# Pressure layer without height Slider?

• If i choose the pressure layer in ECMWF , then the height slider disappears. Bug or feature?

• @tomber42
I think is normal. Pressure is at sea level (m.s.l.).
If you change the height , let say at 1500m, then the pressure is the same (850 hPa) in the whole area.
When you change heights, actualy you see a constant pressure field.
At this field you can display geopotential height isolines.

• @meteo-gr OK,then I think I do not understand this with geopotential hight.. But that's OK, because I'm not a meteorologist 😁😁

• @meteo-gr
I have some problem to understand your explanation. Up to now, I learned that at 1500m the « average » pressure is 850hPa, and at sea level the « average » pressure is 1013hPa. But at these different levels the pressure varies.
At sea level, man uses to show the pressure measured at this level. But in altitude, the habit is to show the levels (more exactly the Geopotentiel Heights) at which a pressure is reached (e.g. 850hPa).
Am I right ?
It should be nice to have Geopotential Height layers at Windy, not only Geopotential Heights as isolines.

• @idefix37

1. Am I right ? ..... Yes you are!

2. Why? .... "Since most aircraft of the time used pressure altimeters, most "constant altitude" flights were actually flown on constant pressure surfaces.
Furthermore, the radiosonde data (from which the charts are prepared) are reported in terms of pressure.
Finally, use of pressure as the vertical coordinate simplifies many of the thermodynamic equations and computations."
source: http://www.meteor.wisc.edu/~hopkins/aos100/upairmap.htm

3. Geopotential Height layers in colour instead of isolines ? Yes, is a good idea ... BUT ... those charts are a specialized product for meteorologists and they preffer the traditional way with isolines!
A useful product will be the combination of GH isolines with the vorticity field in colour, but maybe we are moving away from Ivo's goal to goal "to keep Windy small and fast".

• @meteo-gr
Thank you for this complete overview.
I must admit that it’s better to keep Windy simple and fast.

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