Topic: New Climalytic TROPO gauge installed

[Cutty Sark Sailor]

The only reason I asked is because they say it's more accurate. For $100 I would like to see what those results are. 

https://www.youtube.com/watch?v=XWge9wWPzKk

[WheatonRon]

I am no longer going to post the gauge readings here, but I will continue to show the Stratus readings in my daily comments on CoCoRaHS.

https://www.cocorahs.org/ViewData/ListDailyComments.aspx

Enter MI-PI-1 in the Stations Fields box and tick the Station Number box.

Greg H.

I would call your recent results of the new Tropo gauge and the Stratus gauge statistically insignificant. Not worth $100.

[miraculon]

All four of my gauges agreed this morning!

The two TBRs: Davis VP2 and Novalynx 8" indicated 0.06"

The TROPO and Stratus both agreed with 0.06"

I think that this is the best agreement between gauges that I have seen here. The wind was very light over the past 24 hours, so it must have been straight down.

Greg H.

[CW2274]

Not to be a turd in your rain measuring punch bowl, but 0.06" is hardly a meaningful sample size. Personally, I look for at least half an inch or so before I get what I feel is a good comparison. Getting four gauges to agree at any given time with a decent sample size is an anomaly.

[miraculon]

Today's measurements. Intense downpour yesterday afternoon around 3 PM.

TROPO indicated 0.83"

Intense rain yesterday afternoon between 1450 and 1515. Reported rain from TROPO. VP2 (TBR) reported 0.89" Novalynx (8" TBR) indicated 0.88". Stratus had 0.88".

Much wider variation than the prior measurement, CW2274. This is more typical.

TROPO does seem to come out lower than the other gauges in general. It could be location in the yard. The behavior of the TBRs during heavy rain could also be a factor.

Note that I have a small yard and the gauge locations are not compliant with the siting recommendations in terms of distance to buildings. Not much that I can do about it other than move.

Note that I had applied the special polycarbonate-type RainX in the morning prior to the rain event.

Greg H.

[ValentineWeather]

This morning's rain readings:

TROPO was 0.17"

Stratus gauge had 0.20"

TBR gauges: VP2=0.18"; Novalynx=0.21"

The prior rain event had closer results, so this is probably normal variability. I'm going to contact the Climalytic folks and see if RainX or Plexus is OK on their plastic. There are notably more clinging drops in the TROPO funnel and inner measuring tube.

Greg H.

This is what I'm seeing too Greg. About (-.07") per inch low vs 2 different 8" gauges the Novalynx and NWS 8" SRG. I've been testing now since the gauge came out and have had a lot of rain. Events with any wind I don't count but this rain (.35) was almost no wind and light rain coming up (-.02") low.  Somethings wrong.

I have correspondence with someone else seeing something similar.

I did fire an email off to Cocorahs Friday but got no response as of yet.  I find it concerning myself to allow a new gauge with the official tag, that runs 5-7% low. It's an easy fix just come out with an inner measure tube that's to the correct scale needed for accuracy. It's a little less than a true 4"  diameter may be the scale issue.

For those with the original Cocorahs gauge, there is a fix for splashout on heavy downpours which they do experience. Just get a spare second top/funnel and cut it out. Then glue it on top and you've doubled the funnel depth.   

[Cutty Sark Sailor]

You folks receive the last Climalytic Newsletter?
Have you actually done the 'measurements' by weight and volume?
excerpt
Is The TROPO Accurate?
Some people have become concerned about the fact that their TROPO gauge frequently reports less rain than their Stratus gauge. To help remedy these concerns, we’ve produced a video that features three experiments that test the accuracy of both the Stratus and the TROPO. Please watch the video, and follow along with your own gauges if you’d like!
 
For those that don’t have time to watch, we found that while it initially seems like the TROPO has a low bias of ~3%, it’s actually the Stratus that has a high bias of ~3%.
 
A recent CoCoRaHS blog summarized the TROPO by saying, “The TROPO gauge incorporates many suggestions made by CoCoRaHS observers over the years for improving the overall gauge. One key difference - it IS more accurate than the Stratus gauge, and it was designed that way. We know the Stratus gauge over-measures rainfall by about 2.5%, and the TROPO gauge does not have that error.”

I had confirmed this myself during field testing, and with the Tropo production version.  Variance partially depends on which production run of Stratus you may have.
With very minor variations due to temperature and purity, 1 inch water in 1 inch dia cylinder should weigh 206g and with a 206ml volume. (ok, 205.97 or whatever...)

