Unit of measure expressing force per surface areamillibarsIsolines of equal pressure Contours reveal locations of high and low pressureIsobarsHorizontal rate of pressure change Spacing of contour lines reveals pressure "slopes"pressure gradientsAreas of pressure relatively higher or lower than surroundings -Elongated area of relatively high pressure -Elongated area of relatively low pressureHighs or Lows Ridge TroughHorizontal air movement...wind_____ of Earth's surface creates temp gradients that create pressure gradients ____ set air in motion as wind Generally, wind blows from areas of ____ to areas of ____. It is rarely a straight flow; other forces alter wind's direction.uneven warming pressure gradients from higher pressure to lower pressureWind direction is the result of 3 interacting forces. What are they?1. Pressure Gradient Force (PGF) 2. Coriolis Force/Effect 3. FrictionWind moving from high to low pressure...it rarely acts on wind alone...Pressure Gradient Force (PGF)Wind's path is deflected due to Earth's rotation... Northern hemisphere deflects ____ Souther hemisphere deflect ____ Only affects ____, not speed.Coriolis Force/Effect NH deflects right SH deflects left Only affects direction, not speedUpper atmosphere winds only influenced by pressure and Coriolis...Geostrophic WindsThe drag of Earth's surface... Slows wind, reducing Coriolis Influence is greatest at the surface; diminishes with increasing altitudeFrictionExtending only about 1000 meters (3300 feet)...above this layer, winds follow the Geostrophic course...Friction Layer / Boundary LayerDetermined primarily by pressure gradient.... Variable by location and season -Steep gradients create _____. -Gentle gradients create ____.wind speed -steep = faster wind speeds -gentle = slower wind speedsHigh-pressure center with anticyclonic air flow Low-pressure center with cyclonic air flowAnticyclone CycloneWhat is the NH upper-air pattern?-Anticyclonic geostrophic clockwise flow -Cyclonic geostrophic counterclockwise flowWhat is the NH friction-layer pattern?-Anticyclonic divergent clockwise flow -Cyclonic convergent counterclockwise flowWhat is the SH upper-air pattern?-Anticyclonic geostrophic counterclockwise flow -Cyclonic geostrophic clockwise flowWhat is the SH friction-layer pattern?-Anticyclonic divergent counterclockwise flow -Cyclonic convergent clockwise flowVertical Movement: -_____ = sinking air, high pressure, surface divergence, clear cloudless skies - _____= rising air, low pressure, surface convergence, clouds precipitation and storms-Anticyclone -CycloneWhat are the characteristics of the Hypothetical Circulation Pattern of a non-rotating Earth (4)? -Assumes non-rotating, uniform Earth surface, no distinction between landmasses or oceans.1. Consistent solar heating at equator -thermal low pressure band -rising air over low latitudes 2. Cooling at highest latitudes -develop caps of high pressure over poles -sinking air over poles 3. Surface winds would blow equator-ward 4. Geostrophic winds would blow pole-wardTwo tropical convection cells situated on either side of the equator.... -Around equatorial lats, warm air rises, producing region of relatively ____ surface pressure. -Air aloft cools, forming ____ or ____ -Air descends around ____ N/S, forming high pressure.Hadley Cells -warm air rises --> region of low surface pressure -air aloft cools --> clouds or storm -air descends around 30degrees N/S --> high pressureSeven Components of General Circulation....1. Intertropical Convergence Zone (ITCZ) 2. Trade winds 3. Subtropical highs 4. Westerlies (winds) 5. Polar front (Subpolar lows) 6. Polar easterlies (winds) 7. Polar highsLarge semi-permanent anticyclones near 30degrees N/S -Develop from descending air of _____ Cells -Elongated, east-->west cells located over ocean basins where conditions are somewhat constant (broken up by land masses that develop ____ pressure) -Subsidence, as gentle downdrafts, creates ____ -Weather is consistently clear, warm, and dry -Location of Earth's major ____. -Absence of wind know as ____.Subtropical high (STH) -Hadley Cells -low pressure -subsidence temperature inversions -deserts -Horse LatitudesMajor wind system of the Tropics... -Diverging ____ from sub-tropical highs. -Exist between ____ N/S -NH winds blow ____ -SH winds blow____ -Reliability of winds due to consistent direction and speedTrade Winds -equator-ward -25degrees N/S -NH northeast -SH southeastTrade Winds are ____ and ____. -They move over ____, evaporating water. -They do no produce ____ unless forced to rise. -If they rise, the produce tremendous ____ and ____ conditions.dry and warm -move over oceans -do not produce rain -precipitation and storm conditions *some of the wettest places on Earth are mountainous islands in the trade winds' path (Eastern Hawaii)Zone of convergence of Trade Winds.... -Shifts to hemisphere experiencing Summer -More pronounced over ____ -Warm surface conditions, ____ pressure, and ____ skies. -Generates high rain fall and energy transfer into upper atmosphereIntertropical Convergence Zone (ITCZ) -More pronounced over land -Warm surface, low pressure, cloudy skiesZone of weak horizontal flow (ITCZ)....DoldrumsWinds of the midlatitudes.... -Flow out of ____ polewards between ____N/S to ____N/S -Less constant and persistent -Do not always flow from the west. Why?Westerlies -Flow out of STHs, between 