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Chapter 5. Air Pollution Meteorology

- Selami DEMIR
- Asst. Prof.

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

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

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

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

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

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

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

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

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

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

Atmospheric Pressure (2/4)

- Consider a stationary air parcel as shown
- Force balance (assuming no horizontal pressure

gradient)

Atmospheric Pressure (3/4)

- Integrating from h z0 to h z produces

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.

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

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

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

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

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

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

Atmospheric Stability (2/8)

- Superadiabatic

Atmospheric Stability (3/8)

- Neutral

Atmospheric Stability (4/8)

- Subadiabatic

Atmospheric Stability (5/8)

- Inversion

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

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

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

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)

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

Gravitational Force (2/3)

- Example Determine the acceleration of an object

near the Eraths surface due to gravitational

attraction force - Solution

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

Pressure Gradient Force

- Consider an air parcel accelerating in a

horizontal direction - In three dimensional representation,

Overall Atmospheric Motion (1/7)

- Consider an air parsel accelerating around the

Earth - Overall acceleration

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

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.

Overall Atmospheric Motion (4/7)

- Solution

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

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.

Overall Atmospheric Motion (7/7)

- Solution

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

Equations of Motion (2/3)

- Lagregian Approach (contd)

Equations of Motion (3/3)

- Examples will be given later

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

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.