European METARs

[datafox]

Not sure if this is the apprporiate forum, but I have some questions about European METAR reports:

1) Why is CAVOK used? Canada, U.S. and Mexico do not use it. Why not just report the entire sky condition?

2) At large airports (BIKF, EGLL, EBBR, etc.) are observers there to back up automated equipment?

3) If there are observers, are they ATC personnel or meteorological personnel?

Thanks

[Gonzo]

At EGLL it's all done manually by a full time Met observer.

This will change shortly when we get a semi-automatic system which will be operated by some of our ATC staff.

[Chilli Monster]

1) Why not use it? The criteria are quite specific (Vis greater than 10km's, no cloud below 5000ft or MSA whichever is the higher, no precipitation, thunderstorm, CB clouds or any other Met phenomenon). For an aircraft landing at an airport if the Met conditions exceed that stated above then do you really need to know the vis is 30kms or the cloudbase is 20000ft? It's handy shorthand

2) Large airports have dedicated observers, who are employed by the relevant countries Meteorological services. They are the people who will produce the METAR - not an Automated system

3) See answer (2) above. At smaller regional airports (in the UK anyway) Met observations will be taken and METARs produced by ATC staff trained to do so. They wil submit these to a regional forecasting centre who will produce TAFs from the data supplied.

[datafox]

The reason I ask about observers is that here in the U.S.A., ASOS (Automated Surface Observing System) was put in place at most airports across the country. Initially, it was supposed to be a stand alone system, but since it screws up so much even ATC personnel don't have enough time to augment and replace data.

Here in the U.S., at least at the large airports there are still trained weather observers which back up the data. I hope Europe keeps full-time dedicated weather observers at all airports where automated systems exist.

The ATC people in the U.S. want nothing to do with ASOS.

[055166k]

Careful old chap, you seem to want to make order out of the total chaos that is modern global aviation. Now let's see, speed in Knots, height in feet, visibilty in metres but distances in miles when in the air but metric on the ground, altimeter setting in inches or hectopascals [sounds like a cough sweet], or millibars in the UK [ no problem...numerically same as cough sweets]. Fuel is hilarious...pounds or kilograms, US gallons or litres. In the UK we use a different kind of air in our atmosphere from that around the rest of our planet, this alters the laws of physics sufficiently to allow a unique set of wake vortex criteria......everybody else is wrong of course. Any long range aviator must go mad as he/she traverses the globe, each state's airspace could have its own unique set of peculiarities.....my sympathy to you all, and respect!

[Spitoon]

Unusually, CM is not quite correct. Many airports - typically the larger ones - in the UK now have semi-automated met observing systems. These are commonly called SAMOS (although not all SAMOS have the same functionality or capability). Most of these systems use automatic sensors to prepare a draft a METAR which is then completed by a human observer. To complete the METAR the observer will verify (or amend) the information that has been generated by the automatic system and will fill in the blanks where there are no automatic sensors. I think similar systems are in use in many places throughout Europe.

In many ways the current systems are little different to the traditional observervation made by a human. For example, it's a long time since an observer read a wet and dry bulb thermometer and used a slide rule to work out the dew point - there have been cheap sensors available for years where the observer simply reads the temperature and dew point and enters it in the METAR (which is then typed into a computer and distributed). The automatics simply collect all of the sensor data and start compiling the data on a computer.

In the UK, where there is an automated system it is usual for ATC to be responsible for producing observations - although at many of the smaller airports ATC staff have done obs for years. I don't know whether ATC people generally want to get involved with met obs or not - but it's the way things are going.

The thing that governs the way that aviation met is done in most parts of the world is ICAO Annex 3. This document is just being amended to provide for the use of automated observing systems. So, like it or not, I think you'll see more and more use of automation in met.

[Chilli Monster]

Unusually, CM is not quite correct. Many airports - typically the larger ones - in the UK now have semi-automated met observing systems. These are commonly called SAMOS (although not all SAMOS have the same functionality or capability).
True - we have SAMOS too. It is however the human that's the final arbiter of what is broadcast, not the machine (which is probably only true to the observed conditions 60-70% of the time, especially where cloud and vis are concerned - two of the most important factors in the METAR) which was the point I was making (albeit clumsily :uhoh: ).

[M609]

There is a BIG difefrence in performance on the automated systems. Som have better then 98% accuracy, ans some less then 60% as Chill said. I know from expericence that a AWOS delivered by AeroTech works well, IF you have all the sensors. (And the right ones!) I worked with it for several moths in Sweden, and it made very good METARS. It could even tell difference between ALL types of percipitation.
That said, by employer recently installed a system made bye Vaisala at Tromsø and Alta airports. And that system is really cr@p! It produces the most outlandish METARS at times!

But, I'm told you get what you pay for, and the Vaisala model cost a lot less then the Aerotech system. So the colleauges have gotten yet another pice of useless equipment.

I'm glad we still have a MET section, a least one good thing about working at an Air Base.

[datafox]

What does the Aerotech system have that the others do not?

In the U.S., our ASOS units usually only have one ceilometer and one visibility sensor. Therefore, any clouds not over the airport are not reported.

Our precipitation sensor only detects rain and snow, it can not detect other precipitation.

Our lightning system is not very accurate, and frequently report thunderstorms when they are 20-30 miles away from the airport.

What is the ICAO identifier of some AeroTech systems?

[M609]

The Arotech system I worked with had the following sensors:

2 Wind gauges (abeam each TDZ)
2 Ceilometers (approx on each outer marker)
3 Forward scatter meters, for visibility, percipitation and RVR (placed along the runway, allso detects if it is mist or haze)
3 pressure sensors
3 temprature gauges



During TWR hrs/opr the controller would check the metar before it was transmitted, and I think I had to correct it perhaps 3 times in 7 months. CAVOK has to be chosen by the controller (one click with the mouse)
During unattended hrs, the AWOS transmits in the auto mode, and "AUTO" apppears in front of the wind in the METAR.

ex of auto metar: ESTA 071620Z AUTO 12010KT 9999 NSC 26/12 Q1021=

Airports that I know have the Aerotech one: ESSA, ESTA, ESMT, ENTO, ESSP.
In Finland many Vaisala systems are running, and you can apparently get some high end systems from them as well.

The Vaisala system that my employer opted for is something like what you described datafox.