1、Weather FactorslComposition of Airl78%Nitrogenl21%Oxygenl1%Other(trace gasses)Permanent Proportions=Carbon Dioxide,Ozone,Neon,Argon,HeliumVariable Gases=Water Vapor(0-4%)Ozone(O3)located 50,000-100,000-blocks UVslP/DT=RThe temperature around the globe is a result of the tilt,rotation,and orbit of th
2、e earth around the sun.Heat transfer is affected by terrestrial radiation,conduction,and convection/advectionWhy the temp rise?*Ozone absorbs solar radiation*Troposphere:Lowest level of atmosphere less at poles bulges at equator Average=37,000 thick Temperature decreases with altitude(positive lapse
3、 rate)Most weather occurs in troposphere 99.5%of water in troposphere Tropopause Boundary level-acts as lid to keep water in troposphere Lower near poles,higher near equator Lower in winter,higher in summer Little temperature change(neutral lapse rate)Most weather(clouds)do not penetrate this layer
4、Contains turbulence,jet streams,and high thunderstorms Stratosphere:Starts about 66,000 and is 15 miles thick Temperature increases with altitude(negative lapse rate)High concentration of ozone Air is stable,very little weather Stratopause:Boundary level between stratosphere and mesosphere Approxima
5、tely 160,000 high Mesosphere:Temperature once again begins to drop with altitudelDifference in pressure between two points divided by the distance between the pointslCirculation is due to Convection.lAs temperature rises,molecules spread apart.lLess dense air moves upward(convection).lAn area of low
6、 pressure is left behind.lHigher pressure air moves in to fill the void(advection).lIsobars lines of equal pressurelPressure Gradient-change in pressure over distanceWide or dashed is weakClose spacing is stronglRule of Thumb but not always:High pressure-descending air/good wxLow pressure-ascending
7、air/worse wx Northern Hemisphere:A mass traveling great N-S or S-N distances,ie.Rockets,Oceans,Air Masses,will deflect to the right.Southern Hemisphere:opposite effect.lEarth Spins on Axis(1 revolution in 24 hours):lPoles rotate in space.lAt same time,a spot on equator travels 25,000 miles(1040 mile
8、s per hour).lIf we stand on top of the north pole and throw a baseball toward China,it will take time for the baseball to get to China.lWhile the ball is on its way,the Earth continues to rotate.lBy the time the ball gets to where we threw it,the earth has moved.lBecause the earth moved out from und
9、er the ball,the ball lands in the ocean.Not in China.lIf we look at the path the ball took across the ground,it will have curved to the rightl1.in the northern hemisphere,the geostrophic wind is parallel to the isobars with the lowest pressure on the left.l2.the closer together the isobars,the stron
10、ger the pressure gradient/geostrophic wind speed.l3.In the Northern Hemisphere,winds tend to blow counterclockwise around low pressure centers and clockwise around high.l4.geostrophic balance does not occur in small scale circulations such as sea breezes,thunderstorms,tornadoes,and dust devils becau
11、se pressure gradient force is greater here than coriolis.l1.winds increase with altitude in the atmospheric boundary layer,with the greatest increases just above the surface.l2.the wind changes direction clockwise(veers)with increasing altitude.l3.when winds near the surface are strong,the boundary
12、layer is turbulent and winds are gusty.As you descend into the boundary layer to land on a windy day,the air becomes rougher as you get closer to the ground.l4.The boundary layer is deeper during the day and in the warmer months of the year.It is shallower at night and during the colder months.l5.wh
13、en winds are strong,the boundary layer is deeper over rough terrain.l6.Winds near the ground tend to spiral counterclockwise into a cyclone and spiral clockwise out of anticyclones.lStrong accelerations and vertical development can produce quick and large pressure gradients.Examples include wind acc
14、elerating over hills,and down drafts from rain.Convection Orographic Convergence/Divergence Frontal Based upon the difference between the adiabatic lapse rate of a parcel of air compared to the ambient lapse rate of the surrounding air.lFriction from the surface slows air blow it and causes it to tu
15、mblelBased upon lapse rateslStandard:2C per 1000lDry:3C per 1000lMoist:1.2C 2.8C per 1000lAdiabatic Cooling/warming:lChange in temperature due to a change in pressurelAs air rises,it expands and cools.Adiabatic coolinglLapse ratesDALR -3 C/1000SALR -VariableIf lower than ambient,then unstableStandar
16、d Lapse Rate-2C/1000lTemp inversion occurs in stable airlEvaporation-heat is added to water,changing it to a gaslSublimation-ice directly to water vaporlCondensation-air becomes saturated,and water vapor in air becomes liquidlDeposition-water vapor freezes directly to icelAmount of water vapor air c
17、an hold decreases with air temperature.lDewpoint temperature is full saturationlFrostDewpoint is below freezing,and the surface is below dewpointWater vapor depositionlLatent heat of evaporationHeat to vaporize 1 gram of water(540 cal)lLatent heat of condensationWater vapor gives back heatViolent en
