Topic: New Pro2 parts question

[Flag]

Since when does rainfall "swirl" through the funnel? This is "rainfall" not the garden hose or the over excess use of a calibrator!
 

Well excuse me! I find your responce a little rude and disrespectfull. Let me restate, when you first setup the station, you test the rain gauge by pouring water into it.

Do you? Some might, others might simply manually tip the buckets a few times.

So what has that got to do with "rainfall" and "swirling", absolutely nothing! And nothing to do with being disrespectfull what so ever. Lets keep in the reality zone here.

[neondesert]

Since when does rainfall "swirl" through the funnel? This is "rainfall" not the garden hose or the over excess use of a calibrator!

Someone correct if I am wrong but lets say at a rate of 60mm/hour which is quite heavy rainfall, that equates to 1mm/minute which for a 0.2mm tipper is 5 tips/minute or 21.3ml. Now 21.3ml (even double that 42.6ml @ 120mm/h) poured into the funnel over 60 seconds will not "swirl" and lets be realistic about this.

Actual rainfall falls on all sides/areas of the cone and not a single so called pouring point and I find this whole concept that the debris screen prevents "swirling" and affects accuracy quite frankly nonense. 

Just a guess might be the same wind that blows the screen out that could cause the bucket to tip the screen might break up the turbulence or the air rushing down the hole. That my non scientific guess. 

I agree mmorris.  There are numerous factors that influence the accuracy of a tipping bucket gauge (or any type of gauge for that matter) with siting being the most significant.

What this really all boils down to is: ensure you have chosen the best site you can, install the gauge properly per the manufacturers instructions, calibrate if necessary and keep it clean.

Finally, after all is said and done, accept the fact that your location may not be optimal and that a tipping bucket gauge is not going to deliver the most accurate results.  The readings may be spot on with a
manual gauge for one rain event and way off for another.  Debris screens, "anti-swirl devices", wind screens etc. are the least of your worries.  The device itself is, by design, less accurate than other gauge types. 
That said, for the purposes of our hobby, IMHO they do quite well.

For anyone interested, I'm providing a link to a MetEd webcast on the subject of rain gauges:
http://www.meted.ucar.edu/qpf/rgauge/

Rain Gauges: Are They Really Ground Truth?
This site provides a Webcast on issues associated with rain gauges presented by Nolan Doesken, Assistant State Climatologist at the Colorado Climate Center at Colorado State University. In his Webcast, Nolan comments on several issues surrounding the accuracy of rain gauges and what factors to consider when evaluating rain gauge data, including ASOS gauges.

You have to sign up first to listen to the webcast, however MetEd is FREE and is an excellent resource for anyone interested in weather.
Well worth the two minutes it takes to sign up! 

[Skywatch]

Since when does rainfall "swirl" through the funnel? This is "rainfall" not the garden hose or the over excess use of a calibrator!
 

Well excuse me! I find your responce a little rude and disrespectfull. Let me restate, when you first setup the station, you test the rain gauge by pouring water into it.

Do you? Some might, others might simply manually tip the buckets a few times.

So what has that got to do with "rainfall" and "swirling", absolutely nothing! And nothing to do with being disrespectfull what so ever. Lets keep in the reality zone here.

Of course you tip it to find out it has 0.01 increments, doesn't really evaluate accuracy. Isn't it much more accurate to take a graduated container full of a known volume pour it in and see if the readings come close to the known amount you poured into the funnel?
Same with the Rain to garden hose. No rain storm is going to flood the funnel like that. But in debunking a discussed scenario only proves that of a common theory. And that is the little plastic part is useless to which I agree upon against others that say this part stops whirlpools and straitens the flow to produce a much more accurate reading. That's the whole basis of this debait. Now you get 2 guys with one opinion 2 guys with another opinion. Unless they come to an agreement, a conflict is created until differences and compromises are made and truce is called. Usually this requires facts to backup each theory and opinion. One side shorter than the other, the comprimise is made and the arrgument is fixed.

[Flag]

Of course you tip it to find out it has 0.01 increments

Simply tipping will not show what the increments are as one tip is simply one tip, the increment is related to the counter weight AND the software configuration AND rain calibration#.

Isn't it much more accurate to take a graduated container full of a known volume pour it in and see if the readings come close to the known amount you poured into the funnel?

Poured in the funnel! Definately not but a known amount of water dripped over a long  period of time will indicate accuracy plus a few other things. I generally run 425ml for metric 0.2mm buckets over about 1 hour which "should" equate to around 99 tips (~ 20mm) if all is as expected. Of most interest is simply the number of tips and for measuring this I use an old WMII console.

As for facts well I am really interested in how even 100ml can be evenly put through a Davis VP2 rain collector over 1 minute and create any form of swirling, it's not going to happen, try it.

Now the other more important thing with the VP2 rain collector is to check the exit orifice of the hole just above the buckets as until recent times the this was usually jagged, ragged and uneven from the moulding process. All cones should be checked for this as this definatley could cause deflection of water to one side on exiting the bottom of the cone. Fix is a small fine single cutting countersink and rolling in the fingers only lightly remove any burs.

In saying that most of the newer cones are not bad and especially a lot better than the older ones.        

 

[Skywatch]

Of course you tip it to find out it has 0.01 increments

Simply tipping will not show what the increments are as one tip is simply one tip, the increment is related to the counter weight AND the software configuration AND rain calibration#.

Isn't it much more accurate to take a graduated container full of a known volume pour it in and see if the readings come close to the known amount you poured into the funnel?

Poured in the funnel! Definately not but a known amount of water dripped over a long  period of time will indicate accuracy plus a few other things. I generally run 425ml for metric 0.2mm buckets over about 1 hour which "should" equate to around 99 tips (~ 20mm) if all is as expected. Of most interest is simply the number of tips and for measuring this I use an old WMII console.

As for facts well I am really interested in how even 100ml can be evenly put through a Davis VP2 rain collector over 1 minute and create any form of swirling, it's not going to happen, try it.

Now the other more important thing with the VP2 rain collector is to check the exit orifice of the hole just above the buckets as until recent times the this was usually jagged, ragged and uneven from the moulding process. All cones should be checked for this as this definatley could cause deflection of water to one side on exiting the bottom of the cone. Fix is a small fine single cutting countersink and rolling in the fingers only lightly remove any burs.

In saying that most of the newer cones are not bad and especially a lot better than the older ones.        

 

But shouldn't it be accurate to pour a measured amount of water of a given millimeters to see how the readings correlate otherwise how would one know that they received 0.08 or 0.12 inches unless they knew the amount I saw somewhere someone took a pipette like those used in laboratories with a known amount of water and had it open enough to dribble the water and the rain gauges correlation to the amount that was sent through the rain gauge.

[Skywatch]

Of course you tip it to find out it has 0.01 increments

Simply tipping will not show what the increments are as one tip is simply one tip, the increment is related to the counter weight AND the software configuration AND rain calibration#.

 One tipe is simply one tip. True with Davis, but not true with all manufactures like Oregon scientific which uses 0.04 increments. I'm not shure what it's accuracy is, or counter weight. My geuss is it takes about 8/10th's of the tipping mechanism's max volume to tip it. Given the size of the buckets the diameter of the gauge funnel along with the weight on the balance are compensated by the varying increments.