Transcript Module-3-Part-2-Air-Env-

Air Environment
Module 3
Aviation Weather
Ted Spitzmiller
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WEATHER SYSTEMS
1.
2.
3.
4.
Air Circulation
Weather Elements
Moisture & Clouds
Weather Systems & Changes
Significance of italics—immediate recall
Location in your book (x)
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Source of Weather
• Sun heats the earth by radiation (1)
35 % scattered or
reflected
Sun
15%
absorbed
by
atmosphere
50% absorbed by the Earth
Earth
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Earth’s Seasons Varies Circulation (3)
•
Earth’s Axis tilted 23.5 degrees
rays
•
Sun
rays
Seasons dependent on
– (Spring/Summer/Fall/Winter)
•
Days and nights of equal length on spring and fall equinox
•
Mean distance from Earth to Sun. 149,597,870,691 km or 92.956×10^6 mi
(93 million miles)
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Weather
Elements
(9)
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•
•
•
Wind
Temperature
Pressure
Moisture
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Atmospheric Pressure (13)
• Weight of air (gravity) @ sea level
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–
–
–
14.7 lbs\sq
29.92 inches mercury (hg)
761 mm
1013.2 mb
• Barometer is used to measure air pressure (13)
• Varies with altitude of reporting station —
corrected to SL
• Aneroid barograph provides a permanent
recording of pressure (13)
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Types of Pressure Systems
• Low < 29.92”
generally poor WX
air cools as it rises
(as a bowl fills up)
• High > 29.92”
generally good WX
descending and
warming
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• Pressure gradients
• Local wind systems
Wind
– Land and sea breezes
– Mountain breezes
• The Beaufort Scale can be used on land or sea and is
used for estimating wind velocity (10)
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Beaufort
Scale
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High Pressure Pattern
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29.92 = 1013.2
10
Low Pressure Pattern
29.92 = 1013.2
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Atmospheric Circulation Around
Pressure Systems
• Earths rotation
– Equatorial 1000 mph, poles 0 mph
• Coriolis and surface friction
effect deflects air to right
(record)
– An object in northern hemisphere
is deflected to the right by coriolis
force
• Cyclonic vs anti—cyclonic
(counter—clockwise and
clockwise)
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Pressure Variations
• Trough — elongated low extending from
central low
• Ridge — elongated high usually extending
from central high
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Temperature (12)
• Heat is the total energy of all molecules within a
substance (12)
– Water boils at 212° F (100 C °) and freezes at 32° F (0 ° C)(12)
– Absolute zero 459 degrees F, or -273 C, or 0 Kelvin
• Standard 59 degrees @ sea level (15 C) @ 29.92” hg
F = (1.8 x C) +32
C = (F/1.8 ) – 32
F = 9/5 C +32 What is the equiv of 15° C
•
9 * 15 = 135 = 27 + 32 = 59°
5 1
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STD lapse rate
– 3½ degrees F per 1000 feet (unsaturated air) (2 ° C)
• Temp and wind produce a wind chill factor (10)
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Moisture and Clouds 3 (19)
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•
•
•
•
•
Condensation
Dew point
Fog
Precipitation
Saturation
Relative humidity
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Moisture – Humidity (19)
• Relative humidity — % capable of holding
(example...)
– Air holding all the moisture it can is said to be
saturated (19)
• Dew point — temp @ given pressure air
must be cooled to become saturated (19)
• Example… bathroom shower
• Saturation affects stability of air
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Clouds (20)
• Visible moisture condensed on dust
– Hygroscopic nucleii
• Classifications
– Stratiform — cool, dry, stable, smooth, poor
visibility, drizzle
– Cumuliform — moist, warm, unstable,
turbulent, good visibility, rain
– Cirrus—very high thin wispy clouds
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Weather Systems and Changes 4 (27)
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•
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•
•
air mass
front
hurricane
thunderstorm
tornado
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(27)
Air Mass Characteristics - Temp Pressure Moisture
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Atmospheric Stability
• Air tends to flow horizontally
• May be displaced — lifted
– Terrain
– Thermals
– Air mass differences
• Lapse rate and saturation determines stability
– unsaturated = normally stable
– saturated and cool = normally stable
– saturated and warm = normally unstable
• Stable air resists displacement
• Unstable air readily moves vertically
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Frontal characteristics
• Cold — fast/slow, cumulus,
good visibility
• Warm — slow, status, poor
visibility
• Stationary
• Occluded
• Frontal passage — wind
shift
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Cold Front (28)
Cumulus clouds, local heavy rain, good visibility
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Warm Front
Stratified clouds, steady rain, low visibility
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Cumulus
Moisture
Stratus
Heavy Localized Rain Light to moderate Wide Spread
Visibility
Good
Turbulence Yes
Poor
No
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Cirro-Stratus
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Thunderstorms (29)
• Air mass & frontal
• Requirements
– Lifting
– Moisture
– Unstable air
• Stages (29)
– Cumulus – building
– Mature
– Dissipation
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Tornados (30)
Precautions (31)
• GO to a basement
• Stay away from
windows
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Mountain Waves
• Lenticular
• Lee side turbulence
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Jetstream
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Icing
• Rime
• clear
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Turbulence
• Light
• Moderate
• Severe
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F, MPH, mbars
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Charting you own weather
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