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Meteorology
WCHS Meteorology Chapter 19
| word | definition |
|---|---|
| air pressure | is exerted in all directions; pressure pushing down on an object exactly balances the air pressure pushing up on the object |
| barometer | is a device used for measuring air pressure; when air pressure increases, the mercury in tube rises, when it decreases, the the mercury falls; invented by Torricelli in 1643 |
| Wind | is the result of horizontal differences in air pressure, air flow from areas of higher presure to areas of lower pressure |
| pressure differences | the unequal heating of earth's surface; solar rediation is the ultimate energy source for most wind |
| wind control | three factors combined; pressure differences, the Coriolis effect and friction |
| pressure gradient | the amount of pressure change occurring over a given distance; closely spaced isobars indicate a steep pressure graidient and high winds, widely space isobars indicate weak pressure and light winds |
| Coriolis effect | describes how earth's rotation affects moving objects; all reee-moving objects or fluids, including the widn are deflected to the right of their path of motion in the Norhtern Hemisphere, and to the left in the sourthern hempsphere |
| jet streams | fast-moving rivers of air that travel between 120 and 240 kilometers per hour in a west to east direction |
| cyclones | centers of low pressure; pressure decreases from outer isobars toward the center |
| anticyclone | Centers of high pressure; isoubars increase from the outside toward the center |
| friction | causes a net flow of air inward around a cyclone and a net flow of air outward around an anticyclone |
| pressure gradient & Coriolis effect | applied to pressure centers in the Northern Hemisphere, winds blow counterclockwise around a low, and clockwise around a high. |
| trade winds | two belts of winds that blow almost constantly from easterly directions; travels toward the equator; are located on the north and south sides of the subtropical highs |
| westerlies | travels toward the poles; the dominant west-to-east motion of the atmosphere that characterizes the regions on the poleward side of the subtropical highs |
| polar easterlies | winds that blow form the polar high towards the subpolar low |
| polar front | the stormy frontal zone separating cold air masses of polar origin from warm air masses of tropical origin |
| monsooms | seasonal reversal of wind direction associated with large continents, especially Asia; in winter, the wind blows from land to sea; in summer, the wind blows from sea to land |
| local winds | caused either by topogrpahic effects or by variations in surface compostiion, land and water, in the immediate area |
| prevailing wind | a wind that consistently blows from one direction more than from another |
| anemometer | measuring instrument commonly used to measure wind speed |
| El Nino | at irregular intervals of 3-7 years, warm countercurrents become unusually strong and replace normally cold offshore waters with warm equatorial waters |
| La Nina | opposite of El Nino, once thought to be normal conditions, now considered to be an important atmospheric phenomenon; when surface temperatures in eastern Pacific are colder thatn average |
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dmoudy
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