Chapter 5. Air Pollution Meteorology

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Chapter 5. Air Pollution Meteorology

• Selami DEMIR
• Asst. Prof.

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Outline

• Introduction
• Solar Radiation
• Atmospheric Pressure
• Lapse rate Potential Temperature
• Atmospheric Stability
• Coriolis Force Gravitational Force
• Pressure Gradient Force
• Overall Atmospheric Motion
• Equations of Motion
• Wind Speed Profile

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Introduction (1/2)

• Air pollutant cycle
• Emission
• Transport, diffusion, and transformation
• Deposition
• Re-insertion
• In large urban areas, there are several
  concentrated pollutant sources
• All sources contribute to pollution at any
  specific site
• Determined by mainly meteorological conditions
• Dispersion patterns must be established
• Need for mathematical models and meteorological
  input data for models

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Introduction (2/2)

• Three dominant dispersion mechanisms
• General mean air motion that transport pollutants
  downwind
• Turbulent velocity fluctuations that disperse
  pollutants in all directions
• Diffusion due to concentration gradients
• This chapter is devoted to meteorological
  fundamentals for air pollution modelling

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Solar Radiation (1/6)

• Solar constant ? 8.16 J/cm2.min
• 0.4-0.8 µ ? visible range, maximum intensity

Ref http//www.globalwarmingart.com/images/4/4c/S
olar_Spectrum.png
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Solar Radiation (2/6)

• Distribution of solar energy on earth

Ref OpenLearn Web Site,
http//openlearn.open.ac.uk/file.php/1697/t206b1c0
1f26.jpg
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Solar Radiation (3/6)

• At right angle on June, 21 ? Tropic of cancer
• At right angle on December, 21 ? Tropic of
  capricorn
• At right angle on March, 21 and september, 21 ?
  Equator

http//upload.wikimedia.org/wikipedia/commons/8/84
/Earth-lighting-equinox_EN.png
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Solar Radiation (4/6)

• Example What is the Suns angle over Istanbul on
  June, 21? Note that Istanbul is located on 40 N
  latitude.
• Solution Sunlight reaches Tropic of Cancer (23
  27') at right angle on June, 21.
• Where
• ? Suns angle at the given latitude
• L2 Latitude of given region
• L1 Latitude of region where sunlight reaches
  surface at right angle

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Solar Radiation (5/6)

• Example What is the Suns angle over a city
  located on 39 N latitude when the sunlight
  reaches surface at right angle on 21 S latitude?
  
• Solution

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Solar Radiation (6/6)

• Homework (due 18.04.2008)
• Make a brief research on Stefan-Boltzman Law and
  write a one page report for your research.
• Comment on what would happen if earths
  inclination were 24 instead of 2327'.
• What determines the seasons? Why some regions of
  earth get warmer than other regions.
• Calculate the sunlight angle over Istanbul
• on March, 21
• on June, 21
• on September, 21
• on December, 21

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Atmospheric Pressure (1/4)

• Force on earth surface due to the weight of the
  atmosphere
• Defined as force exerted per unit surface area
• Units of measurement ? Pascal (Pa), atmospheric
  pressure unit (apu, atm), newtons per
  meter-squared (N/m2), water column (m H2O), etc.
• 1 atm 101325 Pa
• 1 atm 10.33 m H2O
• 1 atm 760 mm Hg
• 1 Pa 1 N/m2
• Atmospheric pressure at sea level is 1 atm

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Atmospheric Pressure (2/4)

• Consider a stationary air parcel as shown
• Force balance (assuming no horizontal pressure
  gradient)

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Atmospheric Pressure (3/4)

• Integrating from h z0 to h z produces

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Atmospheric Pressure (4/4)

• Homework (due 18.04.2008)
• Make a research about pressure measurement
  devices and prepare a one-page report for your
  research. Give brief explanations for each type.
• Calculate the atmospheric pressure on top of
  Everest if it is 1013 mb at sea level.

