Atmosphere & Ocean Circulation

Week

GEOS 3410

🪑

Week Schedule

Tuesday

Wrap up atmospheric forcings
Troposphere circulation
Ocean circulation

Thursday

Ocean circulation, cont…
Climate connections

Outside of class

Reading and questions for Lab 5 on Thursday
Lab 2/3 due 11:59 pm on Thursday

Energy imbalance → meridional heat transfer

COMET / MetEd / UCAR, via Giannotti 2013

Energy imbalance → meridional heat transfer

PW (10¹⁵ W)/ degree latitude

Ocean Wiki

Physics Refresh

Temp. & Pressure

Move from P_high → P_low

Temp. & Density

(buoyancy)

Conservation of momentum $$ \circ \rightarrow $$ (inertia)

Don't need to note these unless you could use the reminder :)

Circulation on a sphere

Motion on a rotating reference frame

NASA Earth Observatory

Coriolis Force

An inertial force that acts on objects traveling in a rotating reference frame.

(conserves momentum)

Coriolis in action (2D)

Wikimedia

Coriolis on Earth (rotating W→E)

Hemisphere	Path veers…
Northern	Right
Southern	Left

Ocean Wiki, NSIDC

Hemispheric differences in storm systems

Northern Hemisphere
(counterclockwise)

Southern Hemisphere
(clockwise)

Cyclone = low-pressure system

Wikimedia

Finally, it all makes sense…
🌀🚽🌀

Interhemispheric toilet flushes are all controlled by bowl morphology. Why?

Circulation on a rotating sphere

Intertropical Convergence Zone (ITCZ)

Wikimedia / NASA Earth Observatory

Horse latitudes (±30°)

Dry upper troposphere falls and warms adiabatically

Deserts in orange

ASU / NASA

Polar cells & the polar front

All together now — Tropospheric circulation

You should be prepared to construct this from first principles…

Convection stops at the tropopause (usually)

Image: Hussein Kefel

Tropopause height decreases with latitude

Ocean circulation: surface

Wind – friction → ocean surface

↗ wind direction ↗

Gyres

Large-scale ocean surface transport

Balance of wind-driven surface transport, coriolis effect, and gravity.

CMMAP

Ekman transport

(Northern Hemisphere)

Wind-driven transport of surface water, friction between water layers, and Coriolis force.
Ekman layer: depth from surface to reversed flow (~100 m depth)
Net transport in Ekman layer is orthogonal (90°) to wind.

Ekman transport in the subtropics

Geostrophic Balance

pressure gradient = Coriolis force

Geostrophic flow is the horizontal movement of surface water arising from a balance between the pressure gradient force and Coriolis force

NASA

Sketch 5 subtropical gyres

Homework

Add two subpolar gyres in the Arctic and try to figure out the Southern Ocean
hint: focus on the southern Westerlies (the polar easterlies are more coastal)

Sea surface elevation

Are gyres symmetrical?

ESA

Gulf Stream

NOAA

The gulf stream carries 55 sverdrups (1 Sv = 10⁶ m³/s)

Currents & eddies

Surface current: pronounced limb of a gyre
Eddies: small-scale, chaotic, temporary turbulent circulation associated with currents. The ocean version of weather.