Surface pressure (QFE)
Air pressure station pressure surface air pressure
Surface pressure is air pressure at the actual location and elevation. In aviation, QFE refers to pressure at a specified airfield reference level.
The weight of the air above us
Air has weight, which produces pressure measured in hectopascals (hPa). Climb a hill and there is less air above you, so pressure decreases. Near the surface, roughly eight metres of height corresponds to one hectopascal, although temperature and weather alter this relationship.
Surface pressure versus sea-level pressure
Surface pressure refers to the actual measuring height. Sea-level pressure has been adjusted for elevation. Two nearby stations can therefore report different surface pressures without a particularly deep low sitting between them.
Where QFE fits in
QFE is an aviation altimeter setting referring to a specified airfield level. With this setting, a pressure altimeter reads approximately zero at that level.
A surface-pressure forecast is not automatically an official QFE. A weather model also has its own smoothed terrain height. If that differs from the real location, the pressure may differ too.
Which value should you use?
Surface pressure is useful for calculations at a particular location. To compare highs and lows on a weather map, use pressure adjusted to sea level.