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Lapse Rate Potential Temperature (1/5)

• Adiabatic ? no heat exchange with surroundings
• Consider an air parcel moving upward so rapidly
  that it experiences no heat exchange with
  surrounding atmosphere
• Enthalpy change
• where
• H1 initial enthalpy of air parcel
• H2 final enthalpy of air parcel
• U1 initial internal energy
• U2 final internal energy
• V1 initial volume
• V2 final volume

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Lapse Rate Potential Temperature (2/5)

• By enthalpys definition
• In infinitesimal expression
• Internal energy substitution
• By internal energy definition

• Enthalpy change is a function of only temperature
  when pressure is constant
• Substituting differential pressure as follows
• Since the process is adiabatic, no heat exchange
  occurs

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Lapse Rate Potential Temperature (3/5)

• This approximation assumed there is no phase
  change in the air parcel
• called Dry Adiabatic Lapse Rate (DALR)
• If any phase change takes place during the
  motion, the temperature change will be far more
  different from DALR
• Called Saturated (Wet) Adiabatic Lapse Rate
  (SALR, WALR)
• Variable, must be calculated for each case
• Also significant in some cases this course does
  not focus on it
• For standardization purposes, Standard Lapse Rate
  (SLR), also known as Normal Lapse Rate (NLR), has
  been defined
• On average, in middle latitude, temperature
  changes from 1C to -56.7C
• SLR -0.66C/100 m

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Lapse Rate Potential Temperature (4/5)

• Lapse rate measurements are taken by a device
  called Radiosonde
• Results of measurements are plotted to obtain
  Environmental Lapse Rate (ELR)
• ELR is real atmospheric lapse rate
• Another significant concept is Potential
  Temperature
• Defined as possible ground level temperature of
  an air parcel at a given altitude

where ? Tp potential temperature of air
parcel T Temperature of air parcel H Height
of air parcel from ground DALR Dry adiabatic
lapse rate
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Lapse Rate Potential Temperature (5/5)

• Homework (due 18.04.2008)
• Calculate potential temperature for given data
• Calculate the atmospheric temperature at 800 m
  from the ground if the atmosphere shows adiabatic
  characteristic and the ground level temperature
  is 12C.

Height, m Temperature, C
350 8
750 2
1200 14
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Atmospheric Stability (1/8)

• If ELR lt DALR Then
• Superadiabatic meaning unstable
• ElseIf ELR DALR Then
• Neutral
• ElseIf DALR lt ELR lt 0 Then
• Subadiabatic meaning stable (weakly stable)
• ElseIf DALR lt 0 lt ELR Then
• Inversion meaning strongly stable
• EndIf

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Atmospheric Stability (2/8)

• Superadiabatic

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Atmospheric Stability (3/8)

• Neutral

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Atmospheric Stability (4/8)

• Subadiabatic

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Atmospheric Stability (5/8)

• Inversion

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Atmospheric Stability (6/8)

• If d?/dz lt 0 Then
• Superadiabatic
• ElseIf d?/dz 0 Then
• Neutral
• ElseIf d?/dz gt 0 Then
• Subadiabatic
• EndIf

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Atmospheric Stability (7/8)

• Example Calculate vertical temperature gradient
  and comment on atmospheric stability condition if
  the atmospheric temperature at 835 m is 12 C
  when the ground temperature is 25 C.
• Solution
• The atmosphere is said to be unstable since ELR lt
  DALR

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Atmospheric Stability (8/8)

• Homework (due 25.04.2008)
• Following measurements are taken over Istanbul at
  different times. Determine atmospheric stability
  condition for each case.
• Briefly explain stable air, unstable air, neutral
  air and inversion.
• Make a brief research about the role of
  atmospheric stability in dispersion of pollutants
  in the atmosphere and prepare a-one-page report
  for your research.
• What is conditional stability? Explain.

