurement (.83"), The 4" Stratus, and this is the latest model (.81") or (-.02%) low and within the +/-4% criteria Cocorahs allows for gauge error. And the new 4" Tropo fell way under again (.77"). or (-7%) low.
So I've had 3 rains where it was 7% low and 2 rains 4% low and several smaller rains where it wasn't low at all so similar to what Jerry was reporting. 
My Stratus does have the double cap with the top funnel hacksawed out. It makes a difference with heavy downpours and helps prevent splashout. This may be what the Tropo needs too, a deeper funnel.

What counts is how a rain gauge performs under real conditions and from what I've seen falls short. Wherever they tested this gauge, I'm told (Colorado) apparently they had nice light rains but that's not real-world conditions. I'm just giving the information as it occurs and a possible solution (deeper funnel). I'll attach images.

There's a simple way to bypass splash out error: remove the funnel and inner cylinder altogether before the storm hits. Then after the storm is complete use a scale to weigh what's in the outer cylinder in grams, subtract the weight of the empty outer cylinder (again in grams) and divide by 206. This will eliminate any potential bias in either of the 4" gauges we are discussing. Now compare that to what fell in the 8" SRG during these same windy events. The shortcomings of a 4" gauge (including the Tropo) should then become apparent over time.

Obviously such an experiment will not compensate for siting discrepancies. YMMV.

[Cutty Sark Sailor]

whatever bounces out, blows out, doesn't fall, into or through, the collection funnel...
is begging this specific question:
Is the indicated measurement an accurate indication of the amount actually in the gauge?
Hell, add variations and computations for 'with bird spikes' / 'without bird spikes' -- Winds East, Winds West, ground level vs 30", 40° vs 100°... etc

The Tropo is mathematically identical to the 8" NWS SRG.  NOT another brand or Name 8" gauge. The Stratus CCR 4" gauge is NOT another brand name 4" Gauge.   Prior to this spring, the Stratus produced and the SRG were the ONLY 2 approved gauges. 
The Stratus indicates one inch at ±201gm, ... Therefore, at best, the Stratus is NOT a 4" calibrated rain gauge...

The 8" Official SRG WILL, or should,
at 70°F or 21°C.   one inch:
Weight= 0.998gm/cm3 ×823.7ml = ±822gm
Mathematically that should be is 4 X the TROPO 1" mass
±205.5 times 4 equals ?
... 'with bird spikes' / 'without bird spikes' -- Winds East, Winds West, ground level vs 30", 40° vs 100°... etc ... same number of equal size drops in each must be same volume/mass.
IF the 'catch cap' is precisely 4" diameter, and 1 inch of precip falls into it, then  it collected 205.93ml.
Using average H2O density as 1.0gm/cm3, then:
One inch MUST equal the 205.93± gm mass (206) (temp etc not withstanding).
(70°F, 21°C):  (Weight= 0.998gm/cm3 × 205.93ml = 205.5gm)
 If it is an 8" collector, then one inch = Calculate Weight (mass)
Weight= 0.998gm/cm3 ×823.7ml = 822.05gm

[openvista]

Is the indicated measurement an accurate indication of the amount actually in the gauge?

...

The Stratus indicates one inch at ±201gm, ... Therefore, at best, the Stratus is NOT a 4" calibrated rain gauge...

^THIS

To the extent that observers continue reporting what the Stratus inner cylinder indicates, they are reporting an over measurement to the public. That is not the amount that actually fell in the gauge, regardless of workarounds.

Ironically, modifying the cap for greater capture during high intensity events may make the high bias even more pronounced. The splash out would otherwise somewhat subtract from the high bias over time. That's what the 10 yr comparison study I posted earlier found.

[CW2274]

Well, I thought I'd stir the pot here with today's lovely, sometimes wind driven rain. Comparison of two Stratus's, and two hand calibrated (by me) 8" RW tippers.

Older Stratus inner tube... 200 grams = 1.00" of rain...    0.70" measured.

Newer Stratus inner tube... 204 grams = 1.00" of rain...   0.69" measured.

RW tipper #1.... 0.74" measured.

RW tipper #2.... 0.73" measured.

Give or take, this is a typical result that I've seen when it rains enough to get something meaningful.

This concludes this evening's pot stirring.

