Can we determine that hail is falling on our home Weather Stations?

[iisfaq]

Can we determine that hail is falling on our home Weather Stations?

Does anyone know if anyone has looked into this?

Is ther any algorithms available for hail?

Obviously it gets cold when it is hailing - but I have not really looked into the exact conditions as detected by my station when a hail storm is occurring.

I know that most commercial use radar for detecting hail but it would be nice to know for us at home!

Chris

[WeatherHost]

Can we determine that hail is falling on our home Weather Stations?

If the outdoor sensors get smashed to bits, you can assume there was hail.  B)

 Obviously it gets cold when it is hailing -

Not necessarily.  It only needs to be cold enough aloft.  You can have hail at the ground in 80 degree weather.


In the US, there are radar products available free to the public that indicate hail aloft.  Not sure about NZ.

[Weather Display]

using disdrometer you could
(Weather Display supports a home made one, interfaced to a sound card...the rain drops make sound...and that is plotted...hail might make a different signature)

[iisfaq]

using disdrometer you could
(Weather Display supports a home made one, interfaced to a sound card...the rain drops make sound...and that is plotted...hail might make a different signature)

Hi Brian

Do you know if it does make a different sound? I assume you have done some testing..

I will take a look and see what I can find - Down in CHCH we will probably get a bit of hail over the next few months - do you get any near Auckland?

Chris

[SLOweather]

It's easy to make. My prototype is a piezo transducer from Radio Shack, a cable with a mini phone plug on it, a pane of Lexan from Home Depot, and a 1" x 4" wood frame to mount the Lexan on.

Break the transducer out of its plastic shell and epoxy it to the center of the Lexan. I roughed up the Lexan first with some fine sandpaper. Assemble the frame, and stick the Lexan to it with some double sided foam tape. Connect the cable to the transducer and plug it in to the computer's mic jack.



My first experiments were recording the sounds of rain. Then I used Radio-Skypipe to plot the trace during storms.



you can clearly see the bands of rain come through, and the intensity build.

You could record rain and hail separately and see what the sonic differences are, maybe apply FFT to the output to determine rain or hail. Somewhere I have a couple of wav files I recorded. I'll see if I can fine them.
 

[SLOweather]

I found the rain wavs. Sorry, no hail wavs. We don't get much here.

WARNING! Each of these files is 10-12 megabytes. However, clicking on the links, at least in FireFox, opens a new tab and streams the audio, rather than downloading it.

Light rain

Moderate rain

Heavy rain

[Weather Display]

no testing here, I added the funcionality to WD for SLOWeather

[iisfaq]

Sounds interesting - I just bought a couple of Piezo Elements http://www.mindkits.co.nz/store/sensors/piezo-element

These are just the internals that Slo was talking about (I hope)

They probably won't turn up today/tomorrow so maybe a job for next week.

Looks interesting and a simple project as well.

Just about to download those WAV files and see what it sounds like - I may write my own software to capture the audio if I get a chance.

Chris

[iisfaq]

I roughed up the Lexan first with some fine sandpaper.

Does this step make a clearer/louder sound?

Chris

[iisfaq]

I found the rain wavs. Sorry, no hail wavs. We don't get much here.

WARNING! Each of these files is 10-12 megabytes. However, clicking on the links, at least in FireFox, opens a new tab and streams the audio, rather than downloading it.

Light rain

Moderate rain

Heavy rain

Have you changed the levels between these? The Light & Moderate rain sounds are louder than the heavy rain.

Chris

[SLOweather]

I roughed up the Lexan first with some fine sandpaper.

Does this step make a clearer/louder sound?

It makes the epoxy stick better to the Lexan.

[SLOweather]

Have you changed the levels between these? The Light & Moderate rain sounds are louder than the heavy rain.

Heck, I can't even remember how I recorded them. That was 4 years ago. And there are other variables that might affect the sound, like the size of the drops.

