Low velocity wind physics

tasp77

How slow can wind blow on earth (and elsewhere) before local obstructions (trees, hills, buildings) essentially stop it?

How low a wind velocity can be measured, and does the wind velocity spectrum extend to zero?

I was wondering about wind speeds in the 0 to 10 centimeter/second range. I was recently watching a small trash fire and I noticed the smoke plume was not quite vertical, but a nearby weather station anemometer was motionless. Are very low wind speeds (not stationary) important to weather predictions and climate models? (I'm thinking a very low velocity parcel of air would be more likely to saturate in humidity over a lake as opposed to wind moving over the lake at a higher speed).

Andre

Normally below a speed of 7 knots the direction tends to become 'variable'.