Download Inversions and PM 2.5 Meteorology Overview

Joe Solomon
National Weather Service Pendleton
[email protected]
541-276-8134
Nighttime
Temperature
profile of an
Inversion
A Layer of
Warm air
over
Cold air
Inversions
Cold air is
more dense
and heavier
than warm air
Profile of the Atmosphere
-60
-20
20
60
100
140
Temperature normally
decreases
with increasing
altitude in the
troposphere.
140
Temperature
THERMOSPHERE/
IONOSPHERE
100
60
Pressure
60
Mesopause
MESOSPHERE
Stratopause
20
-20
20
60
100
40
Referred to as
Lapse Rate.
STRATOSPHERE
cooling
20
Tropopause
-60
80
TROPOSPHERE
140
02-05-S290
Comparing Lapse Rate & Stability
LAPSE RATE
3.5 degs. / 1000 ft.
(Average)
5.5 degs. / 1000 ft.
(Dry)
Change in Temperature
3.0 degs. / 1000 ft.
(Moist)
Neutral
<5.5 degs. / 1000 ft.
(STABLE)
With Altitude
1,000 ft.
>5.5 degs. / 1000 ft.
(UNSTABLE)
Temperature
04-06-S290
Lapse Rate = rate at which temperature changes with height
1
S-290 Skills…Atmospheric
Stability
Air Stability
Stable Air –
Resists vertical motion
Poor Ventilation/Mixing Height
Unstable Air –
Encourages vertical motion
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Good Ventilation/Mixing Height
A Day in the Life of a
Rising Air Parcel
8.0º
8.0º F
49.0º
49.0º F
8.5º
8.5º F
A Day in the Life of a
Rising Air Parcel
13,000 ft AGL
55.0º
55.0º F 52.5º
52.5º F
5,000 ft AGL
52.5º
52.5º F
A parcel of air will continue to rise
as long as it remains warmer than
the air around it.
74.0º
74.0º F
0 ft AGL
80.0º
80.0º F
bare field
Fields covered with vegetation
06-53-S290-EP
5,000 ft AGL
Once the parcel becomes cooler
than the air around it, it stops
rising. If it becomes cooler than the
air around it, it begins to sink.
74.0º
74.0º F
0 ft AGL
80.0º
80.0º F
bare field
Fields covered with vegetation
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A Day in the Life of a
Rising Air Parcel
If the parcel never becomes warmer
than the air around it, it never rises.
74.0º
74.0º F
73.0º
73.0º F
bare field
0 ft AGL
Fields covered with vegetation
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The skew-T diagram is used to represent the pressure,
temperature, density, moisture, wind and atmospheric
stability within a column of atmosphere above a point on
the earth’s surface.
2
Spokane Morning Sounding
Temperature normally
decreases
with increasing
altitude…
But what is normal when
it comes to weather?
cooling
What is a Temperatures Inversion?
Atmospheric Lapse Rates
An inversion is a layer
of very stable air
where temperature
increases with an
increase in altitude.
Very Stable
15º F/M FT
An inversion acts like
a cap or lid to severely
limit the upward
movement of air.
-3º F/M FT
-5.5º F/M FT
Warmer
Inversions often exist
at many levels of the
troposphere.
Unstable
Stable
Neutral
-15º F/M FT
Temperature
Polar Region
Troposphere
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The
Troposphere
The lowest layer
of the
atmosphere
varies in height
from 9 to 12 miles
above sea level
over the tropics,
to about 6 miles
above sea level
over the polar
regions.
The Tropics
3
The Solar Radiation Budget
Reflected by
earth’s surface: 3%
Reflected by
clouds: 22%
Reflected by
atmosphere: 5%
100%
5%
Direct Sunlight
Heat Loss at Night
Net Radiation to
Space and Atmosphere
Absorbed by
atmosphere
and clouds: 20%
22%
Absorption by
Clouds and Atmosphere
Direct
50%
3%
Reflection
from Clouds
Convection and Conduction
from Air near surface
Condensation
of Dew
Indirect Sunlight
Conduction from Soil
Faster cooling near the surface than aloft
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The Seasons in the Northern Hemisphere
Seasonal
Change
In
Solar
Angle
At 40ºN
Latitude
The Solar Radiation Budget
Angle of Solar Rays
Reflected by
earth’s surface: 3%
Reflected by
clouds: 22%
Reflected by
atmosphere: 5%
100%
5% > 15%
Direct Sunlight
N
Absorbed by
atmosphere
and clouds:
20%
22% > 35%
Direct
S
3% > 10%
50% > 20%
Indirect Sunlight
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02-10-S290
4
(Seasonal) Net Incoming vs.
