air pollution meteorology ii_020210
TRANSCRIPT
Air Pollution Meteorology
Community Air Pollution
EHS 582
Dvonch
Air Quality in the News
Research on Global 'Sun Block' Needed Now, Experts ArgueScienceDaily (Jan. 28, 2010)
Internationally coordinated research and field-testing on 'geoengineering' the planet's atmosphere to
limit risk of climate change should begin soon along with building international governance of the
technology, say scientists from the University of Calgary and the United States. Solar-radiation
management (SRM) would involve releasing megatonnes of light-scattering aerosol particles in the
upper atmosphere to reduce Earth's absorption of solar energy, thereby cooling the planet. Another
technique would be to release particles of sea salt to make low-altitude clouds reflect more solar energy technique would be to release particles of sea salt to make low-altitude clouds reflect more solar energy
back into space…. Long-established estimates show that SRM could offset this century's predicted
global average temperature rise more than 100 times more cheaply than achieving the same cooling by
cutting emissions…
SRM would also cool the planet quickly, whereas even a massive program of carbon dioxide emission
cuts will take many decades to slow global warming because the CO2 already accumulated in the
atmosphere will take many years to naturally break down. The 1991 eruption of Mount Pinatubo, for
example, cooled the planet by about 0.5 degrees Celsius in less than a year by injecting sulphur into the
stratosphere. But a world cooled by managing sunlight will present risks, the scientists note. The planet
would have less precipitation and less evaporation, and monsoon rains and winds might be weakened.
Some areas would be more protected from temperature changes than others, creating local 'winners' and
losers.‘ "If the world relies solely on SRM to limit (global) warming, these problems will eventually
pose risks as large as those from uncontrolled emissions,“…
Differential Heatingof Earth
Incident Solar Radiation
January
July
(Courtesy of NASA)
Earth Albedo
Albedo =Reflected Solar Radiation
Incoming Solar Radiation
Annual Global Average Albedo = 30 %
Fresh Snow = 90 % Plowed Field = 15 % Water = 10 % (Small )zenithθ
Energy Balance
Energy Balance as Function of Time of Day
Global Surface Temperatures
Air Pollution Meteorology
Important Terms
• Inversion
• Wind speed & • Wind speed &
direction
– stagnation
• Stability
• Vertical motion
Convection
Planetary Boundary Layer
…is that part of the atmosphere that is directly impacted by
the Earth’s surface
– 300 to 3000 meters in depth
Planetary Boundary Layer
Atmospheric Stability (Dry Processes)
Z
Environmental Lapse Rate
• If the atmosphere cools at a
rate less than the DALR, the
atmosphere is STABLE andZ
T
Dry Adiabatic LR
atmosphere is STABLE and
will suppress the parcel motion.
Atmospheric Stability (Dry Processes)
Z
Environmental Lapse Rate
• If the atmosphere cools at the same
rate as the DALR, the atmosphere
is NEUTRAL and will have noZ
T
Dry Adiabatic LR
is NEUTRAL and will have no
impact on the parcel motion.
Atmospheric Stability (Dry Processes)
Z
• If the atmosphere cools at a
rate greater than the DALR, the
atmosphere is UNSTABLE and
parcel will continue to move until
it reaches a level where the atmosphereZ
T
Dry Adiabatic LR
Environmental Lapse Rate
it reaches a level where the atmosphere
is warmer than the parcel itself.
EHS 582 Community Air Pollution
Stability in Saturated Air
1.6
1.8
2
2.2
ΓΓ
Absolutely
stable
Absolutely
unstable
Conditionally
unstabled w
Alt
itude
(km
)
0.8
1
1.2
1.4
1.6
-2 0 2 4 6 8 10 12 14Temperature (
oC)
stableunstable
1 4
32
Alt
itude
(km
)
Stability in Multiple Layers
2
2.5
3A
ltit
ude
(km
)
Conditionally unstable
Saturated neutral
Saturated neutral
0
0.5
1
1.5
0 5 10 15 20 25
Alt
itude
(km
)
Temperature (oC)
Γe
Γd
Γw
Absolutely unstable
Absolutely stable
Unsaturated neutral
Conditionally unstable
Environmental Lapse Ratechange air temperature with altitude
Γe = −∆T
∆z= −
T zhi( )− T zlo( )zhi − zlo
Γe = −20o C −15oC
2 km − 1 km= −
5o C
km
Γe = −15o C − 21oC
1 km − 0 km= +
6o C
km
Temperature Inversion
1.5
2A
ltit
ude
Alt
itude
(km
)
Top temp.
