Dynamics:
Nov. 11
Which are non-divergent,
irrational ??
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Circulation:
=
Circulations often conserved.
Deformation:
Flow can be broken down into
divergent, rotational, and
deformation components
Flow over mountains
Orthonormal to div, vort.
Both deformation
And shear
Strengthen frontal
zones
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Effective gravity g, includes centrifugal force
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Motion introduces additional force : Coriolis
f=
Flow to right of motion =>CW in NH
INERTIAL CIRCLES: less common in atmosphere (less inertia)
2 examples:
•land-sea breeze (Hsu, 1970, MWR)
• mountain slope/valley circulation (Rocky Mountains/Plains)
• katabatic flow ?
Motion determined by balance between pressure gradient
Force, Coriolis force, frictional force
Midlatitude horizontal velocities ~ 10 m/s
Dv/dt ~ 10-4 m s-2
Coriolis force ~fV~10-3 m s-2
Geostrophic wind = balanced pressure/coriolis flow
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NH
Fx,y =vertical gradient in horizonal
momentum
*1/
In Boundary Layer, frictional drag in evidence
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Wind speed sub-geostrophic, drifts towards lower pressure
fV = |P|cos
Gradient Wind: in regions of high curvature, add
the centripetal acceleration to eqn of motion
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Sub-geostrophic
Super-geostrophic
Thermal Wind: The vertical shear in geostrophic wind
Is related to the horizontal temperature gradient
Barotropic atm => grad T =0 =>geostrophic wind constant
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Equivalent barotropic
Again…
Explains why westerlies strongest
At top of troposphere
Do these plots
make sense ??
30-yr Mean meridional
Profile Of temp. and zonal
Wind, from Australia to
Eastern Siberia, January
Cold advection
Warm advection
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