permaculture

[Toby Hemenway <hemenway@jeffnet.org>]

A bit of nomenclatural clarity:  The phenomenon that Mollison in the 
Designer's Manual calls an Ekman spiral, the spiraling of wind when it 
hits a barrier, is not an Ekman spiral. I have not been able to find a 
name for that effect.

 Ekman spirals refer very specifically to an effect of the Coriolis 
force on ocean currents. Wind and the earth's spin cause ocean currents 
to be displaced in a downward clockwise spiral (in the Northern 
Hemisphere; counter-clockwise down under). Refs at
http://www.gfdl.gov/~a1g/Ekman_spiral.html
http://www.public.iastate.edu/~aecl410/wavecurr/sld004.htm
or just Google "ekman spiral"

Nice patterns, Loren. Ripples, some shear from two moving air masses, 
and some kind of swirling wake that's on its way toward being a von 
Karman vortex street.

Toby
http://www.patternliteracy.com

On Friday, January 30, 2004, at 08:50 AM, Loren Davidson wrote:

> I just saw this fascinating picture on Space.com:
>
> http://www.space.com/imageoftheday/image_of_day_040130.html
>
> Happy Friday,
>
> Loren