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Definition
| Air in motion measured relative to the Earth's rotating surface. |
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Definition
| A push or pull on an object computed as mass times acceleration. |
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Term
| Newton's Second Law of Motion |
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Definition
| A net force is required to cause a unit of mass of a substance to accelerate; force equals mass times acceleration. |
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Definition
| Change in air pressure with distance. |
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Definition
| A force operating in the atmosphere that accelerates air particles away from regions of high air pressure directly across isobars toward regions of low air pressure in response to an air pressure gradient. |
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Definition
| An inward-directed force that acts on an object moving in a curved path, confining the object to the curved path; the result of other forces. |
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Definition
| An apparent deflective force arising from the rotation of the Earth on its axis; affects principally synoptic-scale & planetary-scale winds. Winds are deflected to the right of their initial direction in the Northern Hemisphere & to the left in the Southern Hemisphere. Magnitude depends on latitude & speed of the moving object. |
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Definition
| The resistance an object encounters as it comes into contact with other objects; the friction of fluid flow is known as viscosity. |
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Definition
| Friction within fluids such as air & water. |
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Definition
| Fluid friction (viscosity) arising from the random motions & interactions of molecules composing a fluid such as air or water. |
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Definition
| Fluid friction (viscosity) arising from eddies (irregular whirls) within a fluid such as air or water. |
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Term
| Atmospheric Boundary Layer |
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Definition
| The atmospheric zone to which frictional resistance (eddy viscosity) is essentially confine; on average the zone extends from Earth's surface to an altitude of about 1000m (3300 ft.). |
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Definition
| A state of fluid flow characterized by irregular (eddy) motion. |
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Definition
| The force that accelerates air downward to the Earth's surface. It is the net result of gravitation, the force of attraction between Earth & all other objects, & the centripetal force arising from the Earth's rotation on its axis. |
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Definition
| Balance between the atmosphere's vertical pressure gradient force & the equal, but oppositely directed force of gravity. |
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Definition
| A hypothetical, unaccelerated horizontal wind that flows along a straight path parallel to isobars or height contours above the atmospheric boundary layer; results from a balance between the horizontal pressure gradient force & the Coriolis effect. |
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Term
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Definition
| A hypothetical horizontal wind that blows parallel to curved isobars or height contours, above the atmospheric boundary layer. The gradient wind differs from the geostrophic wind in that the path of the gradient wind is curved. |
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Definition
| A dome of air that exerts relatively high surface air pressure compared with surrounding air; same as a High. Viewed from above, surfaces winds in an anticyclone blow clockwise & outward in the Northern Hemisphere but counterclockwise & outward in the Southern Hemisphere. |
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Term
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Definition
| A weather system characterized by relatively low surface air pressure compared with the surrounding air; same as a Low. Viewed from above, surface winds blow counterclockwise & inward in the Northern Hemisphere but clockwise & inward in the Southern Hemisphere. |
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Definition
| An instrument used to monitor wind direction that consists of a free-swinging shaft with a vertical plate at one end & a counterweight (arrowhead) at the other end. The counterweight always points into the wind. |
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Definition
| An instrument used to monitor wind direction that consists of a cone-shaped cloth bag opened at both ends. The larger end is held open by a metal ring attached to a pole; air enters the larger opening, rotating the sock & stretching it downwind. |
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Definition
| A scale of wind speed based originally on visual assessment of the effects of wind on seas & later extended to describe the effects of wind on land-based flexible objects such as trees. The scale ranges from 0 for calm conditions to 12 for hurricane-strength winds. |
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Definition
| An instrument used to monitor wind speed. Wind rotates the 3 or 4 open hemispheric cups, which spin horizontally on a vertical shaft, & that motion is calibrated in wind speed. |
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Definition
| An instrument that measures wind speed based on the rate of heat loss to air flowing past a heated wire. The rate of heat loss from the wire to the air increases as wind speed increases. |
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Definition
| A wind sensor designed to measure wind speed & direction. |
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Definition
| An instrument sensor that emits sound waves to determine wind speed. |
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Definition
| Weather phenomena operating at the largest spatial scale of atmospheric circulation; includes the global wind belts & semipermanent pressure systems. These systems have dimensions of 10,000 to 40,000 km (6,000 to 24,000 mi) & exhibit patterns that persist from weeks to months. |
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Term
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Definition
| Weather phenomena operating at the continental or oceanic spatial scale; includes migrating cyclones & anticyclones, hurricanes, air masses & fronts. These systems have dimensions of 100 to 10,000 km (60 to 6,000 mi) & last from days to a week or so. |
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Definition
| Weather phenomena that may influence the weather in only a portion of a large city or county; includes thunderstorms, sea breezes, & lake breezes. These systems have dimensions of 1 to 100 km (1 to 60 mi) & last from hours to a day or so. |
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Definition
| Weather phenomena that represent the smallest spatial subdivision of atmospheric circulation, such as a weak tornado. These systems have dimensions of 1 m to 1 km (3 ft to 1 mi) & last from seconds to an hour or so. |
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