dynamics: nov. 11. which are non-divergent, irrational ??
TRANSCRIPT
Dynamics: Nov. 11
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Which are non-divergent, irrational ??
Circulation:
Circulations often conserved.
=
Deformation:
Flow over mountains
Orthonormal to div, vort.
Flow can be broken down into divergent, rotational, anddeformation components
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Both deformationAnd shearStrengthen frontalzones
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Effective gravity g, includes centrifugal force
Motion introduces additional force : Coriolis
f=
Flow to right of motion =>CW in NH
2 examples:•land-sea breeze (Hsu, 1970, MWR)• mountain slope/valley circulation (Rocky Mountains/Plains)• katabatic flow ?
INERTIAL CIRCLES: less common in atmosphere (less inertia)
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Motion determined by balance between pressure gradientForce, Coriolis force, frictional force
Geostrophic wind = balanced pressure/coriolis flow
Fx,y =vertical gradient in horizonalmomentum
NH
*1/
Midlatitude horizontal velocities ~ 10 m/sDv/dt ~ 10-4 m s-2
Coriolis force ~fV~10-3 m s-2
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, addthe centripetal acceleration to eqn of motion
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Sub-geostrophic Super-geostrophic
Thermal Wind: The vertical shear in geostrophic windIs related to the horizontal temperature gradient
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Barotropic atm => grad T =0 =>geostrophic wind constant
Equivalent barotropic
Again…
Explains why westerlies strongestAt top of troposphere
Do these plotsmake sense ??
30-yr Mean meridional Profile Of temp. and zonalWind, from Australia toEastern Siberia, January
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Cold advection Warm advection