Todays lecture objectives:

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ATMS 305 Atmospheric Thermodynamics and Statics

• Todays lecture objectives
• The Hydrostatic Equation (WH 3.2)
• Understand the environment surrounding Polly
  Parcel in order to forecast if she will rise or
  sink in a given environment

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ATMS 305 The Hydrostatic Equation

• Todays lecture topics
• The Hydrostatic Equation (WH 3.2)
• Geopotential
• Scale height and the hypsometric equation
• Thickness and heights of constant pressure
  surfaces
• Barotropic atmosphere
• Reduction of pressure to sea level

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ATMS 305 The Hydrostatic Equation
0
0
0

• For large-scale atmospheric motions, Newtons 2nd
  Law for motion in the vertical reduces to

The hydrostatic equation
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ATMS 305 The Hydrostatic Equation
The hydrostatic equation
Fup Fdown
The upward force acting on a thin slab of air,
due to the decrease in pressure with height
(Fup), is generally very closely in balance with
the downward force due to gravitational
attraction (Fdown).
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ATMS 305 The Hydrostatic Equation

• At smaller scales in the atmosphere, there
  generally is not such a balance of forces in the
  vertical. As a result, one can get significant
  upward or downward accelerations of air parcels.

?
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ATMS 305 The Hydrostatic Equation
p2
Z
Layer 1
p1
Z
p2
Layer 2
p1
Which intervening layer has the warmest mean
virtual temperature?
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ATMS 305 The Hydrostatic Equation
(a) hurricane and (b) cold core upper low
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Barotropic Atmosphere
ATMS 305 The Hydrostatic Equation

• A simple situation where isobaric surfaces have
  constant temperature

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Example- Barotropic Atmos.
Z
ground
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