Let me help muddy things. Somehow, both my RW tippers were reading 4% too high. Don't even get me started on how this came to be, I'm super anal about my calibrations. Anyway, those RW measurements now turn into 0.71 and 0.70. Obviously now more in agreement with the two manuals. I'm going by the 801 grams that RW says is one inch for their tipper.

Have a nice day.   

[miraculon]

This morning I had 0.44" in the TROPO and 0.48" in the Stratus.

I decided to use the weighing method. I weighed everything with the captured rain (tube, funnel and strainer) at 887 g. This included any water retention in the funnel and strainer. I dried the outside of the outer cylinder.

Emptying out the inner cylinder, the total mass was now 788 g. Subtracting this from the total of 887 g, results in 99 g. Divide by 206 and I get 0.48", which happens to match the Stratus, regardless of the high bias allegations.

So, the cumulative droplets in the funnel area and strainer accounts for 0.04". I know that CoCoRaHS doesn't recommend strainer screens, but I don't like dealing with the bugs and other debris. I did spray the funnel with the plastic RainX recommended by Climalytic.

I'll have to ponder running the TROPO sans strainer (Danco). I know that the clinging droplets in the Stratus outer cylinder account for about 0.01" when used without the measuring tube and funnel. This is more surface area than the funnel of the TROPO. Maybe I'll try to get the strainer wet weight and compare it with the dry mass of 19g, then calculate the amount of rain held back.

Has anyone else ran any tests/experiments of strainers? And surface retention for that matter.

I think that the TROPO is better than initial results were indicating. If the strainer is the main culprit here, that's my own fault. All of the rain just isn't making it into the measuring tube... 

Greg H.

[ValentineWeather]

 I did decide to give the Tropo one more chance after taking it down, I keep hoping for different results so put it back in service perfectly leveled on the same plane as other gauges all within 6 feet of each other. The heavy rain event had light wind, our peak gust throughout was only 18 mph at 26-foot height. 

Results: The real McCoy, standard NWS 8" gauge (1.27"), Stratus (1.25") so low 2% and the Tropo (1.20") low 6%. I used my finger and got as many droplets as I could to drain down into the inner measuring tube.

Took the Tropo back down. The definition of insanity is doing the same thing over and over and expecting different results.

[WheatonRon]

I did decide to give the Tropo one more chance after taking it down, I keep hoping for different results so put it back in service perfectly leveled on the same plane as other gauges all within 6 feet of each other. The heavy rain event had light wind, our peak gust throughout was only 18 mph at 26-foot height. 

Results: The real McCoy, standard NWS 8" gauge (1.27"), Stratus (1.25") so low 2% and the Tropo (1.20") low 6%. I used my finger and got as many droplets as I could to drain down into the inner measuring tube.

Took the Tropo back down. The definition of insanity is doing the same thing over and over and expecting different results.

Thanks Randy. You have saved me $100 why I shouldn’t get the Tropo. I have 2 Stratus gauges and accept there will be always differences—its the nature of the beast, so to speak. The other day, I put both gauges out in the open with few trees and omitted the funnel and inner tube. After a storm with average wind sitting right next to each other, one Stratus captured .54 and the other .51. Each Stratus was weighed (in grams) with the rain water, I deducted out the actual weight of the gauge itself (each gauge has a slightly different empty weight) and divided by 206. I was surprised with these results, but not overly so.

[miraculon]

More info, per today's comments on CoCoRaHS:

Davis VP2=0.04"; Novalynx=0.03"; Stratus=0.03". Start/Stop times from Hydreon data. Rain measurement reported is from TROPO gauge. Note: retained water in funnel and strainer measured by weighing wet funnel/strainer at 158g vs. 154g. 4/206=0.0194", approximately 0.02". Add this to tube measurement of 0.01", equals 0.03" matching Stratus gauge. So an adjusted rain at TROPO location would be 0.03" matching Stratus gauge. I will continue to monitor and develop an adjustment scheme after I accumulate more data.

I'll need to repeat this again to determine "typical" water retention in the funnel and screen. According to measurements of wet/dry mass of the funnel/spikes/screen the net difference is 4g. Dividing out by 206 results in 0.0194" retention or almost 0.02". The screen itself account for 3g of this total retention. This would be 0.0145" just in the screen.

I'm going to remove the screen and see what happens. As a side note, the 8" Novalynx TBR has a Danco screen installed in the funnel.

Greg H.

