[aprssig] Snow and Visibility on APRS
gerry.creager at tamu.edu
Thu Aug 19 19:39:35 CDT 2010
In my world, we do NOT have an "It's raining now" sensor. Nice idea, but
a lot of the "real" meteorological instrumentation is based on
techniques and procedures from long ago. The concept of hourly
measurements, and occasional higher frequency measurements, via SPECI
observations is how we get finer temporal granularity.
Newer instruments, however, can provide higher frequency measurements.
The problem is, at what rate do you sample these things? And, some
instruments, like Vaisala's "Weather Transmitter" (WXT-510/520) do
provide rate information.
Generally, in METARs, the instrumentation can provide when the first
bucket tip occurred, but it's back-stopped by the certified weather
observer (or tower controller) looking out the window.
Officially, a light, misting rain, with less than 0.01 inch accumulation
would be recorded as "trace" precipitation and wouldn't qualify as rain.
Max Harper wrote:
> Then maybe I need to come up with a "Raining Now" sensor. We can have a
> light misting rain
> that can go on for some time before the rain guage registers .01 or
> 1/100 of an inch. If you were
> outside during this you would be soaking wet LONG before the rain guage
> registered anything.
> On Wed, 18 Aug 2010, Max Harper wrote:
> >/ Something that has been on my wishlist for some time now is a "It's
> />/ Raining Now" flag. All the rainfall fields are after the fact, or how
> />/ much it HAS rained. I'd also like to see a "Rate of Rainfall"
> field. In
> />/ a heavy rain the console of my Davis Vantage Pro2 wil say "It's
> />/ Cats and Dogs" so I know the data is in there. Just need a field to
> />/ it in and a software update from Davis to output it to APRS. Thinking
> />/ about it more, if there was just a "Rate of Rainfall" field then
> />/ anything above 0 (zero) would mean it's raining now. Max KG4PID
> I suppose that would be duplicate data from the other counters, and would
> unnecessary grow the packets. The "raining now" status can be derived from
> two sequential packets - if the "amount of rain since X" counters are
> getting incremented, it is raining now. It's straightforward to improve
> the receiving software to do this calculation, and it'll work for all the
> existing weather stations which don't send such a preprocessed value.
> I guess i'll simply have to add "raining now" or "rate of rain" display in
> aprs.fi weather indications, it's simple to do and quite useful.
> Thanks for the inspiration!
> - Hessu
> aprssig mailing list
> aprssig at tapr.org
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University
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