Weather

Daily Review #6 Today in your car tires what is happening to the pressure due to the weather conditions? Why? What kind of air mass was over us yesterday? Why? Why is there a cool breeze near the ocean during the middle of a hot day? What layer of the atmosphere do we live in? How is that layer heated?

EndFrontsAir masses dont mixFront = boundary between themWhat happens?Warm, less dense air moves upCold, more dense air sinksTypesColdWarmStationaryOccludedType of cloud can tell you what type of front

Air masses dont mix and are moved around by global winds (convection cells) because they air in each is different from another air mass; the boundary between air masses is called a front, not a very wide zone only a few miles wide; often location of clouds, storms and strong windsWhen a front forms: the warm, less dense air rises up and the cold, dense air sinksCold front: when a cold air mass pushes a warm one out of the wayWarm front: when a warm air mass pushes a cold one out of the wayStationary front: neither front moves, both are stalledOccluded: fast moving cold air mass traps warm air between two cold air massesThe clouds present can often tell you what kind of front is present or coming, sometimes you can even see the front as it moves towards you as a wall of clouds2Storms, Lightning and Thunder, oh myStormsWarm, moist air risesCondenses atClouds buildUpdrafts and downdraftsLightning Build up of charge Negative positive Heats up airCauses thunder

TornadoesForm in severe thunderstormsWind at different altitudes is different speedsCreates swirling windsEventually become verticalSwirling cloud reaches ground = tornadoNot on ground for longExtremely low pressureWinds 100-400 mphNot well understoodDamageTornado warnings and what to do

Image: http://www.weatherwizkids.com/weather-tornado.htmPicture: F3 tornado near Willmar in 2008, http://climate.umn.edu/doc/journal/tornadoes080711.htm Tornadoes form inside of cumulonimbus severe thunderstorm clouds that are massive in sizeAs the cloud continues to build areas of high speed wind form above areas of low speed wind which creates an overall pattern of swirling winds, eventually this pattern becomes vertical as the storm cloud continues to buildIf that vertical swirling pattern reaches the ground it is a tornado, not all of these swirling wind patterns reach the groundThe tornadoes themselves are unstable and dont remain on the ground for long, the interior contains very low pressure levels and thus materials are sucked into the tornado vortexWinds can reach from around 100mph to greater than 400mphWe dont thoroughly understand tornadoes because it is hard to get measurements from inside the tornado vortex, the speed of the wind and the low pressure destroy most instruments

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What to look for

Daily Review #7 Why does oil float on water? Why does a paper clip? (Can you make either one sink?) A front has moved into this area. What would be some signs that this has happened? How would you know what kind of front it is? How are tornadoes created? Why are tornadoes so destructive?

EndJet stream

High speed windUpper troposphere, lower stratosphereNo consistent pathEffect weather patterns

Global Wind

Unequal heating at different latitudesEquator (lower latitudes)Warmer airRises, lowers pressureMoves towards polesSinks when cools, higher pressureConvection cellsPatterns of moving air and high/low pressureCreate areas of high and low winds

Jet stream image: http://www.atomstozebras.com/2007/02/24/anatomy-of-a-storm-midwestern-blizzard-february-2007/The tilt of the earth and angle of the sun causes different latitudes to heat differently, some areas are hotter than othersLower latitudes receive more direct sun and thus have warmer temperatures and warmer air, this air rises because it is less dense and creates areas of lower pressure which gest pushed towards the poles where the opposite is happening creating areas of higher pressure as it encounters cooler air it cools and sinks creating higher pressure areas and a cycleThese cyclical patterns are called convection cells with are moving from areas of high pressure to areas of lower pressure this pattern repeats itself as you move north or south creating 6 convection cells globally with these cells come winds moving from high to low pressure areasThe jet stream (there are several that exist at any given time) is completely separate from the winds created by convection cells; it is a high speed wind (100+ mph) in the upper troposphere and lower stratosphere which follows no consistent path (change but can stay in the same general area for long periods of time) but is found between different air masses; effects weather patterns and longer run climate patterns like El Nino10Coriolis EffectWind moves in a straight lineEarths rotationCauses appearance of curvingNorthern Hemisphere = clockwise (right)Southern Hemisphere = counter-clockwise (left)

Top image: http://images.yourdictionary.com/images/science/AScoriol.jpgBottom image: http://science.kennesaw.edu/~jdirnber/oceanography/LecuturesOceanogr/LecCurrents/LecCurrents.htmlDEMONSTRATION with spinning lazy susan with a ball rolling across it, draw on a globe as you rotate itWind moves in a straight line from areas of high pressure to areas of low pressure, north to south or whichever direction, but in a straight lineAs the wind blows in a straight line the Earth underneath it is rotating, this causes the wind to appear to be curving, this causes the wind to appear to curveIn northern hemisphere this curves wind clockwise and southern hemisphere it is counter-clockwiseThis only effects large scale motion of wind and water not small scale like in your sink or toilet; causes wind in storms to curve this way and ocean currents also11CyclonesLarge weather systemsImpacted by Coriolis effectCycloneLow pressurePulls air in and upwardProduces storms

Anti-cycloneHigh pressureAir moves out and downwardClear skies

Air masses can belong to larger groups of organized weather patterns, these are organized over thousands of miles around a center of high or low pressureBecause they such large movements of wind, they are impacted by the Coriolis effectCyclone: forms around an area of low pressure, air moves inward, direction dictated by Coriolis effect and what hemisphere it is located in, at the center the air is pushed upward because of increasing pressure at the bottom of the storm; rising air creates clouds and thus stormsAnti-cyclone: forms around an area of high pressure, air moves outward and downward and is associated with areas of fair skies and no precipitation12Daily Review #8 What are the 3 major conditions needed for clouds to form? What is the Coriolis effect? What is the jet stream? How are lightning and thunder created? What from this unit can you use to describe/explain our weather this weekend?

EndHurricanesWinds at least 74 mphForm over tropicsWarm, moist air forms cloudsRotatingMore water evaporatesCreates low pressure eyeLacks windGets larger with more evaporationLoses energy once it hits landNo more fuelCyclones, typhoons, hurricanes

Picture: Hurricane Ivan 2004, http://www.noaanews.noaa.gov/stories2005/s2438.htmImage: http://spaceplace.nasa.gov/hurricanes/Hurricanes are large, rotating weather systems with winds at least 74mph (below that they are tropical storms or tropical depressions); they can be 150-1500km in diameterThey form between 5 and 20 degrees north or south of the equator, they need extreme heat and moisture from that area to evaporate, rise and form clouds by condensing as it rises and contacts cooler airAs more water evaporates and rises, it forms circular patterns which are rotating in the direction dictated by the Coriolis effectAs it stays over warm water, more water evaporates and the clouds build and a low pressure area, eye, forms which has air moving upward, but no outward moving air so it lacks surface winds; the size of the storm continues to build as long as it remains over the waterOnes it is pushed towards the land, the storm no longer has fuel (water) and it loses energy, turning into tornadoes or severe thunderstorms but eventually that too runs out of energy and dies offIn the Atlantic and Northeast Pacific, the term hurricane is used. The same type of disturbance in the Northwest Pacific is called a typhoon and cyclones occur in the South Pacific and Indian Ocean.14