The right hand column is the amount Tropo measured against 1 inch line of various Stratus cylinders.
You'll find the % results similar down to about a half inch.  Didn't document lower volumes.
This was against the 'pre-production' release version, which is slightly different in features and appearance.
I have run the same tests, same cylinders, on my 'release' version and the results are virtually identical.
My tests  use / compare (with) graduated glass lab cylinders, (volume) and digital scale (weight).

I'd also noticed excess moisture on Tropo inner cylinder, and it's funnel.  I'm sure this is often condensation.  There appears to be less evaporation from the TROPO, it is 'tighter'. Like you all, I notice extra moisture in/on cap, some I do know has been condensation droplets, but it is mostly precip that hasn't collected.  I note similar ' cap issue' with Stratus also, but less condensation.

[ocala]

Did a little experiment of own with an old early model coco gauge bought in 2008 and a new coco gauge bought in 2022. The new one is not the TROPO gauge.
Using the just the inner cylinder. Of note on the 2 cylinders I did make the overflow slot slightly deeper on both because when both were full they would read over an inch. Wanted them to read and inch exactly.
Old cylinder weight was 90G
New cylinder weight was 91G
Old cylinder weight with 1 inch of well water 286G
New cylinder weight with 1 inch of well water 293G
Did 3 different tests.
That's a big difference.
Going to mount the old coco gauge again on the same 4x4 where the new one is and the new Davis gauge just for comparison. Having a hard time dropping that much money on a  new TROPO gauge to see how it fares. 

[ValentineWeather]

When did we learn the stratus had a high bias? Something I've never experienced. I've done lots of side-by-side testing with the 8" Novalynx and the Stratus if anything it runs a tad lower provided the rainfall was significant say above a couple of tenths.  Yes, the plastic gauge may read a couple of hundredths when the metal 8" only reads .01 because of the wetting process needed on the larger metal gauge but that's expected.

When I received the Tropo I immediately was seeing a negative bias and not just a couple of events but this was over 8" of rainfall for the month of June so was able to get a good feel and average.

As mentioned before I'm seeing around (.07") per inch low vs the 8" SRG.  The difference was so significate I decided to get the actual Official NWS (SRG) to make sure it wasn't the Novalynx just reading high. So after several attempts was finally able to procure one of the now rare and hard-to-find original units with the heavy brass funnel and copper measuring tube. The good news is the Novalynx was not reading high after all and the two 8" gauges are identical provided the matching measuring sticks are used. Very good news for the folks at Novalynx I let them know also their gauge was accurate.   

Because I'd given all my original Stratus gauges away wasn't able to test that gauge directly against the Tropo. I did order a couple from the Cocorahs store online but haven't received them yet.  I'll continue testing the two 8" gauges along with the Stratus and Tropo once they get here.

[miraculon]

We had more than an inch of rain this morning, so it was my first experience with the overflow of the inner cylinder.

The overflow occurred exactly at the 1" marking. 
The white handle made it easy to pour the overflow back into the measuring cylinder.

Good on both counts.

It was tough to get a good measurement on four gauges during fairly heavy rain this morning.

TROPO: 1.10"
Stratus: 1.19"
Davis TBR: 1.28"
Novalynx TBR: 1.23"
TBR data for reference only.

I'll accept the high bias theory for Stratus, but the difference seems to be running much more than 2.5% 

Greg H.

[ValentineWeather]

As before I've personally never seen the Stratus run above the 8" SRG. Waiting for a new gauge to come in since I'm Stratus-poor after giving them to friends and went strictly with the 8" SRG. Why play around with the 4" when you have the real thing? The only reason I tried the Tropo was to see if the deeper funnel worked as expected and that's when I discovered the low bias of around (-.07") per inch. 

I spent the day getting ready for the side-by-side comparison which will be 4 different gauges. 2-8" (NWS and Novalynx) and the new Stratus along with the Tropo.
The reason I spent the day reconfiguring the gauges was so all were within a few feet of each other. The way I was set up prior there was about 16-18 feet separation and on different planes. So no excuses now. It either runs low or doesn't.

[miraculon]

As before I've personally never seen the Stratus run above the 8" SRG. Waiting for a new gauge to come in since I'm Stratus-poor after giving them to friends and went strictly with the 8" SRG. Why play around with the 4" when you have the real thing? The only reason I tried the Tropo was to see if the deeper funnel worked as expected and that's when I discovered the low bias of around (-.07") per inch. 