Height, m Temperature, C Temperature, C Temperature, C Temperature, C
Height, m Case 1 Case 2 Case 3 Case 4
0 14 22 17 4
1000 8 8 7 6
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Coriolis Force

• The Coriolis effect is an apparent deflection of
  moving objects from a straight path when they are
  viewed from a rotating frame of reference.
  Coriolis effect is caused by the Coriolis force,
  which appears in the equation of motion of an
  object in a rotating frame of reference.
  (Wikipedia Web Site, http//en.wikipedia.org/wiki/
  Coriolis_Force)

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Gravitational Force (1/3)

• The force exerted by the earth on an object in
  earths attraction range
• Caused by attraction forces between two masses
• m1 being the mass of earth (M) and m2 is that of
  an object near earth surface

FA attraction force ? 6.66810-11
Nm2/kg2 m1,m2 objects masses r distance bw
masses
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Gravitational Force (2/3)

• Example Determine the acceleration of an object
  near the Eraths surface due to gravitational
  attraction force
• Solution

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Gravitational Force (3/3)

• Homework (due 25.04.2008)
• Determine the acceleration of an object near the
  Martian surface due to gravitational attraction
  force
• Determine the acceleration of an object near the
  Moons surface due to gravitational attraction
  force

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Pressure Gradient Force

• Consider an air parcel accelerating in a
  horizontal direction
• In three dimensional representation,

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Overall Atmospheric Motion (1/7)

• Consider an air parsel accelerating around the
  Earth
• Overall acceleration

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Overall Atmospheric Motion (2/7)

• Neglecting vertical terms and re-arranging, we get

u velocity of atmospheric motion in east-west
direction v velocity of atmospheric motion in
north-south direction O rotational speed of
earth 7.2910-5 r/s F latitude on which the
motion occurs
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Overall Atmospheric Motion (3/7)

• Example Briefly explain the mechanisms that
  forced radioactive pollutants towards Turkeys
  coasts after Chernobyl. Tell about the
  meteorological conditions then. Show the pressure
  centers and wind patterns on the day of accident
  and two day after the accident on a brief map.
  Consider the aspects of geostrophic winds.

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Overall Atmospheric Motion (4/7)

• Solution

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Overall Atmospheric Motion (5/7)

• Example Isobars are shown in the figure below,
  for 40 latitude in the Northern Hemisphere, at
  an altitude of 5600 meters. Determine the
  geostrophic wind speed in km/hour
• Temperature at 5600 m -28C
• Coriolis force 2 ? V sin ß
• ? 7.3 x 10-5 radians/s ß Latitude degrees
  V geostrophic wind speed
• 1 mb 100 N/m3

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Overall Atmospheric Motion (6/7)

• ExampleSuppose a nuclear accident occurs at a
  place of 3,000 km west of Istanbul. Radioactive
  pollutants are pumped above the planetary
  boundary layer (PBL) with the power of explosion.
  On the day of nuclear accident, the radiosonde
  data taken at different places of Europe shows
  that atmospheric pressure is decreasing towards
  north at a rate of 0.0015 N/m3 and this pattern
  is valid for the whole Europe. Will the
  radioactivity affect Istanbul? If yes, when? Note
  that Istanbul is located on 40 northern latitude
  and worlds angular speed of rotation is 7.3
  10-5 radians/sec. You may assume the density of
  air at the level where geostrophic wind equations
  apply as 0.70 kg/m3.

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Overall Atmospheric Motion (7/7)

• Solution

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Equations of Motion (1/3)

• Eularian Approach
• The observer stays stationary and observes the
  change in the value of a function f
  (concentration, atmospheric parameters, etc.)
• The coordinate system (reference frame) is
  stationary
• The objective is moving
• Lagregian Approach
• The observer moves with the moving objective and
  observes the change in the value of a function f
• The coordinate system is moving with the
  objective at the same speed and direction

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Equations of Motion (2/3)

• Lagregian Approach (contd)

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Equations of Motion (3/3)

• Examples will be given later

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Wind Speed Profile (1/2)

• Due to friction near surface, wind speed
  increases with height exponentially
• Wind speed is measured by a device called
  anemometer
• 10 m should be chosen for anemometer height

Stability Class P
A 0.15
B 0.15
C 0.20
D 0.25
E 0.40
F 0.60
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Wind Speed Profile (2/2)

• Homework (due 25.08.2008)
• Calculate wind speeds for Class B stability at
  20, 30, 50, 100, 200, and 500 m if it is 1.2
  m/sec. Plot the results.
• Comment on how the wind speed would change with
  altitude if the stability class were Class E.