Understanding Weather and Climate (7th Edition) (MasteringMeteorology Series) by Edward Aguado, James E. Burt.
► Hydrostatic Balance = if the net upwards force is equal to the downward force
─ For an atmosphere in hydrostatic balance, the balance of forces
in the vertical requires that…
► Or, the Hydrostatic
Equation:
─ The negative sign ensures that the pressure decreases with
increasing height
─ Because
we can rearrange the hydrostatic equation to
give…
► Above a fixed point on Earth…
─ That is, the pressure at height z is equal to the weight of
the air in the vertical column of unit cross-sectional are lying about that
level.
Hydrostatic
Equilibrium
► Pressure gradient force causes wind to flow from high to
low pressure
► Air pressure rapidly decreases with altitude
► Gravity pulls all mass, including the atmosphere, downward.
► Hydrostatic Equilibrium = vertical pressure gradient force and the force of
gravity are normally of nearly equal value and operate in opposite directions
─ When, gravitational force = vertical pressure gradient
force in magnitude à no vertical
acceleration occurs
─ When, gravitational force > vertical pressure gradient
force à downward motion
When, gravitational force < vertical pressure gradient force à
updrafts can develop that are associated with powerful thunderstorms
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