The portion of the atmosphere which is above the lower troposphere. It is generally applied to the levels above 850 millibars. Therefore, upper level lows and highs, troughs, winds, observations, and charts all apply to atmospheric phenomena above the surface.
UPPER AIR/UPPER LEVEL
Meaning of UPPER AIR/UPPER LEVEL in English
Weather and meteorology English vocabulary. Английский словарь погоды и метеорологии . 2012