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Rainfall intensity/duration


A little over a year ago I started a thread on Weather-watch regarding a home made disdrometer.

Before you ask...
From Wikipedia, the free encyclopedia
A disdrometer is an instrument used to measure the drop size distribution and velocity of falling hydrometeors. Some disdrometers can distinguish between rain, graupel, and hail.

Disdrometer is probably more than I really want, since the term implies measuring drop size and velocity. What I really want is just a way to know when the rain starts (sooner than the first click of the tipping bucket) and maybe a qualitative indication of intensity.

If you read that thread, you'll see that, last year, I made an experimental plate transducer from a sheet of Lexan and a piezo element, and made a few wav file recording with it.

Then it pretty much stopped raining. That was about the time I found an app called Skypipe. It's made for amateur radio astronomy but can be used for just about any signal you can jack into the audio inputs. The site mentions seismography and weather in addition to radio astronomy.

Today, rain on the way, I remembered all of that, installed Skypipe, hooked up my plate transducer, and got it running before the rain started.

So far, I'd say the concept and implementation is pretty sound (pardon the expression). Even in the high wind (gusts to 45 MPH), there was no discernible falsing and the trace was flat. Ones it started raining, the trace matched the perceived intensity. Below is a screen grab of a unitless trace representing rainfall intensity. I've stretched the default stripchart wider and set the duration to one hour.

I don't thing Skypipe has enough features to be the killer app for this (intensity trigger, uploading, etc) but it's a cool proof of concept.

The radar shows we are in for some pretty intense rain here in the next few hours. It'll be interesting to watch this.

The time scale is the last 60 minutes, and the hours are not clock time, but started at zero from program start time. This ends at 9:15 PM PST, and you can see the rain bands go through and build in intensity.

Neat. What do the numbers of the left of the graph represent?


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