What type of temperature?

[J07]

When looking at charts that show isotherms (or adiabats/quasi-adiabats) at 850hPa, 500hPa and so on, to what kind of temperature are they referring?

1) Temperature

2) Virtual Temperature

3) Potential Temperature

4) Potential Wet Bulb Temperature

5) Equivalent Potential Temperature

???

I always see it referred to as simply "temperature", but I don't know if this is abuse of definitions or not.

Thanks

[Gibli]

The 850, 700, 500mb charts which show isotherms are showing the actual air temperture or forecast actual air temperature - as would be measured by a thermometer attached to a weather balloon (radiosonde).

But beware models calculate other 'temperatures' which are useful in forecasting.

Gibli

[BrickFielder]

Yes isobaric level Temperature which is the actual temperature.

[J07]

Thanks guys