Download Inversions in the Air

Temperature Inversions in Alaska
ITEP Air Quality Training
Kodiak 2015
Barbara Trost/Bob Morgan
Alaska Department of Environmental Conservation
The Atmosphere as seen by Alan Shepard
May 5, 1961 – US 1st Manned Space Flight
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Lavers of the Atmosphere as seen from Space
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Temperature in the Atmosphere
Temperature in the Atmosphere
11000
10000
9000
8000
Alitude in Feet
7000
6000
5000
4000
3000
2000
1000
0
0
10
20
30
40
50
60
70
Temperature in ° F
Dry Air
Moist Air
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Normal Circulation in the Atmosphere in the
Daylight

Warm air rises | cold air sinks
 Temperature decreases as you go higher in
atmosphere
 Warmer near ground, colder aloft
 Mixing between air at low and high levels
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Winter Day, with Good Mixing in the Atmosphere
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Temperature Inversion



After sunset, ground loses heat quickly

Air above ground stays warmer

Colder air at surface is trapped under warmer layer
Temperature profile of atmosphere is inverted

A barrier is formed between the lower cold air and
the upper warm air

Trapping pollution close to ground level
Inversion dissipates after sun heats up ground & wind
mixes air between ground and above surface
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Temperature Inversions (cont.)

Occurs in early morning hours after earth has
lost all heat from sun

Calm winds, clear skies

Cold air will sink into the lowest points, such as
basins or valleys or frozen rivers beds

Cold air can flow down off of hillsides
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Temperature in the Atmosphere with a
Temperature Inversion
Temperature in the Atmosphere
with an Inversion
1200
1000
Alitude in Feet
800
600
400
200
0
0
10
20
30
40
50
60
Temperature ° F
Dry Air
Moist Air
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Winter Day in Fairbanks with a Strong
Temperature Inversion (View from the Hillside)
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Winter Day in Fairbanks with a Strong
Temperature Inversion (View from Ground
Level)
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Seasonal Factors

Occur year-round, but strongest in winter
 Alaska experiences extreme winter inversions
compared to lower 48
 Can be very shallow - ~20 feet
 Temperature difference of 20° over 100 feet of
elevation
Stack is above inversion
inversion
Stack is below inversion
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Health Impacts

Can impact public health

Steam/smoke from smokestack rises and flattens out,
trapping pollution in shallow layer above surface

Traps other pollutants, such as Carbon monoxide
from vehicle exhaust or particulate matter from
residential wood burning

Very cold air makes it difficult to breathe

Ice fog
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