18、ergy is released when thousands of tons of moisture condense into a thunderstorm cloudLatent Heat and Stability When air becomes saturated and cloud formations occurs,heat is released when water turns from a vapor to a liquid(condensation).This is important when air is rising and cooling adiabatical
19、ly the stability can be changed due to this latent heat.Adibitaic cooling can be somewhat offest from latent heat.Revision 1.0Formation of Fog/Clouds:A cloud is the visible collection of suspended water or ice particles in the air.Fog is a cloud near the earths surface.Formed by:(requires there to b
20、e water vapor,condensation nuclei)Air is cooled to its dew point.(through adiabatic expansion or cold surface contact)Moisture is added to air until saturation occurs.Condensation nuclei Microscopic particles such as dust and salt that provide a surface for water to form on.Examples are fog forming
21、on populates near cities.Sierra Academy of AeronauticsInternational Training CenterPrivate Pilot Ground CourseRevision 1.0Fog:Steam Fog Upslope Fog Precipitation Fog Advection Fog Radiation FogSierra Academy of AeronauticsInternational Training CenterPrivate Pilot Ground CourseRevision 1.0Steam Fog:
22、Very cold,dry air moves over warmer water.Air near water surface picks up moisture due to evaporation and heat.This warmer,moist air rises,cools,and reaches its dewpoint.Sierra Academy of AeronauticsInternational Training CenterPrivate Pilot Ground CourseRevision 1.0Upslope Fog:Warm,moist air is pus
23、hed up sloping terrain by wind.Air cools adiabatically to dewpoint.Sierra Academy of AeronauticsInternational Training CenterPrivate Pilot Ground CourseRevision 1.0Precipitation Fog:Warm rain falls through cold air.Air picks up moisture from evaporation and quickly reaches its saturation point.Sierr
24、a Academy of AeronauticsInternational Training CenterPrivate Pilot Ground CourseRevision 1.0Advection Fog:Wind blows warm,moist air over a cooler surface.Air near surface is cooled to its dewpoint.Sea Fog:Warm,moist air from a warm sea flows over a colder sea.Sierra Academy of AeronauticsInternation
25、al Training CenterPrivate Pilot Ground CourseRevision 1.0Radiation Fog:Moist air is heated during day.Nighttime terrestrial radiation cools earth and nearby calm air to dewpoint.Valley Fog Ground Fog Ice FogSierra Academy of AeronauticsInternational Training CenterPrivate Pilot Ground CourseRevision
26、 1.0 Valley Fog:Air is moist due to rivers or lakes,calm air pools in valleys.Ground Fog:Occurs after rain or moist earth is cooled.Ice Fog:Radiation fog in artic regions where dewpoint is-25 F or colder.Radiation Fog:Cloud heights,amounts,and type Cloud height or ceilings is defined as the eight ab
27、ove the earths surface of the lowest layer reported as broken or overcast,or as the vertical visibility into an indefinite ceiling.Cloud amounts-measured in eights of the celestial dome.type of cloud is on the basis of what the cloud looks like in its height,shape,and behaviorlFour Groups or Familie
28、sLow(surface to 6500AGL)Middle(6500 to 20,000AGL-alto)High(above 20,000AGL)Extensive Vertical DevelopmentlNamesCumulus Stratus Nimbus CirruslDrizzlelRain/rain showerslSnow/snow showers/snow grainslIce pelletslHaillJust because there is%100 saturation doesnt mean there will be precipitation,most clou
29、ds dont precipitate.l1.Precipitation particles must be much larger than cloud particles so they can fall out of the cloud and exist long enough to reach the ground.l2.Most of the time,processes that produce small cloud particles are not very effective in producing large precipitation particles.l3.Ef
30、ficient precipitation producing processes mainly occur in certain cloud types(usually Nimbostratus and cumulonimbus.lTwo processes by which precipitation forms-condensation/deposition and collision/coalescence.lWater droplets that have coalesced!lVirgaLow relative humidityEvaporates before contact w
31、ith groundlSupercooled waterRemains liquid though cooled freezingTurns to ice or freezing rainlBoundary between air masseslFrontal passage changes:TemperatureWind directionWind speedlFactors affecting intensity:1)moisture 2)stability of lifted air3)speed 4)slope 5)moisture&temp variations 6)surface
32、over which it moveslCold,dense,stable air moves into an area of warm,lighter,unstable air.lForces less dense,warm air up.lFast movingsteep slope due to frictionlSlow movingleading edge much shallowerfair weather cumulus behindlWarm air moves over cooler air at the surface.lSlower moving than cold fr
33、onts.lClouds determined by stability and moisture content.If warm,moist,stable:stratus and steady rainIf warm,moist,unstable(lifted):cumulus and showery rainlStationaryOpposing forces of 2 air masses balance each otherlOccludedFast moving cold front catches up to a slow moving warm frontWeather depe
34、ndent on temperature differenceslStages(Fig 9-23 and 9-24)Pre-DevelopmentIncipientOccludedDissipatinglExtended over a period of days.lTropopause height is about 37,000.lTo 66,000 the temp is-57C in standard atmosphere.lJet StreamSpeed range between 60 and 240 knotsOccur at breaks in the tropopauselSummer-north and weakerlWinter-south and stronger