One thing I did notice and never really tested. The piezo element is fairly high impedance. I think the capacitance in the length of the cable connecting the element to the PC might affect the sound of the drops. It might act as a filter of sorts.

[Bushman]

A microphone would show  Hail having higher freqs than rain

[SLOweather]

Yeah, that's what I think I think. But, all rain sounds the same, regardless of drop size, due to the tympanic resonance of the Lexan. It just gets louder. Hail might have more high frequency components, but the same basic tone.

Hmmm. I suppose I could test it by hooking it up and dumping some plastic air soft BBs on it....

And, I couldn't remember the effect I was talking about re: the length of the cable. I figured it out. Cable length and capacitance may cause high frequency roll off of the audio.  

[Weather Display]

I know that the Vaisala WXt510 ultrasonic station has a rain detector that knows if its hailing and the size of the hail

[iisfaq]

It's easy to make. My prototype is a piezo transducer from Radio Shack, a cable with a mini phone plug on it, a pane of Lexan from Home Depot, and a 1" x 4" wood frame to mount the Lexan on.

In my part of the world Lexan is called Perspex.

Is there a particular reason you chose this? more sound recorded? Clearer sound recording?

I got my dev Piezo transducers a few days ago and cut a cable and got a sound recording on the PC Mic socket.

We have some plastic boxes in New Zealand called Sistema and I was wondering if one of those containers would be OK to use.

Ideal for your fridge, freezer and pantry, KLIP IT® food storage containers are microwave safe, dishwasher safe and incorporate a rubberised seal and easy access locking clips.

http://www.sistema.co.nz/pages/KLIP-IT/KLIP-IT.html

Your thoughts on this would be appreciated

Chris

[SLOweather]

Your thoughts on this would be appreciated.

OK, my main thought is that you are way overthinking what I did and why. This was at best a proof-of-concept experiment with materials at hand.

In my part of the world Lexan is called Perspex.

Is there a particular reason you chose this? more sound recorded? Clearer sound recording?

Because that's what Home Depot had in stock. I would have used acrylic or some other rigid plastic sheet instead of polycarbonate if that's what they'd had on hand. Lacking plastics, maybe I would have tried a sheet of aluminum.

Similarly, the dimensions of the device were dictated by the size of the pane I purchased.

We have some plastic boxes in New Zealand called Sistema and I was wondering if one of those containers would be OK to use.

Ideal for your fridge, freezer and pantry, KLIP IT® food storage containers are microwave safe, dishwasher safe and incorporate a rubberised seal and easy access locking clips.

http://www.sistema.co.nz/pages/KLIP-IT/KLIP-IT.html

Give it a try. There's no right or wrong way to build one of these, and this may yield better or at least different results. That's the fun part. Build one of each and try them side-by-side and see what the results are.

Here's one thing I have yet to try. You may have noticed that the tonal qualities of the rain sound similar no matter what the drop size or intensity is. Mainly, the amplitude of the audio changes. My assumption is that this is due to the resonance of the plastic plate.

I've wondered if using a piezoelectric film instead of the plate and element would yield different signals for different drop sizes. It might matter if the film were taut or loose, as well.

[SLOweather]

This is pretty interesting. Instructables has an article about building one of these. It's from July 2009, around a year after I first posted my project on the Internet for the first time.

Same basic construction, same form factor... Even includes an audio recording.

[SLOweather]

FWIW, here are other thoughts I've had regarding this type of sensor, but have yet to try.

Is a level sensor best? How does accumulated water affect the sound/intensity? Would a sloped surface be better as aiding drainage?

Is a flat sensor best? Would a dome or hemisphere be better? Smooth or geodesic?

What other sounds does the transducer pick up? I noticed wind on mine a couple of times. Should that be filtered out? How?

And, ultimately, what kind of data can be extracted from the acoustic stream and how? Applying audio filters? FFTs? There's probably some way to discern between rain and your hail, but I don't yet know what that is.

[iisfaq]

Thanks for all your feedback - I will do some experimenting and let you know

Chris