The still-air boundary layer near the ground is thick enough to trap kites

Evidence

At a larger scale, I encounter these layers of air every spring. On the first mild day in April, our beautiful kites that have been hanging draped with cobwebs on the porch all winter rustle in the breeze and remind us of blue sky. So, we take them out to play in the boundary layer. In our sheltered valley, the breezes are seldom strong enough to immediately catch the big dragon kites that the kids and I love. So we run crazily back and forth over the back pasture, dodging cow pies and trying to generate enough wind to carry the kite upward. Close to the surface of the earth, the winds are too slow to support the kites’ weight. They are trapped, beyond the reach of the breeze. Only when our mad dashes loft one of the kites up to escape the layer of still air does it pull and dance on the string. Its wild pitches and threatened crashes show that it has ascended into the turbulent zone. And then at last, the kite’s string pulls taut and the red and yellow dragon sails into the freely moving air above. Kites were made for the airy zone of laminar flow; mosses were made for the boundary layer. — Robin Wall Kimmerer, Gathering Moss, 97

Categorization

• XREF: A perfect example of Kimmerer’s method from Braiding Sweetgrass — intimate domestic/playful anecdote (kites with the kids) braided with fine physical reasoning; supports the polyad thread of observation-as-method at landscape scale, complementing the Soundscape work on boundary/ground layers. — connects to: Mosses stay small because they have no water-conducting vascular tissue — Robin Wall Kimmerer, Gathering Moss: A Natural and Cultural…, 89; Mosses move water passively by harnessing surface forces rather than expending energy — Robin Wall Kimmerer, Gathering Moss: A Natural and Cultural…, 200
• SEED: Could anchor an essay or lesson on tactile, body-scale demonstration of the boundary-layer concept as a modeling technique for teaching any invisible physical phenomenon.