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I've read about Windshear Awareness and there is mention of a Predictive Windshear System (PWS) which I believe is a function of the radar system of the aircraft itself.

To complement the reactive windshear system and provide an early warning of potential windshear activity, some weather radars feature the capability to detect windshear areas ahead of the aircraft.

This equipment is referred to as a Predictive Windshear System (PWS).

Are there any gound-based systems that detect possible windshear situations that generate automated warnings directly to planes on approach? Or is the information only distributed verbally by controlers (e.g. LLWAS)?

Albeit exceedingly rare, are there any automated warning systems to pilots indicating other sudden dangers, for example large seismic motion? For example, the automated stopping of high-speed trains - sometimes before the sesimic wave even reaches a particular train - is being explored (in places where earthquakes and high speed trains are both frequent).

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    $\begingroup$ There is at least a case for Hong Kong. The detection system feeds automatically the ATIS and the D-ATIS. D-ATIS is a digital ATIS, the information are sent to the aircraft using ACARS. See HKO booklet. There are research ongoing, and data transfert is being extended, the near future will certainly be more automated. $\endgroup$ – mins Nov 1 '16 at 11:41
  • $\begingroup$ @mins thanks for that! It's a good place to start. $\endgroup$ – uhoh Nov 1 '16 at 12:14
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Windshear, yes. Seismic events, no.

Most major U.S. airports have a LLWAS -- Low-level Windshear Alert System, which is essentially an array of anemometers around the airport which detect wind speed and direction. The values from each station are processed by a computer that uses algorithms to detect a windshear or microburst event, and it notifies controllers in the tower. As a simple example, if the anemometers around the perimeter of the airport are all pointing toward the center of the airport, that's a strong indication that there is a microburst over the center of the airport, with air descending into the ground and then spreading out in all directions. Obviously, the algorithms can detect cases beyond just that.

And, many airports supplement that system with Doppler radar as well.

Regardless of how they're generated (LLWAS with anemometers, Doppler, pilot reports, visual observations of blowing dust, etc), the warnings are broadcast by the tower controllers, rather than by any automatic system. In the aircraft, aural warnings from the GPWS (reactive windshear -- noting changes in groundspeed and sink) and the EGPWS (predictive windshear -- returns from the aircraft weather radar) are automatic, but they don't block a radio frequency. Automated alerts over the tower frequency might block an even more important transmission, so it's left to the controller's judgement when to broadcast the alerts. (They're usually pretty prompt!)

No airport I'm aware of has a system similar to what the OP described for seismic events. I would assume that the risks to a high-speed train from an imminent earthquake -- i.e. the train may derail at high speed with catastrophic results -- are far greater than the risks to aircraft. I've never read anything about what happens when you're landing or taking off in an earthquake, but I'd doubt that anything other than the most severe would have much effect. And if the earth is shifting enough that you can't keep the aircraft on the runway, well, it's a really bad day for pretty much everybody in that state that day!

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  • $\begingroup$ OK this is a helpful answer. I hadn't thought about frequency-blocking but that makes sense. Also, considering that trains spend all of their at-speed time (hopefully) on the ground while moving aircraft almost always not on the ground, sounds like a low-priority item. $\endgroup$ – uhoh Nov 1 '16 at 15:09
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    $\begingroup$ About sismic events, one problem is that they can easily liquefy the soil. It's not a matter of strength, but of seismic wave frequency. This phenomena is used in vibro-sinking of steel profiles. See soil liquefaction. A magnitude 5 or 6 earthquake is sufficient and not uncommon. $\endgroup$ – mins Nov 1 '16 at 16:05
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    $\begingroup$ @mins When this happens, I think you've got much bigger trouble than one landing aircraft :-) $\endgroup$ – yo' Nov 1 '16 at 23:14
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At some U.S. airports, there is a system called TWIP (Terminal Weather Information for Pilots) where pilots can access weather information at the terminal via ACARS, including windshear or microburst alerts ongoing at the airport.

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    $\begingroup$ Welcome to aviation.stackexchange! You could improve your answer by adding a reference link. $\endgroup$ – DeltaLima Jan 13 at 8:07

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