Geophysical Fluid Dynamics

“… study of naturally occuring,

large-scale flows on earth and

elsewhere …”

Definition Large-Scale:

Time Scale of Motion > Rotational Period

Condensation cloud as an F/A-18 Hornet flies at or near the speed of sound. Photo by John Gay

L~10-m

Geophysical Fluid Dynamics on Jupiter

NASA

L

L~10,000-km U~100-m/s L/U~27-days

Jet-on-Earth: L/U ~ 10/300 s = 33-ms

Wave-on-Jupiter: L/U ~ 107/100 s = 27-days

Compare time scale to the rate of rotation ?

Earth: ~ 2 / (24 hrs)Jupiter: ~ 2 / (10 hrs)

Rossby Number Ro=(U/L)/ >>1 for Jet-on-Earth <<1 for Wave-on-Jupiter{

“Katrina” Aug.-2005

L~1000-km U~30 m/s L/U~9-hrs Ro~0.4

Sea Surface

Temperature

Gulf Stream

Eddies

1997

Arctic Sea Ice off Alaska

Summer 2001

from MODIS

Optical Remote Sensing

Mixing without rotation

Mixing with rotation

http://paoc.mit.edu/labweb/GFDlab.htm

The waves have a period of about 3 or 4 days and a wavelength of 2000 to 2500 km [1200 to 1500 mi], typically (Burpee 1974).

High Pressure

High Pressure

Atmospheric Jet Stream : http://squall.sfsu.edu/scripts/nhemjetstream_model.html

1 Jetstream passing north of the UK bringing settled, dry and warm weather2 Jetstream passing further south, causing weather that is unsettled and cool for the time of year

x

y

y

z

National Weather Service

Planetary “Rossby”Wave Dynamics