MET1010 Final Exam Review Geostrophic Wind Wind that flows in a straight path parallel to the isobars at a constant speed Results when the Coriolis force exactly balances the horizontal pressure gradient force Blows in the Northern Hemisphere with lower pressure to its left and higher pressure to its right if wind is to your back low pressure is to the left Gradient Wind Wind that blows at a constant speed parallel to curved isobars above the level of frictional influence Always blows from high to low pressure Force depends on the degree of curvature Centripetal Force Any force that causes an object to move in a circular path always acts to ward the center Southern Hemisphere is opposite the Northern Reason why hurricanes don t cross the equator Coriolis Force Happens because the earth is rotating all free objects ocean currents aircraft air molecules etc seem to deflect from a straight line path because the earth rotates under them Causes the wind to deflect to the right of its intended path in the Northern Hemisphere and to the left of its intended path in the Southern Hemisphere Magnitude varies with the speed of the moving object and the latitude as wind speed increases the Coriolis Force increases Acts at right angles to the wind only influencing wind direction and never wind speed Pressure Gradient Force Causes the wind to blow When differenced in horizontal air pressure exist there is a net force acting on the air Wind flows from high pressure to low pressure at right angles to the isobars Greater difference in pressure the stronger the wind Friction Depends on pressure gradient force and roughness Slows down the wind and makes it blow at an angle toward lower pressure Direction is opposite the wind direction Anticyclones Centers of high pressure that brings clear dry weather Blue H on the weather map Winds blow clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemi sphere Mid latitude Cyclonic Storms Surrounds low pressure systems Wind blows counterclockwise and inward Forms over the middle latitudes outside of the tropics Forces that affect the horizontal movement of air 1 Pressure gradient force 2 Coriolis force 3 Centripetal force 4 Friction Pressure Gradient The amount of pressure change that occurs over a given distance Acts at right angles to the isobars weak pressure gradient bars spaced out Strong pressure gra dient bars close together Hydrostatic Equilibrium Balance between upward directed pressure gradient force and down ward force of gravity No net vertical force or vertical acceleration Does not exist in violent thunderstorms or tornados Sea Breeze Movement of air from sea to land Usually occurs in the afternoon Cooler air from above the water moves over the land forcing the heated less dense air above the land to rise Land Breeze Surface breeze that flows from the land toward water Usually occurs at night Air above the land becomes cooler than air over the water producing a distribution of pressure Usually not noticed on shore but frequently observed by ships in coastal waters Sea Breeze Front The leading edge of the sea breeze Cooler air from above the water moves over the land forcing the heated less dense air above the land to rise the cold air from above the sea meets the warmer air from above the land and creates a boundary like a shallow cold front El Ni o A warm ocean current that flows along the equator from the date line and south off the coast of Ecuador at Christmas time Brings monsoons hurricanes are not as common during these years Prevailing Winds Global winds that blow constantly from the same direction Greatly affect the climate of the region Hadley Cell The atmospheric circulation cell nearest the equator in each hemisphere Air in these cells rises near the equator because of strong solar heating there and falls because of cooling at about 30 latitude Ferrel Cell Thermally indirect cell in which cool air rises and warm air sinks This cell is formed due to sinking air at 30 degrees and rising air at 60 degrees latitude Single Cell Model Describes the sun remaining fixed at the equator and thus heating that re gion The heated air rises vertically and heads northward to the poles where it cools and heads back to the equators Three Cell Model A generalized description of global scale circulation that calls for three large cells in each hemisphere The cells rotate on a vertical plane with axes parallel to latitude lines thereby moving heat and moisture in a north south direction From the equator to 30 degrees latitude Hadley Ferrel and Polar General Circulation of the Atmosphere Unequal heating of the earth s surface large scale atmospheric motions over the entire earth Northern Hemisphere major ocean currents cause cool waters to travel from the poles to the Equator along the western coasts of continents Warm waters from Equator travel towards the poles along eastern coasts Air Mass Large body of air whose properties of temperature and humidity are fairly similar in any horizontal direction at any given latitude not stationary Defined by its place of origin Polar cold P Tropical hot T Maritime wet w Continental dry c Front The transition zone between two air masses of different densities Usually separate air masses with contrasting temperatures often separate air masses with differ ent humidities as well Warm Front Boundary ahead of a warm air mass that is pushing out and riding over a cold air mass Winds blow perpendicular to the front of the front and parallel to the back of it speed of about 10 knots Moves in a series of rapid jumps During the day mixing occurs on both sides of the front making it move faster At night radiational cooling creates cool dense surface air behind the front inhibiting both lift ing and forward progress Cold Front Cold air advances toward warm air and pushes it up and out of the way cold dry polar air replaces warm moist subtropical air Just before the front passes pressure falls while just behind the front pressure rises Winds blow perpendicular to the back of the front and parallel to the front of it Usually move toward the south southeast or east Occluded Front When a cold front catches up to and over takes a warm front and creates a frontal boundary Part of a much larger storm system the middle latitude cyclone Cold Occlusion The air behind the occluded front is colder than the air ahead of it Cold front rapidly approaches the warm front cold front over takes warm front cold front over
View Full Document
Unlocking...