Transcript ppt

Geophysical Fluid Dynamics
“… study of naturally occuring,
large-scale flows on earth and
elsewhere …”
Definition Large-Scale:
Time Scale of Motion > Rotational Period
L~10-m
Condensation cloud as an F/A-18 Hornet flies at
or near the speed of sound. Photo by John Gay
Geophysical Fluid Dynamics on Jupiter
L
L~10,000-km
U~100-m/s
L/U~27-days
NASA
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 ?
 ~ 2 / (24 hrs)
 ~ 2 / (10 hrs)
Earth:
Jupiter:
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
High Pressure
High Pressure
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).
Atmospheric Jet Stream : http://squall.sfsu.edu/scripts/nhemjetstream_model.html
1 Jetstream passing north of the UK
bringing settled, dry and warm weather
2 Jetstream passing further south,
causing weather that is unsettled and
cool for the time of year
y
Planetary “Rossby”
Wave Dynamics
z
x
y
National Weather Service