The Atmosphere:Part 5: Large-scale motions

• Composition / Structure

• Radiative transfer

• Vertical and latitudinal heat transport• Atmospheric circulation• Climate modeling

Suggested further reading:

Holton, An Introduction to Dynamical Meteorology (Academic Press, 1979)

Calculated rad-con equilibrium T vs. observed T

pole-to-equator temperature contrast too big in equilibrium state (especially in winter)

Zonally averaged net radiation

Diurnally-averaged radiation

Implied energy transport: requires fluid motions to effect the implied heat transport

Observed radiative budget

Roles of atmosphere and ocean

Trenberth & Caron (2001)

net

ocean

atmosphere

Basic dynamical relationships

dudt

2 u p friction

Ω

φ

u

ΩΩsinφ

dudt

fv 1

px

dvdt

fu 1

py

f 2 sin

Equation of motion

Shallow atmosphere:

p z x,y

g

1

px z

g zx p

1

py z

g zy p

} z - coordinates

dudt

fv g zx

dvdt

fu g zy

} p - coordinates

Basic dynamical relationships

dudt

2 u p friction

Ω

φ

u

ΩΩsinφ

dudt

fv 1

px

dvdt

fu 1

py

f 2 sin

Equation of motion

Shallow atmosphere:

p z x,y

g

1

px z

g zx p

1

py z

g zy p

} z - coordinates

p

x zx

p

z x z

0 p px z

x p z x

z

zx p

zx

px z

/p z x

1g

px z

Basic dynamical relationships

dudt

2 u p friction

Ω

φ

u

ΩΩsinφ

dudt

fv 1

px

dvdt

fu 1

py

f 2 sin

Equation of motion

Shallow atmosphere:

p z x,y

g

1

px z

g zx p

1

py z

g zy p

} z - coordinates

dudt

fv g zx

dvdt

fu g zy

} p - coordinates

fu g zy

fv g zx

Geostrophic balance

dudt

fv g zx

dvdt

fu g zy

Ro UfL

1

fu g zy

fv g zx

Geostrophic balance

dudt

fv g zx

dvdt

fu g zy

p z x,y

g

zp x,y

1g R

gp T

2zpx

Rgp

Tx

up

Rfp

Ty

vp

Rfp

Tx

thermal wind shear balance

Ro UfL

1

Rotating vs. nonrotating fluids

Rotating vs. nonrotating fluids

Rotating vs. nonrotating fluids

Ω

φ

u

ΩΩsinφ

f = 0

f > 0

f < 0

Atmospheric energetics:where does the energy of atmospheric motions come from?

Flattening density/temperature surfaces always reduces potential energy

Atmospheric energetics:where does the energy of atmospheric motions come from?

Flattening density/temperature surfaces always reduces potential energy

Available potential energy inherent in density/temperature gradients

Atmospheric energetics:where does the energy of atmospheric motions come from?

Flattening density/temperature surfaces always reduces potential energy

Available potential energy inherent in density/temperature gradients

In order to generate available potential energy, on average must heat where hot and cool where cold:

< JT > > 0

Atmospheric energetics:where does the energy of atmospheric motions come from?

Flattening density/temperature surfaces always reduces potential energy

Available potential energy inherent in density/temperature gradients

In order to generate available potential energy, on average must heat where hot and cool where cold:

< JT > > 0

In order to release available potential energy (and generate motion), on average, warm air must rise, cold air sink:

< wT > > 0