仪表等级飞行员理论培训stage3-214A WX FACTORS

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1、Weather Factors lComposition of Airl78% Nitrogenl21% Oxygenl1% Other (trace gasses) Permanent Proportions = Carbon Dioxide, Ozone, Neon, Argon, Helium Variable Gases = Water Vapor(0-4%)Ozone (O3) located 50,000-100,000- blocks UVs lP/DT=R The temperature around the globe is a result of the tilt, rot

2、ation, and orbit of the earth around the sun.Heat transfer is affected by terrestrial radiation, conduction, and convection/advection Why the temp rise? * Ozone absorbs solar radiation * Troposphere: Lowest level of atmosphere less at poles bulges at equator Average = 37,000 thick Temperature decrea

3、ses with altitude (positive lapse 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 we

4、ather (clouds) do not penetrate this layer 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 l

5、evel between stratosphere and mesosphere Approximately 160,000 high Mesosphere: Temperature once again begins to drop with altitude lDifference in pressure between two points divided by the distance between the points lCirculation is due to Convection.lAs temperature rises, molecules spread apart. l

6、Less dense air moves upward (convection).lAn area of low pressure is left behind.lHigher pressure air moves in to fill the void (advection). lIsobars lines of equal pressurelPressure Gradient - change in pressure over distance Wide or dashed is weak Close spacing is stronglRule of Thumb but not alwa

7、ys: High pressure - descending air / good wx Low pressure - ascending 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. l Earth Spins on Axis (1 revolution in 24 hours):l

8、 Poles rotate in space.l At same time, a spot on equator travels 25,000 miles (1040 miles per hour).l If 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.l While the ball is on its way, the Earth continues to rotate.l By the time

9、 the ball gets to where we threw it, the earth has moved.l Because the earth moved out from under the ball, the ball lands in the ocean. Not in China. l If we look at the path the ball took across the ground, it will have curved to the right l 1. in the northern hemisphere, the geostrophic wind is p

10、arallel to the isobars with the lowest pressure on the left.l 2. the closer together the isobars, the stronger the pressure gradient/geostrophic wind speed. l 3. In the Northern Hemisphere, winds tend to blow counterclockwise around low pressure centers and clockwise around high.l 4. geostrophic bal

11、ance does not occur in small scale circulations such as sea breezes, thunderstorms, tornadoes, and dust devils because pressure gradient force is greater here than coriolis. l 1. winds increase with altitude in the atmospheric boundary layer, with the greatest increases just above the surface.l 2. t

12、he wind changes direction clockwise (veers) with increasing altitude.l 3. when winds near the surface are strong, the boundary 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 bound

13、ary 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. when 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

14、 of anticyclones. lStrong accelerations and vertical development can produce quick and large pressure gradients. Examples include wind accelerating over hills, and down drafts from rain. Convection Orographic Convergence/Divergence Frontal Based upon the difference between the adiabatic lapse rate o

15、f 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 tumble lBased upon lapse rateslStandard: 2C per 1000lDry: 3C per 1000lMoist: 1.2C 2.8C per 1000lAdiabatic Cooling/warming:lChange in temperature due to a change

16、in pressure lAs air rises, it expands and cools. Adiabatic coolinglLapse rates DALR - 3 C/ 1000 SALR - Variable If lower than ambient, then unstable Standard Lapse Rate - 2C/1000lTemp inversion occurs in stable air lEvaporation - heat is added to water, changing it to a gaslSublimation - ice directl

17、y to water vaporlCondensation - air becomes saturated, and water vapor in air becomes liquidlDeposition - water vapor freezes directly to ice lAmount of water vapor air can hold decreases with air temperature.lDewpoint temperature is full saturationlFrost Dewpoint is below freezing, and the surface

18、is below dewpoint Water vapor deposition lLatent heat of evaporation Heat to vaporize 1 gram of water (540 cal)lLatent heat of condensation Water vapor gives back heat Violent energy is released when thousands of tons of moisture condense into a thunderstorm cloud Latent Heat and Stability When air