Net Outgoing Radiation
Incoming Radiation
Outgoing Radiation
Seasonal warmest
Temperature
• The end result…the impact of inversions is
greater during the Winter VS Summer as
Winter inversions can last many days.
Seasonal coldest
Temperature
Amount
of
Heat
Mar
Jun
Sep
Dec
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Nighttime or Radiation Inversion
Four Types of Inversions
Sunset
Strong cold
air drainage
Weak
inversion
Midnight
Weak cold
air drainage
Moderate
Inversion
Sunrise
Little or no
drainage flow
Strong
Inversion
During the evening hours, this surface based inversion is weak and
shallow, usually no more than a few hundred feet deep. As cold air
drainage and radiational cooling continues overnight, this inversion
strengthens and eventually reaches its maximum depth around
sunrise when surface temperatures are at their lowest.
Drainage winds
Summer Nights
Shallow
Inversions
Winter Nights
Deep
Inversions
lower on valley walls and
mountain slopes during
the summer with shorter
nights and less radiational
cooling and cold air
drainage.
higher on winter nights
with stronger radiational
cooling and cold air
drainage. May be
thousands of feet above
the valley floor.
5
Thermal belts tend to form
higher on the walls of
broad valleys and
gently slopes canyons.
Broad Valleys
lower on mountain slopes
and steep canyons with
strong drainage.
Most Effective Way to Destabilize
(Change slope of temperature line ~ increase lapse rate)
5.5 degs. / 1000 ft.
(Dry)
Cooling Aloft (Upper level “disturbance”)
Resulting lapse rate
1,000 ft.
Surface Heating (Sunshine)
Temperature
Evolution of the
Mixing Layer.
Summer
Comparing Lapse Rate & Stability
3.5 degs. / 1000 ft.
(Average)
5.5 degs. / 1000 ft.
(Dry)
12,000 Ft AGL
3.0 degs. / 1000 ft.
(Moist)
Maximum Mixing Height
2 PM
7400 Ft AGL
Neutral
<5.5 degs. / 1000 ft.
(STABLE)
1,000 ft.
2 PM
Noon
Noon
10 AM
10Ft
AM
1500
AGL
>5.5 degs. / 1000 ft.
(UNSTABLE)
2800 FT AGL
58ºF
8 AM
8 AM
Temperature
Lapse Rate = rate at which temperature changes with height
55ºF
63ºF
75ºF
80ºF
88ºF
Evolution of the
Mixing Layer.
Spring or Fall
Maximum Mixing Height
2 PM
10 AM
50ºF
45ºF
53ºF
58ºF
2000 FT AGL
1500
Ft AGL
2 PM
10 AM
Ground
Ground
Evolution of the
Mixing Layer.
Winter
500 Ft AGL
50ºFHeight
Maximum Mixing
45ºF
53ºF
2 PM
2 PM
58ºF
Ground
6
Inversions break as temperatures near the surface increase fasten than aloft.
Common during the Summer, but more difficult to occur during the Winter
due to lack of surface heating.
Inversion form by temperatures cooling near the surface fasten than aloft.
5000’
Height
Dry Adiabat
2000
0500
0200
1830
0
Temperature
Four Types of Inversions
Subsidence
Inversions
Aloft
Subsidence
Subsidence
Inversions
Inversions
Aloft
strongest in late
summer and
autumn, and on
the north and
east sides of
strong high
pressure ridges
that remain over a
region,
sometimes for
weeks at a time.
Lowering Subsidence Inversion
Temperature
Sounding
Subsidence is a slow process that can occur over several
days. During this period, a subsidence inversion will grow
stronger as it lowers and becomes progressively
warmer and drier than the layer of air below it.
Poor ventilation
conditions develop
below a lowering
subsidence inversion.
7
Cold Fronts
Cold Fronts
Fronts with
with
Cold
Wind
Wind
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Frontal Passage
warmer, lighter air
cooler, heavier air
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