Vincent D. Cashman, age 11, of San Francisco, California, for his question:
What causes air pockets?
The behavior of the air is mysterious because the whole thing is invisible. We cannot see even the wind only what it does to objects in its path. We cannot see tricky air pockets in the atmosphere, which is one reason why they are so dangerous to planes. When all of their causes are known, it is hoped that pilots can be warned when and where to expect them.
An air pocket is an unexpected patch of light air or perhaps turbulent air in the atmosphere. The gaseous air, of course, is more turbulent than the watery ocean and both are more restless than the solid earth. This is because gases and liquids are fluid, always eager to blow and flow. The filmy air is disrupted by heat and cold, by the earth's rotation, by the seasons and by the geography of the earth's surface.
These factors create enough turbulence to keep the air in a state of upheaval up to several miles above the ground. Nowadays, air traffic creates extra atmospheric turbulence.
A plane is designed to stay aloft on streaming cushions of air. When it flies into an unexpected patch of extra light air, this support suddenly is reduced. The situation is even worse when the half empty pocket happens to be a whirling draft of light air. Sometimes the pilot loses control and the plane plummets down to disaster.
Air pockets are often caused by geography. The air absorbs warmth from the land and sea below it. And certain areas of the surface absorb more of the sun's heat than others. The air above an extra warm surface patch becomes lighter and rises aloft in an invisible updraft. At present, there is no way for a pilot to detect such a tricky pocket in his path.
Other natural air pockets may be caused by weather conditions. Because the earth rotates, storm winds tend to veer around in circles. Sometimes a system of conflicting winds swirls around pockets of light, rising air. On a dramatic scale, this sort of thing causes tornados. The grand daddy of all air pockets is the vast eye of light, rising air at the center of a howling hurricane.
A thunderstorm is a medium sized mass of turbulent air. It too creates air pockets, sometimes bad enough to cripple a small plane. Turbulent tantrums also occur, with air pockets, when winds slide down a mountain slope and when masses of warm and cool air collide to form a weathery cold front.
Nowadays, paths of turbulence are created as giant jets fly through the sky. We now know that many hazardous air pockets form in the wake of large planes.
No plane can survive the turbulence of a hurricane or a tornado. But these airy booby traps give plenty of warning. Pilots also may be warned of possible air pockets in the wake of giant jets. At present, the sneakiest air pockets are the invisible, unexpected ones that form from updrafts above extra warm patches on the earth.