[thomas]

How accurate is good.  Some years ago I use to get hired by an insurance company to take a rain gauge to outdoor concerts.  Promoters would buy rain insurance and back in the day it would be a good six figure payout.  It was a nice gig as you would be back stage with all the celebs.  I remember a Beach boys concert where we had a on and off light rain.  The striking point for the payout was .25 of an inch.  By the end of the concert I had .23 in my 8 inch gauge. The funnel had a lot of drops on it (fallen rain) and the promoter was constantly checking in for rain totals.  There was no wind but if you blew on the funnel the water droplets would get measured.  Not sure what happened but my final total was .26 and the promoter got his money.  A rep from the insurance company was also present watching how things developed.  In this case a different rain gauge could provide a big difference in payout.

[openvista]

Emptying out the inner cylinder, the total mass was now 788 g. Subtracting this from the total of 887 g, results in 99 g. Divide by 206 and I get 0.48", which happens to match the Stratus, regardless of the high bias allegations.

Did you also weigh the Stratus? Because if you did, you eliminated the high bias which comes from reading the Stratus' inner cylinder. It is marked inaccurately.

That high bias can be reduced in a heavy rain storm by the Stratus' shallow funnel which causes drops to deflect out of the funnel. So depending on the nature of the precipitation event, you might have just broken even by happenstance.

I still have Stratus gauges around. I have thrown out the inner cylinder and just use the outer cylinder without a funnel cap. If you weigh it and use the proper denominator (206), it's just as accurate as any other 4" gauge (especially if you also only use its outer cylinder). Obviously, in warm summer conditions, evaporation becomes an issue without a cap.

EDITED 5:00 PM 8/15 to remove redundant sentence.

[miraculon]

Emptying out the inner cylinder, the total mass was now 788 g. Subtracting this from the total of 887 g, results in 99 g. Divide by 206 and I get 0.48", which happens to match the Stratus, regardless of the high bias allegations.

Did you also weigh the Stratus? Because if you did, you eliminated the high bias which comes from reading the Stratus' inner cylinder. It is marked inaccurately.

That high bias can be reduced in a heavy rain storm by the Stratus' shallow funnel which causes drops to deflect out of the funnel. So depending on the nature of the precipitation event, you might have just broken even by happenstance. Obviously, in warm summer conditions, evaporation can become an issue over time without a cap.

I still have Stratus gauges around. I have thrown out the inner cylinder and just use the outer cylinder without a funnel cap. If you weigh it and use the proper denominator (206), it's just as accurate as any other 4" gauge (especially if you also only use its outer cylinder). Obviously, in warm summer conditions, evaporation becomes an issue without a cap.

My objective was to determine the water mass of retained droplets in the TROPO funnel and strainer.

I have the empty mass of all my Stratus outer cylinders, but this is used for scale measurements of the snow catch in the winter.

Greg H.

[Cutty Sark Sailor]

Experiments and measurements...vs assumptions and eyeballs. I DO have issues getting consistent decimal points, but here's some conclusions from rough draft notes.
 'MV'  used for simplicity, since pure H₂O has miniscule density variations at temp.
If we go with the reference '1' for density,  then grams, milliliters, cm³ (cc), etc all will have the same 'number'. I just don't fool with showing the conversion to 'inches'...
4"cylinder, 1" deep, 4°C  (39.2°F) pure H2O = 205.96MV
volume=H×π× R² = 1 × 3.14 × 4 = 12.57 cu.in. = 205.93 cc = 205.93ml = 205.93 gm (205.93MV)
NOTE: An 8x1 cylinder MV should be EXACTLY 4 times the MV of a 4x1 cylinder.  The radius of the 4” is doubled, so H×π×(R2)² .
 Does 201gm = 1”, or does 206gm = 1”?  The answer can be YES for both queries... heh... .

 ‘Mass/Volume’.   

IF I ‘weigh’ my liquid, I MUST FOLLOW THE MATH for ‘cylinders’, and the density of water, related exactly to the size of the collection vessel. 800gm from an 8” collector is NOT the same as 800gm in a 4” collector! However 800gm in an 8” IS the same as 200gm in a 4”. Assuming the dimensions are in fact accurate at the cylinder mouth. 

QUERY: Variations in observations must be related to exact size of 'collecting' cylinders?  And/or calibration of visual indicator 'magnifying' cylinders?


