Meteorology - Pressure

Indicated altitude

Is the altitude value currently shown on your altimeter without fixing any temperature corrections

True altitude

Where you plane is at physically, it’s indicated altitude corrected for any temperature error

Barometric altimeter

Is the altitude of an aircraft as measured by a barometer which determines altitude by measuring air pressure

Low pressure systems

Acts as a vaccum, causing the air to rise and as it rises the surrounding pressure reduces, causing the rising air to expand, cool and condense, producing clouds

Low pressure systems on charts

Are shown on weather charts by being closer together

How does wind behave below 3000ft in a low pressure system?

below 3000ft friction is in force, slowing the wind down enough that it loses its balance with the coriolis force and the vaccum effect wins, dragging the air up

How does wind behave above 3000ft in a low pressure system?

Friction dissapears, so the wind isn’t slowed down but speeds up. It is now balanced with the coriolis force and doesn’t get vaccumed but blows parallel to the isobars, spinning in a circle around the low

High pressure system

Dense, cold air sinks towards the Earth’s surface

Trough

An elongated region of relatively low atmospheric pressure. They are the dip. A trough forces air to crash together at the surface, which pumps the air upward to create storms.

QNE

The indicated height on landing when 1013.25 hPa is set; it is a height (not a pressure setting) used at high-elevation airfields when QFE/QNH cannot be set