Chapter 7: Transient Atmospheric Flows and Disturbances

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Chapter 7 Transient Atmospheric Flows and
Disturbances
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Outline

• Impact of air masses on landscape
• Air masses
• Fronts
• Atmospheric Disturbances

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Impact of Air masses

• Storms temporary and transient
• Wind and Pressure system have a broad based
  impact on climate
• Short-term and long-term impacts on vegetation,
  climate, ecosystem diversity
• Landscape also impacts airflow

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Air masses
Distinct parcels of air must be - large,
often1000 miles in diameter and several miles
thick in troposphere - relatively homogeneous
(horizontally)at a given altitude and latitude
(temperature, RH and stability). it can modify
as it travels Source regions
origin - stable, stationary anticyclonic
areas - oceans and flat continental regions
(away from jet streams) are best -Sourcee
regions determines properties Warm air masses
Southern North Atlantic, Southern North Pacific,
Gulf of Mexico Cold air masses Northern Atlantic
and Pacific, Northern and Central Canada
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Air masses contd
In general, six types - Arctic/Antarctic
A - continental polar cP - maritime polar
mP - continental tropical cT - maritime
tropical mT - equatorial E Air masses are
distinctive - temperature, moisture and
pressure characteristics An air mass
modifies as it moves (in terms of temp, pressure
and moisture)
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Fronts Boundaries between air masses (temperature
main factor) Characteristics width, length,
height, movement   Generally between warm and
cold air   Warm front advancing warm air, slopes
1200 as rises above surface, stratus clouds,
light (occasionally heavy) steady
precipitation   Cold front advancing cold air,
slopes 1100, move faster than warm fronts,
rapid lifting, cumulus clouds, heavy showery
precipitation, occasional violent
weather  Stationary front common boundary in
which neither air mass displaces the
other    Occluded front cold front overtakes a
warm front, cold air at surface, warm air above
this, cool air above warm
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Warm Fronts
Figure 7-9
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Cold Fronts
Figure 7-12
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Weather map symbols
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Atmospheric Disturbances Two Types Stormy and
Calm. Variable migratory and brief Both have
common Characteristics small and variable,
migratory and transient, brief, predictable
pattern Midlatitude cyclones Large migratory,
low pressure systems, Westerlies, Lows, wave
cyclones, depressions, Brings precipitation, day
to day weather is affected, most significant of
all disturbances Mature is 1000 miles in dia,
oval, N and S mirror of each other Counterclockwis
e in North. Cool in North and west and warm in
south and west Cool clear, cold stable Warm
cloudiness and precipitation 3-6 days for
maturity and 3-6 days for dissipation Bring heavy
rain to North Eastern US Westerlies and are
erratic
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Midlatitude anticyclones Extensive migratory
high pressure cells Larger than cyclones West to
east Cyclones and anticyclone alternate with one
another in regular sequence Stagnant Often
functional relation between the two Major
Tropical DisturbancesCyclones Outside of
3Degrees Hurricanes (North America), typhoons (
Western North Pacefic), Baguios ( Philippines)
and tropical cyclones ( Indian Oceans and
Australia) Eye wall (10-25 mile), eye wall
replacement, Predictable, lasts for a week,
Damage and destruction
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Minor atmospheric disturbances Easterly Wave
Long, weak, migratory Low pressure system ,
5-30 lat, drifts westwards, fair weather
ahead, clear weather follows Thunderstorm
Violent convective storms, lightening, localized
and short lived Tornados deep low pressure
cell surrounded by whirling cylindrical
wind, localized, ¼ mile in diameter, most
extreme pressure gradient, in summer and
spring, 90 in US, contact between cp and mT
masses
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Hurricanes
Figure 7-24
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Hurricane Locations
Figure 7-25
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Thunderstorms
Figure 7-30
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Distribution of Tornadoes
Figure 7-36
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GOES Geostationary operational Environmental
Satellite Useful for weather forecasting Geostati
onary at 22,300 miles Two one above equator in S
America and Other is above equator in Pacific (75
W and 135 W) Sounder Gives temperature and
moisture info Imager detects radiation and
electromagnetic wave
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Oklahoma Storms NEXRAD uses Doppler effect
change in sound and electromagnetic waves as
source is moving Vertical wind profiler examines
wind condition using Doppler radar Microwaves
transmitted through atmosphere More precise than
radar Dryline between T and cT Mesonetwork 111
solar powered weather stations updated every 15
minutes
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Extratropical cyclones (lows) Characteristics
(generalized) - 1000 mile diameter - low
pressure - stormy weather in vicinity of
low - counter clockwise circulation in
N. Hemisphere - circulation results in
leading warm front and trailing cold front
Movement - generally west to east - 20-30
MPH (crosses US in 3-4 days)