Collecting:  STRATUS
Now, One of my Stratus (4”) cap inner diameter was so low, I simply didn’t trust the caliper inside measurement (averages), 3.952±.... so to convince myself,
I made a wax cast of the  lip... attachment 1. Yep, that’s significant because if I assumed it was 4 inch gauge, I’d be incorrect. This 3.952 cylinder can only MV 200.96 / inch! IF the inner cylinder it feeds indicates 1” that will be fine. As long as I keep the cap and cylinder as a ‘set’.

 BUT my Stratus inner cylinders are all over the place at 1” MV:
(a)200 (b)201 (c)202 (d)198     So with THIS ‘Stratus Sm’ cap, the selected inner cylinders would variously:
(a)over-report , (b)accurate, (c) under-report,  (d)over-report! 
And if I use my 3.981± Stratus cap with ANY of those 4 inner cyls, at  1”it will drop  203.97MV, and... all 4 inner cylinders, would over-reportvisually!

Furthermore, if I was reporting using 'weight' method,  AND if I were using 201gm/inch, I'd 'over-report', and if I were using '206gm/inch' I'd Under-Report! 
---
Assuming my 4” outer cylinder is 4”, and my digital scale says 205.96 gm, I have an inch of precip.  No problem.
BUT 1” of rain = 205.93 (206) gm in a 3.956 cylinder is NOT valid.
ALL MY stratus outer cylinders are virtually (averaging) 3.956±.  BUT ONE INCH ain’t 206gm!
h ×  π × r² = 1 × 3.14 × (1.678)²= 201.42MV ... 
SO DOCUMENTS WHICH STATE “201gm” in Stratus outer cylinder would be correct,±.  Using 206 would be incorrect for the Stratus!
           ----------------------
TROPO
I've 2 Tropos, one is production series, one is a field test version (differences are mostly cosmetic, dimensions are identical)  BOTH the CAPS, INNER CYLINDERS, and OUTER cylinder dimensions match exactly between the 2 versions.

206gm would be correct for a TROPO cap! (Actually, 205 might be a tad more accurate based on my measurements)
Those 'caps' are ±3.988± avg around the rim.

..the math says that a 3.99” diameter cylinder, one inch in depth, with water at 4°C or 39.2°F with a density of 1, will MV 204.9.
 (Result depends on how you round the numbers)
For this, within miniscule decimals, the caps are identical... and other ‘constants’ are... ...constant..
In fact, BOTH my Tropos indicate 1 inch right at 205± MV.
   
 

[openvista]

Cutty Sark Sailor,

I have 3 Stratus outer cylinders. When I measure the inner diameter at the score/seam marks I see that they all measure EXACTLY 4.0". I have a scientific ruler marked to 1/32". So the proper denominator for determining precipitation by weight in grams would be 206 in all 3 cases not 201.

When my inner cylinder (I only have one) indicates 1.0" of water using the score marks the weight (minus the inner cylinder dry weight of 91 g) is 202 g. 

When I use the same (CoCoRaHS-approved) scale for the TROPO, 1.0" indicated in the inner cylinder equates to 206 g (minus the inner cylinder dry weight of 123 g).

Measuring the TROPO cap I find it's exactly 4.0", same as my three Stratus outer cylinders. The TROPO outer cylinder is tough to measure because of the spout and lack of scoring.

There appears to be no bias in my TROPO inner cylinder paired with the cap. Whether the TROPO cap leads to splash out I cannot say.

I am not trying to say that there have not been Stratus manufacturing variances in the past that led to varying outer cylinder widths. But my 3 outer cylinders, which were all acquired from WeatherYourWay (CoCoRaHS official supplier) between approximately 2015 and 2020, are consistent in size.

---
EDIT: The one Stratus cap I have does appear to be 3 31/32" across (1/32" short of 4"). It's harder to measure because it lacks score marks. When I deploy the Stratus, I don't use the cap since I don't use the inner cylinder.

EDIT 2: So if my cap is paired with my inner cylinder then the proper metric weight denominator should be 202.72 (rounds up to 203 g).