I spent the day getting ready for the side-by-side comparison which will be 4 different gauges. 2-8" (NWS and Novalynx) and the new Stratus along with the Tropo.
The reason I spent the day reconfiguring the gauges was so all were within a few feet of each other. The way I was set up prior there was about 16-18 feet separation and on different planes. So no excuses now. It either runs low or doesn't.

Cool, it will be interesting to see your results.

Greg H.

[CW2274]

Waiting for a new gauge to come in since I'm Stratus-poor after giving them to friends and went strictly with the 8" SRG.

I have two inner tube Stratus's not in use, but no outer cylinders or collection cones. One is 200 grams per 1.00", and one is 204 grams per 1.00" If you want the two inner tubes (or one, whatever) let me know, you can have them free, including shipping, as they're just sitting here collecting dust. I'm actually going to the UPS store tomorrow, if you want them, now would be the time. I'll still get them out later if you want as well.

[ValentineWeather]

Waiting for a new gauge to come in since I'm Stratus-poor after giving them to friends and went strictly with the 8" SRG.

I have two inner tube Stratus's not in use, but no outer cylinders or collection cones. One is 200 grams per 1.00", and one is 204 grams per 1.00" If you want the two inner tubes (or one, whatever) let me know, you can have them free, including shipping, as they're just sitting here collecting dust. I'm actually going to the UPS store tomorrow, if you want them, now would be the time. I'll still get them out later if you want as well.

Thanks, they got shipped out yesterday. It'll be here Monday. I'm still going to test the Tropo against the two 8" gauges in the meantime. I'll post those results too with images.  Tonight we should get rain 70% chance. 

[CW2274]

Very well. If you have the ability, I think we'd all like to hear how much water exactly one inch weighs. This discrepancy, I imagine, is the genesis of the Tropo.

[ValentineWeather]

Storm totals  (1.49") measured with the NWS SRG, the Novalynx measured (1.51") and the new Cocorahs Tropo did better than expected (1.42"). So (.07") low vs the NWS gauge so is running 4% low. This was a substantial rainfall almost 1.5" so a good sample size plus a low wind event 3-4 mph throughout so a good comparison test. The only thing different from the previous test was all gauges were on the same plane and closer together.

How the original Cocorahs would have faired I suspect slightly higher than the Tropo.
The airport ASOS weighing gauge measured (1.52").

[miraculon]

More consistent results with the rain yesterday after observation time.

TROPO=0.31"
Stratus=0.33"

TBR:
VP2=0.33"
Novalynx=0.32"

Greg H.

[Cutty Sark Sailor]

Very well. If you have the ability, I think we'd all like to hear how much water exactly one inch weighs. This discrepancy, I imagine, is the genesis of the Tropo.

Weight of one inch of water depends on the dimensions of a collector, temperature, and water quality.
With all the 'rounding' and conversions necessary, etc, it weighs slightly less than 206gms, in a 4" (10.16cm)  collection cylinder.

One inch of pure liquid water  at 70°F / 21°C in a 10.16cm inner diameter collection cylinder weighs ±205.52 gms.
A teeny bit more at lower temperatures. Less at higher temperatures. The density change is quite minor while liquid, however. Just don't freeze it or boil it.

With variables taken into account,  TROPO explains with 'rounded' 206gm, 206ml,...
Density of water: Choose your confusion factor at
https://www.usgs.gov/special-topics/water-science-school/science/water-density
or
https://www.aqua-calc.com/page/density-table/substance/water

For me, I choose:
water density at 70°F / 21°C =     0.99802gm/cm³
1 cubic cm = 1ml

1 Inch of Rain falls in  4" cylinder cap, with these specs:.
diameter 4"  = 10.16cm
radius     2"  = 5.08cm
and I desire to compute for 1in, or 2.54cm

Calculate Volume:  V= h × π × r²
diameter 4"  = 10.16cm
π= 3.14
r=5.08cm
h=2.54cm  (The  depth we want to measure)   
Volume= 2.54 × 3.14 × 5.08² = 205.85 cm³ 
ml=cm³  
Volume   205.85ml

Calculate Weight (mass)
Weight= Density × Volume
Weight= 0.998gm/cm³ × 205.85ml = 205.5gm

For simplicity, rounding volume to 206ml for a 4 inch collector.
and 205-206gms should equal one inch pure water from such collector. 

200 grams from a 4" inner diameter cylinder, by math, cannot equal one inch, regardless of what the 'measurement' cylinder says.

Then you apply math to inner  cylinder to determine its dimension and graduations.

And that can be tricky depending on production characteristics, including a taper radius to allow removal from any molding of cylinders, etc. Variations in water density, and purity, temperature and debris in collector, force everything to be in the ± and any given instance.

