Weather. Dynamics in Earth’s Atmosphere. What Drives Air Motion?. Warm air rises and cools as it expands. Cool air falls to fill the space left by warm air. This sets up a vertical convection current . Particles exert a force as they move and this force per unit area is called pressure.
Dynamics in Earth’s Atmosphere
The columns in the first set have the same
temperature and pressure at each altitude. The
second set shows a cold and warm column. You have
to go higher in the warm column to get the same
pressure as in the cold. Therefore, the pressure is
higher at the same height in the warmer air column
compared to the cold.
Particles move from areas of high pressure to areas
of lower pressure because of a pressure gradient.
The moving particles exert a pressure-gradient
force. In the case of cold and warm air columns, air
will move from the warm to the cold column at the
same height. This movement generates wind.
This is a contour
display of pressures
at the surface.
high pressure system
Air circulation around a low
is lower pressure, red is higher)
Plot of wind direction-
Note that the winds are
around the low and clockwise
around the high region.
influence on the movement of weather systems
across the globe.
as viewed from
the South Pole