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general circulation
the largest-scale patterns, the background against what unusual events occur
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single-cell model
a simple circulation pattern, describes th egeneral movement of the atmosphere
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zonal winds
winds blowing east to west or west to east
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meridional winds
winds moving north to south or south to north
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three-cell model
a more elaborate model used to describe the general atmosphere that divides the circulation of each hemisphere into three distinct cells (Hadley cell, Ferrel cel, and polar cell)
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Hadley cell
circulates air between the tropics and subtropics
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Ferrel cell
circulates air in the middle lattitudes
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Polar cell
circulates air around the poles
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equatorial low (Intertropical Convergence Zone[ITCZ])
A zone of low pressure around the equater created by strong solar heating, wich causes air to expand upward and diverge toward the poles.
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subtropical highs
When air in the Hadley cell sinks toward the surface it forms subtropical highs, which are large bands of high surface pressure.
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horse latitudes
the point at which horses were thrown overboard from ships crossing from Europe to the New World in order to not get stranded.
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northeast trade winds
winds deflected slightly to the right by a weak coriolis from the subtropical highs
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southeast trade winds
In the southern hemisphere, the northward-moving air from the subtropical high is deflected to the left to create the southeast trade winds
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subpolar lows
areas of low pressure
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westerlies
a wind belt created by air going poleward undergoing a substantial deflection to the right
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polar highs
low-level anticyclones of the arctic and antarctic
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polar easterlies
low-level winds originating in the polar highs
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semi-permanent cell
high and low-pressure cells that undergo seasonal changes in position and intensity throughout the year
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Aleutian and Icelandic lows
cells over the Pacific and Atlantic Ocean
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Siberian high
cell over central Asia
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Hawaiian and Bermuda-Azores high
cells over Pacific and Atlantic oceans
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Tibetan low
cell over southern Asia
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polar front
a boundary between warm and cold air
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polar jet stream
maintains the temperature contrast across a front, a consequence of a polar front, like a river of air
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subtropical jet stream
jet stream near the equator, associated with the Hadle cell
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Rossby waves
waves are wavelike flows of air caused by ridges and troughs... Rossby waves are long waves
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ocean currents
horizontal movements of surface water often found around the rims of major basins
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Ekman spiral
An ocean current pattern in which 100m below the surface the direction of the current approaches 180 degrees to the directionof the wind, and thus dies out.
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North Equatorial Current
Just north of the equator, the easterly trade winds drag the surface water westward to form the North Equatorial Current
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South Equatorial Current
Just south of the equator, easterly trade winds drag the surface water westward
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Equatorial countercurrent
the water from the north and south equatorial currents converges and piles up in the western equatorial Atlantic and forms the eastward-moving Equatorial countercurrent
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Gulf Stream
In the Northern Hemisphere, most of the North Equatorial Current reaching the South American coast turns northward to form the Gulf stream
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North Atlantic Drift
Near 40 degrees N., the westerlies force the current to the east, forming the North Atlantic Drift (as opposed to the Gulf Stream)
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Canary Current
The North Atlantic Drift eventually cools to become the cold Canary Current as it turns southward
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Labrador current
the cold current that flows southward along the Maritime Provinces of Canada
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East and West Greenland Drift
feeds the Labrador Current along the Maritime Provinces of Canada
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upwelling
strong offshore winds (from land to ocean) drag warmer surface waters seaward, which draws up cooler waters from below to take their place
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global scale
large-scale features of the atmosphere
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synoptic scale
features that cover hundreds or thousands of square kilometers (smaller than global scale features) operate from days to a couple weeks
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mesoscale
smaller features than both global scale and synoptic scales, consists of elements covering tens of square kilometers and last as breif as half an hour
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microscale
the smallest exchanges of mass and energy scale
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monsoon
the climatic pattern in which heavy precipitation alternates with hot, dry conditions on an annual basis
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monsoon depressions
areas of low pressure superimposed in the southeasterly air flow out of Bay of Bengal.
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Foehn (pronounced "fern")
generic name for synoptic scale winds that flow down mountain slopes, warm by compression, and introduce hot, dry and clear conditions to the adjacent lowlands
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chinooks
winds warmed by compression that descend the eastern slopes of the Rocky Mountains
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Santa Anna winds
develop (in California) when high pressure develops over the Rocky Mountains, the descends the western slopes and are warmed by compression.
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katabatic winds
originate when air is locally chilled then flows down slopes and is warmed (unlike foehns and chinooks, which are cooled by migration of weather systems)
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sea breeze
the air from water moves toward low-pressure area over land (remember, winds are always named after the direction from which they blow)
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sea breeze front
a distinct boundary between the cooler maritime air and the continental air it displaces
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land breeze
when the land surface cools more rapidly than the water at night, the air over the land becomes dense and creates a land breeze.
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lake breezes
much like sea and land breeze circulations, but with lakes
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valley breeze
air flows up from valleys to replace the warm air on top of slopes that expand outward
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mountain breeze
at night, mountains cool more rapidly than low-lying areas, so the air becomes denser and sinks into the valleys to produce mountain breeze
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El Nino
recurrent event in the tropical Eastern Pacific in which sea surface temperatures are significantly above normal
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Walker Circulation
east-west circulation pattern of the tropics
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southern Oscillation
the change in sea surface conditions linked with the change in the atmospheric pressure distribution
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ENSO events
the combined occurrence of El Nino and Southern Oscillation (because they are closely intertwined)
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La Nina
(opposite of El Nino) below normal sea surface temperatures exist in the tropical eastern Pacific
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Southern Oscillation Index (SOI)
the monthly sea-level departure from normal at Tahiti minus the departure from normalk at Darwin, Australia.
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teleconnections
the relationship between weather or climate patterns at two widely separted locations
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Pacific Decadal Oscillation
a pattern in which two nodes of sea surface temperature exist (a large on in the norther and western part of the basin and a smaller one in the eastern tripical Pacific)
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Arctic Oscillation and North Atlantic Oscillation
The multiyear oscillations of the Atlantic
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