This imageis interesting only to the glider pilot. The stack is 35 meters tall;
the smoke rises straight at first because the lowest 120 meters of the atmosphere
is very cold, from heat radiating away into the night from the twigs of the trees.
Above this inversion, the air is warmer, so the smoke stops rising, and up there
the gradient wind blows freely, taking the smoke off to the southwest.
If the gradient wind was at about 10 kt, and the glider pilot skilled, it should be
possible to swoop into and out of the inversion layer, using the difference in
speed between the gradient wind and the still inversion layer to stay aloft: this
is called "dynamic soaring."
Sodankyla, Finland; Kininen River. March 13, 2002
Copyright 2002 Daniel L. Johnson

Nocturnal inversion:
This is a 35-meter smokestack in Sodankyla, Finland early in the morning after a
clear night. The water vapor rises straight up through the still air of the nocturnal
inversion; then is carried southward by the gradient wind aloft. If this stack is
100 feet tall, then the inversion layer is about 300 feet thick. If the gradient
wind is 10 kt or more, then a sailplane could use the local shear for dynamic
soaring. If the pilot felt comfortable close to the ground.
Photo March 14, 2002, Daniel L. Johnson mailto:drdan AT wwt.net
Created with The GIMP
Copyright © 2002 Daniel L. Johnson


Except as explicitly noted otherwise, all images Copyright © 2002 Daniel L. Johnson.
All rights reserved.