By Staff
Wind is born from changes in temperature. On a global level the sun is closest to the earth at the equator so this is the warmest area. Warm air is lighter than cold air so the warm equatorial air continually rises leaving a void. The cooler air at both poles is drawn into this void, creating wind as it moves along the earth's surface. The rising warm air is drawn over the cool air toward the poles to fill the void left by the cold air headed to the equator. As the warm air nears the icy poles it cools and sinks, squishing the air below out and further enhancing the never ending cycle.
At this point we would expect a constant wind blowing from the poles to the equator but many other factors enter into wind movement. The spinning of the earth interrupts this movement and causes the wind to swirl. Just like water running down a drain, in the northern hemisphere the wind is spun counterclockwise, the opposite in the southern hemisphere. But that's just the beginning of Mariah's whimsical demeanor.
Local temperatures vary greatly. When a given area warms up the air rises, creating a low pressure area. The adjacent cooler air -- remember cool air is heavier than warm air -- is a high pressure system. In an attempt to stabilize pressures the heavy cool air moves into the void of the low pressure area. Extreme temperature and pressure variations can cause extreme winds, tornadoes and hurricanes. Of course, other factors such as terrain also enter into the equation. Mountains, valleys, prairies, lakes, oceans and even big cities can block or enhance wind movement as well as create temperature changes that effect wind.
On a day to day basis the windiest place on earth is Antarctica. Here 100 m.p.h. winds are not uncommon with gusts up to 200 m.p.h. on record. The North Pole is also quite breezy and comes in second. The highest wind ever recorded was 231 m.p.h. Surprisingly, this wasnt at the South Pole but atop Mt. Washington in New Hampshire back in 1934.
As all of us know, wind plays a major role in our comfort outdoors. A sweltering 95 degree August afternoon can be rendered quite pleasant by a cool, dry breeze. On the other hand, an otherwise tolerable crisp morning on the deer stand can be turned into a penance in Hades by a stiff, cold wind. A breeze that makes small trees sway, meaning roughly 20 m.p.h., makes a 30 degree day feel like it's zero. We've all felt that dreaded wind chill. By the way, wind chill is a matter of heat being sapped from our bodies so it only affects living things. Inanimate objects remain the same temperature as the surrounding air regardless of wind.
By noting the surroundings you can determine wind speed quite accurately. At 1-3 m.p.h. smoke drifts. A 4-7 m.p.h. wind can be felt on your face. If leaves and twigs move the breeze is 8-12 m.p.h. and if small branches are moving its around 13-18 m.p.h. At 19-24 m.p.h. bushes and small trees are swaying. When the wind whistles through the wires and branches it's blowing 25-31 m.p.h. and if the big trees are swaying its kicked up to 32-38 m.p.h. At 39- 46 m.p.h. twigs are breaking off and it's difficult to walk. When bigger limbs start breaking the wind is around 50 m.p.h. and it's time to quit gawking at the trees and head for cover. Carpe diem.
Larry Lyons writes a weekly outdoor column for Leader Publications. He can be reached at larrylyons@beanstalk.net