19、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 adiabatically the stability can be changed due to this latent heat. Adibitaic cooling can be somewhat offest from latent heat. Re

20、vision 1 .0 Formation 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 be water vapor, condensation nuclei) Air is cooled to its dew point. (through adiabatic expansion or cold sur

21、face 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 on populates near cities. Sierra Academy of AeronauticsInternational Training Center Private Pilot Gro

22、und Course Revision 1 .0 Fog: Steam Fog Upslope Fog Precipitation Fog Advection Fog Radiation Fog Sierra Academy of AeronauticsInternational Training Center Private Pilot Ground Course Revision 1 .0 Steam Fog: Very cold, dry air moves over warmer water. Air near water surface picks up moisture due t

23、o evaporation and heat. This warmer, moist air rises, cools, and reaches its dewpoint. Sierra Academy of AeronauticsInternational Training Center Private Pilot Ground Course Revision 1 .0 Upslope Fog: Warm, moist air is pushed up sloping terrain by wind. Air cools adiabatically to dewpoint. Sierra A

24、cademy of AeronauticsInternational Training Center Private Pilot Ground Course Revision 1 .0 Precipitation Fog: Warm rain falls through cold air. Air picks up moisture from evaporation and quickly reaches its saturation point. Sierra Academy of AeronauticsInternational Training Center Private Pilot

25、Ground Course Revision 1 .0 Advection 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 AeronauticsInternational Training Center Private Pilot Ground Course Revision 1

26、 .0 Radiation Fog: Moist air is heated during day. Nighttime terrestrial radiation cools earth and nearby calm air to dewpoint. Valley Fog Ground Fog Ice Fog Sierra Academy of AeronauticsInternational Training Center Private Pilot Ground Course Revision 1 .0 Valley Fog: Air is moist due to rivers or

27、 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 above the earths surface of the lowes

28、t 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 behavior lFour Groups or Families Low (surface to 6500AGL) M

29、iddle (6500 to 20,000AGL - alto) High (above 20,000AGL) Extensive Vertical DevelopmentlNames Cumulus Stratus Nimbus Cirrus lDrizzlelRain/rain showerslSnow/snow showers/snow grainslIce pelletslHail l Just because there is %100 saturation doesnt mean there will be precipitation, most clouds dont preci

30、pitate.l 1. 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.l 2. Most of the time, processes that produce small cloud particles are not very effective in producing large precipitation particles.l 3. Efficien

31、t precipitation producing processes mainly occur in certain cloud types (usually Nimbostratus and cumulonimbus .l Two processes by which precipitation forms- condensation/deposition and collision/coalescence. lWater droplets that have coalesced!lVirga Low relative humidity Evaporates before contact

32、with groundlSupercooled water Remains liquid though cooled freezing Turns to ice or freezing rain lBoundary between air masseslFrontal passage changes: Temperature Wind direction Wind speedlFactors affecting intensity: 1) moisture 2) stability of lifted air 3) speed 4) slope 5) moisture & temp varia

33、tions 6)surface over which it moves lCold, dense, stable air moves into an area of warm, lighter, unstable air.lForces less dense, warm air up.lFast moving steep slope due to frictionlSlow moving leading edge much shallower fair weather cumulus behind lWarm air moves over cooler air at the surface.l

34、Slower moving than cold fronts.lClouds determined by stability and moisture content. If warm, moist, stable: stratus and steady rain If warm, moist, unstable (lifted): cumulus and showery rain lStationary Opposing forces of 2 air masses balance each otherlOccluded Fast moving cold front catches up t

35、o a slow moving warm front Weather dependent on temperature differences lStages (Fig 9-23 and 9-24) Pre-Development Incipient Occluded DissipatinglExtended over a period of days. lTropopause height is about 37,000.lTo 66,000 the temp is -57C in standard atmosphere.lJet Stream Speed range between 60 and 240 knots Occur at breaks in the tropopauselSummer - north and weakerlWinter - south and stronger