# Shared Flashcard Set

## Details

Weather and Climate - Test 3
Weather and Climate - Test 3
49
Geography
10/18/2008

Term
 air pressure
Definition
 -mass of air above a given level -it takes a shorter column of cold, more-denseair to exert the same surface pressure as a taller column of warm, less dense air  -warm air aloft is often associated with high atmospheric pressure, and cold air aloft is associated with low atmospheric pressure -heating and cooling columns of air can establish horizontal variations in air pressure; both aloft and at the surface.... this causes winds to blow
Term
 measuring air pressure (3)
Definition
 BAROMETER - detect and measure pressure changes MERCURY BAROMETER - invented by stendent of Galileo... vaccume inside and sucks up mercury from a dish ANEROID BAROMETER - most common type... contains no fluid (aneroid cell in vaccume contracts with air pressure)
Term
 bar
Definition
 -unit of pressure that describes force over a given area millibar - most common unit of pressure... (equal 1/1000 of a bar)
Term
 standarm atomspheric pressure/sea-level pressure/station pressure
Definition
 SAP - 1013.25mb =1013.25 hPa = 29.92 inches Hg- this is sea level pressure Station Pressure - acquired after recorded pressure is corrected for temperature, gravity, and instrument error Sea-level pressure - corrected for T, gravity, instrument error, and altitude
Term
 isobars
Definition
 -lines connecting points of equal pressure... 1000mb is base.. drawn at interval of 4mb ******near earth's surface, atmospheric pressure decreass approximately 10mb for every 100m increase in elevation (1 inch Hg per 1000ft)
Term
 anticyclones/mid-lat cyclones
Definition
 ANTI- centers of high pressureMID LAT - centers of low pressure, also called depressions, or extratropical cyclones
Term
 isobaric map
Definition
 -uppoer air map... is a constant pressure chart... shows height variations at given pressure (500mb)
Term
 contour lines/isotherms
Definition
 -lines that connect points of equal elevation-contour lines of low height = low pressure-high height = high pressure-typically decrease in value from north ot south ISOTHERMS- lines of equal temperature... show ridges and troughs
Term
 Newton's Laws of Motion
Definition
 1)any object at rest will remain at rst and any object in motion will remain in motion.. so long as no force is exerted upon it 2)force exerted on object is equal to its mass times its acceleration (F=ma)
Term
 Forces that affect where the wind will blow
Definition
Term
Definition
 pressure gradient - difference in pressure over distance...... steep pressure gradients are a rapid change in pressure over short distances.... shown with very close isobars Pressure Gradient Force - is directed from higher to low pressure at 90 degree angles to isobars... magnitude is related to pressure gradient-this is the force that causes wind to blow
Term
 Coriolis Force
Definition
 -apparent force due to rotation of the earth-causes wind to deflect to riht  in NH and left in SH**the stronger the wind the greater the deflection  -coriolis effect is most strong at the poles (and none exactly over the equator Amount of deflection depends on:1)rotation of the earth2)latitude3)object's speed **only influences wind direction, not wind speed  ***coriolis effect varies with the sine of latitude (sine0=0, sine90=1)
Term
 geostrophic wind
Definition
 -theoretical horizontal wind blowing in a straight path, parallel to isobars or contours, at a constant speed. The geostrophic wind results when coriolis force balances horizontal pressure gradient force
Term
 cyclonic flow
Definition
 -counter clockwise flow of air around a low
Term
Definition
 -blows at constant speed parallel to curved isobars
Term
 centripital force
Definition
 -radial force required to keep an oject moving in a circular path.. it is directed to the center of that curved path
Term
 meridional
Definition
 -wind-flow pattern where wind flows in large looping meanders, following North-South trajectory
Term
 zonal wind flow
Definition
 -a wind that has a predominant west-to-east component
Term
 friction layer
Definition
 -atmospheric layer affected by friction (usually up to 1 km)-near surface, friction reduces wind speed, which in turn reduces the effect of the coriolis force-coriolis no longer balances PGF and wind blows across isobars (approx 30 degrees) toward low pressure -if convergence/divergence in pressure system are not equal, pressure will change
Term
 hydrostatic equilibrium
Definition
 -state of atmosphere when there is a balance between the vertical PGF and downward pull of gravity
Term
 Kinds of wind (4)
Definition
 1)onshore wind - wind blowing from water onto land2)offshore wind - wind blowing from land to water3)upslope wind - wind blowing downhill from uphill4)prevailing wind - wind direction most often observed during a given period of time-these can greatly affect climate in a region
Term
 Measuring Winds (6)
Definition
 1)wind nose - indiates percentage of time that wind blows from a certain direction2)wind vane - old and reliable way of determining wind direction3)anemometer - measures wind speed... by rates of rotating cups4)aerovane - indicates speed and direction (propellor)5)radiosonde - can measure its angles to learn about wind.... called RAWINSONDE OBSERATION6)wind profiler - doppler radar used to profile wind