0
0.5
1
10 12 14 16 18 20 22
Alt
itude
Temperature (oC)
Alt
itude
(km
)
Strength
Top h
eight
Thick
ness
Bas
e hei
ght
Top temp.
Base temp.
Types of Inversions
Large-Scale Subsidence Inversion Radiation Inversion
H
warm radiated air
cool marine air
warm air from subsidence
land
sea
land
surface air cooled
Rising smoke forms a ceiling over the valley due to an inversion
Trapping Pollutants Under an Inversion
1.5
2
2.5
3
Alt
itude
(km
)
0
0.5
1
1.5
0 5 10 15 20 25 30Temperature (
oC)
Γe
Alt
itude
(km
)
Figure 6.11
AM and PMTemperature Profiles
500
600
700
260270280290300310320
Morgan Hill
8/06/90
15:30 PST
Pre
ssure
(m
b)
260 270 280 290 300 310 320
700
800
900
1000
Temperature (K)
15:30 PST
03:30 PST
Pre
ssure
(m
b)
Impact of Changing Mixing DepthLos Angeles, Dec. 19, 2000
Mark Z. Jacobson
Noon Late afternoon
The Beach!
H
H
Basic sea-breeze cell
Large-scale sea-breeze cell
LMountain chimney effect: injection of pollutants to free troposphere
Elevated pollution layers
Sea Breeze Circulation
Desert Coast Ocean
(hot) (warm) (cold)
HLL
Basic sea-breeze cell
Elevated Pollution From Sea Breeze
(Los Angeles, July 22, 2000)
M. Z. Jacobson
Sea-Breeze Impact on Pollution
Eagle Harbor
Pellston
Eagle Harbor
Pellston
Grand Rapids
Flint
Dexter
Detroit Detroit
Dexter
Flint
Grand Rapids
Smoke Stack Plumes
• What type of plume behavior did you
observe in the UM Power Plant this AM?
• What factors affect the behavior of this
plume? Other plumes?
-Occurs overnight/early morning
-Result: Long-range transport
-Occurs during the morning as the lower portion
of the boundary layer warms.
-Result: Enhanced deposition close to the source.
-Occurs during the late morning and early
Atmospheric Stability
-Occurs during the late morning and early
afternoon. Pollutants caught in up/downdrafts.
-Result: Deposition close to the surface.
-Occurs during the mid-afternoon or under
cloudy conditions.
-Result: Pollutants spread out fairly evenly.
-Occurs during the early evening as surface
cools and becomes more stable.
-Result: Long range transport with some
vertical dispersion.
Air Pollution Modeling
where:
The "standard" algorithm used in plume studies is the Gaussian Plume Model
of O.G. Sutton(1932) is as follows:
http://www.shodor.org/os411/courses/_master/tools/calculators/gplume/gplumeinfo.html
1. C(x,y,z) is the concentration of the emission (in micrograms per
cubic meter) at any point x meters downwind of the source, y meters
laterally from the centerline of the plume, and z meters above ground
level.
2. Q is the quantity or mass of the emission (in grams) per unit of
time (seconds)
3. u is the wind speed (in meters per second)
4. h is the height of the source above ground level (in meters)
5. σy and σz are the standard deviations of a statistically normal
plume in the lateral and vertical dimensions, respectively
Differential Heatingof Earth
Convection
Current Weather
Coriolis Effect
At the surface air will flow away from an area
of high pressure and move in a clockwise direction.
1012 mb
1016 mb
Similarly, at the surface air will flow toward the center
of lower pressure and move in a counter clockwise manner.
Weather
Cold Frontal Boundary
Colder Air Warmer Air
If the rising air has enough moisture, water vapor will condense
to form clouds and precipitation. This type of precipitation is
generally short-lived, but relative heavy in nature.
Warm Frontal Boundary
Colder AirWarmer Air
If the rising air has enough moisture, the water vapor will
condense to form clouds and precipitation. This precipitation
is typically light and of long duration.
Weather
Weather