Global wind models

[Wishbone]

Other than for remote sensing and Cumulonimbus avoidance, clouds serve no useful purpose for spacefarers. Unless someone plans to dogfight in the atmosphere, this feature is IMHO not worth the expenditure of time to code and debug. You could add optical depth as another moddable and pluggable callback function, though:

double clbkOpticalDepth(const OBJHANDLE hBody, 
                                 const double Lon, 
                                 const double Lat,
                                 const double MJD) const;

 

[RisingFury]

Finally! This is gonna make reentries awesome again!

I do have a question... how will this work with existing addons? Mainly I want to know what happens to functions that return airspeed. Will you change them to include wind speed as well? Will you add a GetAirspeedEx with a parameter to include wind or to exclude it?

 

[Spacethingy]

Oooooooooo! Wind! Excellent. Thanks Martin! That'll add a nice extra level of detail, having to deal with weather! :thumbup:

Finally, the wind sound in OrbiterSound will actually mean something...

Edit: and this :tumbleweed: will have use too...

 

[Moach]

with weather and procedural terrain, Orbiter could very well take on M$FS one of these days... and it would win, dead sure

we need more runways :lol:

 

[martins]

Finally! This is gonna make reentries awesome again!

I do have a question... how will this work with existing addons? Mainly I want to know what happens to functions that return airspeed. Will you change them to include wind speed as well? Will you add a GetAirspeedEx with a parameter to include wind or to exclude it?

No, the GetAirspeed function will automatically include wind speed. Instead there will be a new function GetGroundspeed which will exclude the wind speed. This seems a more consistent convention than having a function called GetAirspeed to return ground speed, and GetAirspeedEx to return the actual airspeed. I don't see that as a problem with backward compatibility. Until now, GetAirspeed returned the correct airspeed value, because wind speeds were zero. I am simply extending this by introducing nonzero wind speeds.

The only problem is that addons that actually meant "ground speed" when calling GetWindspeed will have to be modified. But this doesn't seem to be worse than forcing modifications to the addons which really meant "airspeed".

 

[jangofett287]

Naturally there will be a launchpad tick-box to enable/disable the wind I assume? This would sort out backwards compatibility and low end computers.

 

[Ripley]

...What do other flight simulators use?

X-Plane downloads real METAR data.
http://code.google.com/p/fjccuniversalfmc/source/browse/wiki/Winds.wiki?spec=svn245&r=245

 

[ky]

We might as well add weather like rain or thunderstorms into this.If we do we could easily take on MSFS or MF(microsoft flight)as it's called now.Also take a look at this:http://cboard.cprogramming.com/cplusplus-programming/76998-flight-simulator-wind-speed.htmlI hope its of some help.

 

[martins]

Also take a look at this:http://cboard.cprogramming.com/cplusplus-programming/76998-flight-simulator-wind-speed.htmlI hope its of some help.

Wind speed perturbations drawn from a uniform distribution with hard edges, and an arbitrary correlation length of 10 seconds, determined by the sample density? I sincerely hope that this is not how flight simulator models its wind speed! If the guys in that thread had at least used a normal distribution, it wouldn't look so bad ...

No, I think for orbiter we should be able to come up with something a bit more sophisticated.

 

[Ripley]

...What do other flight simulators use?

FlightGear also uses METAR plus Jeppesen data

http://wiki.flightgear.org/Howto:_Fetch_live_aloft_data
http://www.jeppesen.com/aviation/personal/aviation-weather.jsp


Condor: The Competition Soaring Simulator features (but this is maybe beyond our scope)
Realistic thermals life cycle: starting from the ground they reach cloud base, the cloud becomes bigger and more dense and later dissipates which causes the air below it to sink.
The location and strength of thermals is based on terrain sun exposure and ground features like forests, fields and villages.
Realistic daily sun travel which affects the frequency and strength of thermals.
Up slope wind on sunny ridges (anabatic winds).
Ridge lift with leeward downwind and turbulence, venturi effects.
Waves behind ridges, wavelength depends on wind speed and stability of the atmosphere.
Correct atmosphere pressure, density and temperature height distribution.
3D isotropic turbulence model for thermal and mechanical turbulence.
preset and custom weather conditions.

 

[Grover]

with all this Atmosphere work going on, would it be a good time to suggest a few "upgrades" to Orbiter's Atmosphere system (for Earth at least)

as well as wind (and natural Jetstreams are very relevant as well) why not improve the cloud system. i dont mean to go all the way as NEBO clouds (very resource consuming, it would outdate some systems that we Orbinauts use) but rather a simpler alternative, like 2d clouds drawn at distances >3Km, similar to the contrails drawn by exhausts) and rendering some [slightly] more complex clouds closer to the vessel.

then using a system similar to retrieving wind speed/direction, it wouldnt be too hard to make some parts of the world realistically clear/cloudy

i'm sure that other people could come up with other ideas as well, or possibly make mine far more efficient code and graphics wise, but its just a suggestion

Thanks!

 

[ky]

Right now downloading Fighter Ace 10 a combat flight simulator.I'll see what it uses to produce winds.

 

[Urwumpe]

I would say surface winds aren't enough, we need the full troposphere range.

Also, many rocket launches are stronger influenced by current local weather than global or average winds. High fidelity means high CPU load in general, but maybe it is possible to optimize the wind models around the bases and have less accurate winds far away?

 

[Wishbone]

In such case would ask for a superposition of wind models - letting the player select not one but several wind modules, in some order. If a higher-priority wind module returns a vector with at least one element being NaN or infinity, the engine would poll the module which is standing next in the queue. In this way, you can have KSC weather and global weather at the same time (while hoping that the transition gust will not fool the autopilot into a nosedive).

 

[ky]

It seems that Fighter Ace uses a DLL for winds and weather in general.BTW fighter ace is very addictive but it couldnt take me away from orbiter.

 

[markp]

Hi, the Weather Research and Forecasting model might be a useful resource with regard to obtaining some wind velocity vectors?

http://www.mmm.ucar.edu/wrf/users/
http://planetwrf.com/home/

 

[Wishbone]

The question is, will people be ready to run WRF at home? It is easier to download a hemispheric GRIB file than to set up the model. Check out http://www.zygrib.org/ (it downloads GFS run results from NOAA)

 

[JohnGill]

I am currently experimenting with wind - the stuff that tends to blow aircraft off course and turns landings into hit and miss affairs. I don't want to implement this as just random vector fields, but give it at least a semblance of a plausible global field distribution. Therefore, I am looking for reasonable (and reasonably simple) global wind models. For example, mean vector field distributions as a function of

• latitude
• altitude
• season

For a refinement, possibly also

• longitude
• time of day

In addition to the means, possibly also standard deviations on different time scales and "typical" variations (distribution and temporal development of high/low pressure regions and resulting wind patterns).

Does anybody have a suggestion? I came across this paper, which has some useful information to start with. Although digitising the plots would be a pain. Vector field data in electronic format would help a lot. Also the graphs are slightly puzzling me. The vector fields appear to have a strong east/west orientation, with hardly any north-south component. I though the convection towards the equator at low altitudes (and flow away from the equator at high altitudes) was a major component of the global wind pattern. Is the magnitude of solar panel effect so much smaller than the east-west component?

Apart from the global average effects, some models of small scale effects will also be needed. (turbulence, gusts, etc.) What are the (spatial and temporal) correlation lengths, i.e. how rapidly can the vectors change over time and space?

Are there any public-domain global wind algorithms around? What do other flight simulators use?

Hello friend sorry for old thread reply but were you able to design an effective and efficient wind model? I am searching for good wind model can you help me out? Waiting for reply thanks in advance