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Simulate High Altitude Wind when Live Weather running

Postby tonghuix » Wed Nov 01, 2017 8:51 am

Hi,

I noticed that when live weather running, high altitude wind (aka wind aloft) is same as surface, such us when a METAR say 11003KT, it seems all altitude has the same wind direction and speed, I checked with IDG-A3XX and some other aircraft which could indicate outside wind, same result. I do believe it is vital for FDM of airliner aircraft because it influence the performance of a aircraft which fly higher. Due to Atmospheric circulation and less terrain influence, the high altitude wind is stronger and even total different from surface. I think if this feature implemented, some aircraft's FDM may have to redesign.

Here is a screenshot of Skyvector, it shows winds at FL180. Most wind at 20~60kt, some wind at 80~100kt, after adjust to higher altitude FL340, the wind stronger most wind blow at 80~100kt.

Image
Image

So, dose FG has some predefined Atmospheric circulation data or fetch live data from somewhere, and simulated?

After some research, I suppose FG could get Global Forecast System (GFS) data from NOAA, http://nomads.ncep.noaa.gov/, and a awesome project which could display global winds https://github.com/cambecc/earth
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Re: Simulate High Altitude Wind when Live Weather running

Postby BEL ISAAK » Wed Nov 01, 2017 4:03 pm

A basic implementation of aloft winds has been made. In the settings of detailed weather, choose 'aloft waypoints', you 'll get stronger winds with increasing altitude. Not based on reality, but more realistic than nothing.

I believe there once has been an effort to pull the real life winds, but I don't think it has been finished.
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Re: Simulate High Altitude Wind when Live Weather running

Postby Thorsten » Wed Nov 01, 2017 6:09 pm

I believe there once has been an effort to pull the real life winds, but I don't think it has been finished.


This used to work, but the site which provided it closed. The technology is all there in the weather systems, just someone needs to set up the data to be fetched and dumped into properties.
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Re: Simulate High Altitude Wind when Live Weather running

Postby Hooray » Wed Nov 01, 2017 7:20 pm

which should be a good reminder for all of us why adding more and more functionality to FlightGear with the implicit assumption of fgfs "always being online" and certain web-services always being available, is probably not a good idea without also providing a fallback for the offline use-case
Please don't send support requests by PM, instead post your questions on the forum so that all users can contribute and benefit
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Re: Simulate High Altitude Wind when Live Weather running

Postby Thorsten » Thu Nov 02, 2017 5:45 am

Oh, this actually works fine for the offline case - you can enter and run rather sophisticated windfields, or you can let the offline engine generate high altitude winds - it just doesn't work for the online case.
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Re: Simulate High Altitude Wind when Live Weather running

Postby tonghuix » Thu Nov 02, 2017 9:58 am

I just searched the wiki, and found http://wiki.flightgear.org/Howto:Fetch_live_aloft_data, so I tried set /environment/params/metar-updates-winds-aloft to false and set wind to 'aloft waypoints', it works fine now with live METAR, and wind aloft, as expect, appear!

However, the wind speed and direction may not accuracy, it may have to update the aloft date. Following shows how aloft at FL370. it should be tailwind 080 deg at 110kt in real.

Image

I wounder what we need is just a static aloft date winter version and summer version included. No need for fetching live date, but it is more realistic, and helping scientific research using FG.
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Re: Simulate High Altitude Wind when Live Weather running

Postby Thorsten » Thu Nov 02, 2017 10:51 am

I wounder what we need is just a static aloft date winter version and summer version included.


High altitude winds aren't static, they change a lot. The jetstram meanders in Rossby waves, which essentially is what drives the low-altitude weather systems.

Anyway - AW has the aloft waypoints mode for winds, so you can create any weather model you fancy and write a script to initialize AW with it, and it'll do what you ask it to.
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Re: Simulate High Altitude Wind when Live Weather running  

Postby V12 » Tue Nov 07, 2017 9:25 am

Nice wind visualisation is on https://www.windy.com, or https://earth.nullschool.net. Fetch live data should be better than use some predefined datasets. And when fly offline, possibility to use predefined alofts should be nice too.
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