When we were trying to fly kites we eventually noticed that the north (upwind) end of the field was doomed. Kites just wouldn't fly there. Several people even claimed that the wind was blowing down.

Rather than argue about it (well ok, after arguing about it) we decided to test it. After some discussion we collected some bubble wands and some soapy water and went back to the field.

The field we were using is at the top of a platoe on the ridge between the Gale's Creek wash and highway 8. Just to the north of the field is a line of trees and just beyond that there's a steep slope about 4 meters down to the track.

(South is to the left; North to the right. The wind was blowing North to South.)

When we blew bubbles on the south end of the field (off the left side of the diagram), they drifted upwards as they blew south.

When we blew bubbles on the north end of the field (just to the left (south) of the trees), they spiraled in crazy ways and often dove into the ground.

When we blew bubbles at the top of the rise (just north of the trees) they generally rose dramatically & often sailed over the trees. But some of them got caught near the ground and wandered at random until they popped.

When we blew bubbles at the base of the rise, they blew up along the slope and continued over the treed.

When we blew bubbles near the track. they sometimes rose and sometimes dove into the track. We thought the air over the track should be hotter and make them rise, but this didn't seem to happen.