30degrees N/S and 60degrees N/S -Surface interruptions & modifications due to friction, topographic barriers, and migrating pressure systemsTwo zones of fast-moving geostrophic Westerlies.... -Each located in upper troposphere over area of greatest temp gradient -_____ = poleward boundary of Westerlies -_____= equator-ward boundary of WesterliesJet Streams -Polar front jet stream = poleward -Subtropical jet stream = equator-wardCurves that develop as high-altitude Westerlies flow North and South... -Separate cold polar air and warmer tropical air -typically "zonal flow" along parallels -can shift to "meridional flow," bringing cold air equator-ward, warm air poleward -Meridional flows can produce frequent and severe ____ changes in midlatitudesRossby Waves -severe weather changes in midlats In this photo... -Zonal (far left) West-->East -Meridional (far right) West--> North/South -->EastHigh-pressure cells develop over poles...Polar Highs -extensive, cold, sinking air and anticyclonic winds -stronger over Antarctic landmass -shifting of Arctic high to land in WinterWinds flowing East to West...Polar Easterlies -diverge from polar high -cold and dryZone of low pressure between 50degrees N/S and 60degrees N/S -also the location of semipermanent _____ -air mass conflict between warmer Westerlies and colder Easterlies -more pronounced over polar circles' oceans -characterized by ____ air, cloudiness, and precipitation -source of migratory storms in midlats -polar jet stream position often along this ....Polar Front -Converging air masses = a front (Easterlies --> [front] <-- Westerlies) -Subpolar Lows -rising air, cloudiness, and precipitationSeasonal variation in location (shift of all 7 components N/S with seasons) -Shift North in NH during ____ -Shift South in SH during ____ -Displacement is greatest at ____ lats, and the least at the ____-during Summer -during Summer -displacement at low lats, least at the PolesThe ITCZ shifts as far as ____N in July and ____S in January.shifts to 25degrees N in July 20degrees S in January -Shifts in circulation impact weather in tropics and midlatsSeasonal reversal of winds and precipitation patternsmonsoons -Unequal heating of land and ocean is intensified by shifts in ITCZ and location of subtropical jet stream -Populations rely on rains for food production -major monsoons: India, China -minor monsoons: Australia, West AfricaSummer ____ brings heavy rains from oceans Winter ____ is dry continental airOnshore Flow Offshore FlowDaytime onshore winds....Sea breezes -water heats slowly during the day -wind flows from thermal high over sea to thermal low on landWeaker nighttime offshore winds....Land breezes -land cools off faster at night -wind flows from thermal high over land to thermal low over seaDaytime upslope flow... -Heating of high-elevation land causes air to rise, creating thermal low -Cooler air from valley floor flows upslope toward thermal lowValley breezeNighttime downslope flow... -Slopes radiate heat away; cool air forms thermal high -Cooler, denser air flows as downslope winds into valleyMountain breezeDownslope winds develop from pressure gradients across topographic barriers.... -air flows across pressure gradient and warms from latent heat of condensation and adiabatic warming -leeward flow is warm and dryFoehn (or Chinook) WindsDevelop out of stationary high pressure in interior of Western United States.... -diverging winds bring dry, warm air to coast -known for high speed, high temps, and dryness -responsible for many California wildfiresSanta Ana WindsEpisodic atmospheric and oceanic phenomenon of atypical warming of eastern equatorial Pacific.... -abnormally warm water appears at surface along west coast of South American, replacing cold, nutrient-rich waters -typically occurs every 3-7 years for about 18 months -brings changes in global pressure, wind and precipitation. how?El Niño -fisheries get disrupted -rains are heavier in some areas, drought afflicts othersConvection cell of equatorial Pacific.... Reverse of El Niño -STH at west coast of South America: -Westward Trade Winds and warm equatorial currents -coastal cold water upwelling and dry air -Western Pacific affected by ITCZ: -warm surface waters and high precip. -rising air aloft as upper-atmosphere "antitrade winds"Walker CirculationDescribe the El Niño Souther Oscillation (ENSO)....-Onset Trade Winds pile up warm water in western Pacific that spreads east -On west coast of South America, warm water pools, STH weakens, and upwelling halts -Ocean temps rise further -Trade Winds weaken and may reverse directions; ITCZ also shifts -More rain develops on subtropical coasts -Coastal Australia and Indonesia in drought, monsoon affectedOpposite of El Niño, as atypical cooling of waters off South America Strengthened Walker Circulation -Trade winds stronger, water off Indonesia warmer -SW U.S. drier, around Indonesia wetter -Not just an opposite swing from El Niño; does not always developLa NiñaDescribe ENSO variability.... What are OATs?-Unclear whether starts off with a change in pressure or ocean temp -Also evidence of other ocean-atmospheric cycles at work -Teleconnections (OATs) = relationship between weather and oceanic events in different areas of the globe -extent of weather changes is difficult to predicts What we do know is that El Niño is becoming more frequent and warmer (climate change)