Term
 Scale of Motion
Definition
 -hierarchy of motion from tiny husts to giant storms MICROSCALE -a few meters across or less (small turbulent eddies)MESOSCALE - circulation within 20 km (thunderstorms, tornadoes, dust devils, hurricanes, tropical storms, land/sea breeze, mountain/valley breeeze, etc)
Term
 eddy
Definition
 -when the wind envounters a solid object, it is the whirld of wind that forms on object's downward side **Rotors are large eddies formed by mountains
Term
 Wind shear
Definition
 -wind changes speed or direction abruptly
Term
 CAT
Definition
 clear air turbulence-eddies formed in clear air
Term
 thermal circulations
Definition
 -circulations brought on by changes in air temperature in which warmer air rises and colder air sinks
Term
 sea/land breeze
Definition
 -sea- occurs during the day, when land warms and air rises... a PGF is established and cooled ocean air flows on land land - occurs at night, and is basically the opposite Sea Breeze Front - the leading edge of a sea breeze, and is followed by a rapid drop in temperature-sometimes appears smokey or foggy
Term
 mountain/valley breeze
Definition
 -mountain - occurs at night, cooler dense air glides down mountain.. also called gravity winds or nocturnal drainage  valley - during day, warm and gentle upslope wind up mountains  *** these both are best noticed when prevailing winds are light in clear summer weather
Term
 monsoon wind system
Definition
 -one that changes direction seasonally-winter monsoon means clear skies, with winds from land to sea-summer monsoon yields wet and rainy weather, with winds from land to sea Cherrapunju- gets recordrrain in summer, and almost none in winter. agerages 1080cm/yr
Term
 Katabatic wind
Definition
 -downslope winds much stronger than mountain breezes-very cold snowy air triggered to flow downhill-can be extremely strong, usually high initial potential energy
Term
 chinook winds
Definition
 -warm and dry wind that decends the eastern slope of the rocky mountains-main cause is the decending compressional heating -called foehn winds in other parts of the world
Term
 Santa Ana Wind
Definition
 -warm dry wind that blows from east or north-east into southern california-caused by high  pressure zone in dsert ... it pushed hot winds-again, compressional heating as it decends-sets stage for serious brush fires
Term
 haboob
Definition
 -spectacular storm composed of dust or sand-caused by thunderstorm downdrafts
Term
 dust devil
Definition
 -spinning vortica commonly seen on hot days in dry areas-heated surface, air rises, then is spinned by wind-can spin in either direction
Term
 assumptions for the single cell model
Definition
 1)the earth's surface is uniformly covered with water (so that differential heating between land and water does not come into play) 2)the sun is always directly over the equator (so that the winds will not shiftseasonally( 3)the easth does not rotate (so that the only force we need deal with is PGF)
Term
Definition
 -cell of circulation driven by sun
Term
 doldrums
Definition
 -region over equatorial waters where air is warm, horizontal pressure gradients are weak, and winds are light -weather in this area is monotonous
Term
 subtropical highs
Definition
 -high pressure and dry zones @ around 30 degrees
Term
 polar front
Definition
 a semipermanent, semicontinuous front that separates tropical air masses from polar air masses
Term
 farrel cell
Definition
 the middle cell (30-60)
Term
 pressure systems to know
Definition
 JULYBermuda High/Pacific High - ocean high pressure zones that remain constant all year Icelandic low/Aleutian low - cyclonic low pessure zones activity represent where numerous storms tend to converge JANUARYSiberian High -formed by very intense cooling of land
Term
 jetstreams
Definition
 -where upper level winds tend to concentrate into narrow bands of fast flowing air -usually found at tropopause  subtropical jetstream- situated near 30 lat polar front jet streatm - approx 60 lat.. over polar front **jetstreams play a major role in global heat transfer
Term
 upwelling
Definition
 -as wind blows paralell to the coast, water is pushed seaward and cold/nutrient rich H2O replaces
Term
 ENSO
Definition
 EL NINO-reversla of current flow due to reversal of Hadley cells... brings warm water to Peru ratherthat the usual nutrient rich and cold antarctic water-chokes off upwelling near Peru-every few years, surface atmospheric pressure systems change-strengthens the equatorial counter current that goes towards S America SOUTHERN OSCILATION-see saw pattern of reversing surface air pressure at opposite ends of pacific ENSO- same thing, as El Nino and Oscillation are simultaneous-air rises now near Peruand sinks off coast of Australia... now rains/droughts in different places
Term
 La Nina
Definition
 -unusually strong regular conditions
Term
 teleconnections
Definition
 -a linkage between weather changes occuring in widely separated regions of the world
Term
 NAO/AO/PDO
Definition
 NAO-North Atlantic oscilaation - pressure reversal over atlantic AO-arctic oscillation PDO- Pacific Decadial oscillation (every 20-30 years)
Term
 the gas law
Definition
 pressure = temperature X density X a constant
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