Dynamics: Nov. 11

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# Dynamics: Nov. 11 - PowerPoint PPT Presentation

Dynamics: Nov. 11. Which are non-divergent, irrational ??. Circulation:. =. Circulations often conserved. Orthonormal to div, vort. Deformation:. Flow can be broken down into divergent, rotational, and deformation components. Flow over mountains. Both deformation And shear

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Presentation Transcript

Circulation:

=

Circulations often conserved.

Orthonormal to div, vort.

Deformation:

• Flow can be broken down into

divergent, rotational, and

deformation components

Flow over mountains

Both deformation

And shear

Strengthen frontal

zones

Effective gravity g, includes centrifugal force

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

NH

momentum

*1/

In Boundary Layer, frictional drag in evidence

Wind speed sub-geostrophic, drifts towards lower pressure

fV = |P|cos

the centripetal acceleration to eqn of motion

Sub-geostrophic

Super-geostrophic

The vertical shear in geostrophic wind

Is related to the horizontal temperature gradient

Thermal Wind:

Barotropic atm => grad T =0 =>geostrophic wind constant

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