 So I conclude that one inch measuring cylinder, if truly one inch, should NEVER contain less than ±205.5 ml or gms.
This suggests to me that a 1ml tipping bucket should count 204-206 tips if exactly an inch falls into it.

[WheatonRon]

Bottom line? The guidance on the CoCoRaHS website is correct. When using the Stratus gauge, 206 grams equals 1 inch of water!

[Cutty Sark Sailor]

Bottom line? The guidance on the CoCoRaHS website is correct. When using the Stratus gauge, 206 grams equals 1 inch of water!

...except MY 6 Stratus tubes DO NOT equate 206gm to one inch indicated!

[WheatonRon]

...except MY 6 Stratus tubes DO NOT equate 206gm to one inch indicated!

[/quote]

Different issue. If you weigh the water in the CoCo gauge, absent the inner cylinder, deduct the actual empty weight of the large collector, 206 grams of weight equals 1 inch of water. The most accurate way to measure actual precipitation—summer or winter. Skip the inner cylinder. That said, leaving the inner cylinder in the large collector in the summertime is easier as long as the precipitation you are measuring is less than one inch. If not, pour the water from the inner cylinder into the large collector then weigh. I get rainfall exceeding an inch from a storm maybe twice a year—not a big deal.

[Cutty Sark Sailor]

...except MY 6 Stratus tubes DO NOT equate 206gm to one inch indicated!



Different issue. If you weigh the water in the CoCo gauge, absent the inner cylinder, deduct the actual empty weight of the large collector, 206 grams of weight equals 1 inch of water. The most accurate way to measure actual precipitation—summer or winter. Skip the inner cylinder. That said, leaving the inner cylinder in the large collector in the summertime is easier as long as the precipitation you are measuring is less than one inch. If not, pour the water from the inner cylinder into the large collector then weigh. I get rainfall exceeding an inch from a storm maybe twice a year—not a big deal.

Nope.  Seems like you're talking apples and oranges here, in a manner of speaking, or 'begging the question'.  Accuracy of visual observations using a supposedly accurate device has been the issue all along. You now nominate the 'weight' measurement method as the best way to determine volume, and I don't disagree... assuming it is collected in an accurate cylinder, the scale is accurate, etc. But that should be un-necessary in 'normal' daily reporting, if the inner measuring device / decanting receiver, were simply accurate. 

The new gauge kit provides an inner cylinder the DOES reflect better accuracy consistently, without bringing out another instrument (the scale) while disregarding that 'instrument module' of the original device which claims to indicate the accrued volume accurately... heck the 1" 'overflow' slot is all over the place from tube to tube in the older system, which should be an red flag for quality and consistency.

The shock factor seems to be that more accurate 'reporting' results in LOWER volumes than expected or than some other gauge may indicate.

[CW2274]

Very well. If you have the ability, I think we'd all like to hear how much water exactly one inch weighs. This discrepancy, I imagine, is the genesis of the Tropo.

 So I conclude that one inch measuring cylinder, if truly one inch, should NEVER contain less than ±205.5 ml or gms.

Then by that conclusion, the Stratus gauges we're never accurate, at least mine. I have four. Two measure 200 grams at the inch mark and the two newer ones at 204. This is tap water, not boiling or freezing, so temp is irrelevant. And if all remember correctly when this came up about a year ago, the seller found my conclusions spot on as he duplicated it. Just sayin'....

[Cutty Sark Sailor]

Very well. If you have the ability, I think we'd all like to hear how much water exactly one inch weighs. This discrepancy, I imagine, is the genesis of the Tropo.

 So I conclude that one inch measuring cylinder, if truly one inch, should NEVER contain less than ±205.5 ml or gms.

Then by that conclusion, the Stratus gauges we're never accurate, at least mine. I have four. Two measure 200 grams at the inch mark and the two newer ones at 204. This is tap water, not boiling or freezing, so temp is irrelevant. And if all remember correctly when this came up about a year ago, the seller found my conclusions spot on as he duplicated it. Just sayin'....

Yep. You certainly did.
 And a lot of us duplicated the same issue. Actually, it goes back even further than a year ago. It's been known for a LONG time that the measurements of similar gauges were hit or miss depending on production.  I had quit trusting my Stratus build years ago, the issues were so obvious for many of us, but it was the 'standard' and the only approved gauge for CCR other than the NWS 8" (Rolls Royce priced, if available) gauge.

[WheatonRon]

I guess we should be happy that the Stratus gauge is for hobbyists, not for heart surgery or transplants.