Here's my math using the cap as the capture radius (3.96875" = diameter):

volume (cu inch) = height (1") x pi (3.14159) x radius squared (diameter halved^2)
volume (cu inch) = 1 * 3.14159 * (3.96875/2)^2
12.3707 cu inch = 202.72 mL (1 cu inch = 16.387064 mL)
202.72 g (1 mL = 1 g)

[Cutty Sark Sailor]

You define exactly the issue: Stratus inconsistencies.  Yep, I don't have a scientifically accurate 'caliper'.  AND the measurement MUST be at the LIP TOP... NOT down in the cylinder! That's the actual 'collector' diameter... anyway I can't claim your precision...
BUT:
see this attachment.
OOPS: forgot to add THIS note from my draft, pertinent to this attachment:
 I applied more diligent comparisons at low volumes, from 0 to ±0.25" the two types tracked pretty closely....
...then they begin to diverge ... It is REALLY noticeable at 0.4.
So some more math indicates that  0.4” must be 81.96 MV .. ok, call it 82 MC... .
 
ONE POSSIBILITY:
Climalytic says that the Tropo inner cylinder is tapered to facilitate release from the injection mold.
That taper is computer/laser calibrated to imprint the gradual spacing of the measurement lines, and is done AFTER the fabrication.
Looking at my Tropo inners, I can begin to see the graduation adjustments at about "0.3".
And the math at various ‘marks’ indicates they follow the MV computations for those several marks I checked.
 The STRATUS apparently DOES NOT taper, OR doesn't allow for the taper in the graduations. And it does NOT consistently follow the MV computations, and varies from tube to tube, at least in my collection.
Whatever...
The Stratus consistently begins noticeable over-reporting around the 0.25 mark.
Period.
 

[openvista]

You define exactly the issue: Stratus inconsistencies.  Yep, I don't have a scientifically accurate 'caliper'.  AND the measurement MUST be at the LIP TOP... NOT down in the cylinder! That's the actual 'collector' diameter... anyway I can't claim your precision...
BUT:
see this attachment.

I wouldn't question your measurements at all. As for my "precision"... the Stratus cap measurement is difficult, but nowhere does it measure 4".

I think the measurements you've posted should prompt everyone to measure, to the extent they have the tools to do so, the various components of their Stratus gauges before telling anyone that they are accurate.

[Cutty Sark Sailor]

Exactly... that's the whole point... BTW... See the addition I forgot to add to my last post...and stuck in a moment ago... .
This is a 'work in progress' for all of us, actually.

[Cutty Sark Sailor]

BTW ... Tropo on sale through end of year.... $59.99
https://store.climalytic.com/tropo-gauge/
Counting the field test, I've deployed the Tropo now for about 11 months.  Only peeve I have, with these tired old eyes, is the 'production' release (black)  engraving is a bit difficult to read in darker hours,  especially at the 'low end'...  probably due to clarity of cylinder material and sharpness of the imprint... my field test had frosted 'white' laser engraving, and it's much easier to see with flashlight, etc.  NO imperfections have developed in the cylinder material, still crystal clear....  Nice also that the cylinder materials still show NO, or virtually NO meniscus curve-- 

[miraculon]

Nice also that the cylinder materials still show NO, or virtually NO meniscus curve-- 

I have noticed this as well. Applying Plexus on the old Stratus helped eliminate the meniscus, but it isn't needed on the Tropo. Nice and flat.

Also nice that the overflow of the inner cylinder occurs at exactly one inch.

I think with the price reduction, the value proposition for the Tropo has improved. I purchased a spare outer cylinder for the winter. Interestingly, the mass was exactly the same at 512g, whereas the Stratus cylinder seem to be all over the map...

I just need to remember to divide the measured mass by 206 instead of 201.

Greg H.

[WheatonRon]

BTW ... Tropo on sale through end of year.... $59.99
https://store.climalytic.com/tropo-gauge/
Counting the field test, I've deployed the Tropo now for about 11 months.  Only peeve I have, with these tired old eyes, is the 'production' release (black)  engraving is a bit difficult to read in darker hours,  especially at the 'low end'...  probably due to clarity of cylinder material and sharpness of the imprint... my field test had frosted 'white' laser engraving, and it's much easier to see with flashlight, etc.  NO imperfections have developed in the cylinder material, still crystal clear....  Nice also that the cylinder materials still show NO, or virtually NO meniscus curve--

Thanks for the price alert. Free shipping too, at least in the US. I just ordered one. This product was over priced when released earlier this year. This price change makes sense and makes it competitive with the Stratus gauge. That said, this gauge will receive limited use by me as winter approaches—probably why the price drop. However, I can use it this winter for testing when the temperature/snowfall levels cooperates.