Air Pollution Control
Engineering
Prof. Jiakuan Yang
Huazhong University of Science and
Technology
Questions for the Last Lecture
1. Which two meteorological factors have great effect on
air pollution transportation?
2. Which two factors ( or parameters ) affect vertical motion
in the atmosphere ?
3. Which two parameters can describe the temperature change
of the air parcel and the surrounding atmosphere when the air
parcel rise up?
Important meteorology elements on air pollution
wind speed and direction
atmospheric stability
Factors that affect vertical motion
density
temperature
 .
T .T
RH ( Relative Humidity)
P( Pressure)
'
'
  '
a
g
'

T T
a
g
T
'
Other two factors that affect vertical motion
RH ( Relative Humidity)
humidity
RH =
The ratio of the
water content of
the air
saturation humidity
M≈29－0.253RH
ρ= PM / TR
RH
M
ρ
a
Other two factors that affect vertical motion
P( Pressure)
dP
dz
= －ρg
Vertical distance
P
ρ
a
d
s
a

Dry adiabatic lapse rate (
d ) is used to describe
the temperature decrease of an air parcel when the
air parcel rise.
dT
d 

dz
10℃/km
Standard lapse rate (  s ) is used to describe the
temperature decrease of surrounding air (or
atmosphere) when the height increase.
dT
s 
 6.5C / km
dZ
Actual lapse rate(
a
)
Lecture 5
Meteorology for air pollution
control Engineers
Ⅰ Relationship between meteorology and air pollution
Ⅱ Effects of horizontal atmospheric motion on
atmospheric stability
Ⅲ Effects of vertical atmospheric motion on
atmospheric stability
Ⅳ Mixing Height (混合高度) and Fumigation(薰烟扩散)
(4) Standard lapse rate (标准直减率)
Sun light is transparent through the atmosphere, so
the ground absorbs the largest amount of heat.
Commonly the ground temperature is the
highest.
The farther away the ground, the lower temperature.
(4) Standard lapse rate (
s
)
dT
 6.5C / km
dZ
dT
s 
 6.5C / km
dZ
(4) Standard lapse rate (  s )
In the daytime, the nearer the
ground, the higher temperature
of the atmosphere.
Z
1km
23.4°C
Actual lapse rate(
23.4°C
30°
C
T
a )
(5) Atmospheric stability
Questions
T T
a
g
T
'
How do changes of the temperatures
affect the atmospheric stability?
(5) Atmospheric stability
Z(m)
Surrounding air
Polluted air parcel
T ' T
a 
g
T
T '  T0   d Z
T  T0   a Z
0
T(℃)
ag
 a  d
T
Z
(5) Atmospheric stability
ag
Z(m)
 a  d
T
Z
Change of the polluted air parcel is the same.
d 
10℃/km
However, the temperature distribution of the
the surrounding air will change from time to
time, and from one place to another place.
0
T(℃)
d a
( a ) unstable
Z
Z1
Z0
ag
T1
T1’
T0
T
Z
 d   a  Z .a
T2’ T2
0
 a  d
When air parcel rises,
T
T1’ > T1
air parcel will rise upper and upper.
When air parcel falls,
T2’ < T2
air parcel will rise upper and upper.
( b ) neutral
Z
d a
ag
 a  d
T
a=0
0
T
Z
( c ) stable
d a
Z
ag
 a  d
d a
0
T
T
Z
Z a
( d ) very stable
dT
0
dZ
 a  d
ag
Z
T
Z
temperature inversion
dT
0
dZ
0
T
Z a
Temperature inversion
Vertical temperature distribution model at the various time .
Z
Z
300m
0
300m
10°C
( a ) Dawn
T
0
21°C
T
( b ) Dawn + 2h
Temperature inversion
Vertical temperature distribution model at the various time .
Z
Z
1800m
300m
0
27°C T
( c ) Dawn + 4h
0
T
( d ) Midafternoon
平流逆温
暖空气平流到冷地面上而下部降温
而形成
暖空气团
高温
低温
锋面逆温
冷、暖气团相遇
暖气上爬，形成锋面
冷暖间逆温
Ⅳ Mixing Height (混合高度)
Air pollutants released at ground level will be mixed almost
uniformly up to the mixing height , but not above it . Thus
the mixing height sets the upper limit to dispersion of
atmospheric pollutants .
Z
0
T
Ⅳ Fumigation(薰烟扩散)
• P113, Figure 5.15
summary
Stable atmosphere (low actual lapse rates or
inversions ) and low wind speed lead to highest
ground –level pollutant concentrations .
Unstable , and high wind speed lead to lowest
ground-level pollutant concentrations .
This Lecture and the Next Lecture
 This Lecture:
 Chapter 5
Page 83~101
Page 111~115
 The Next Lecture:
 Chapter 6
Page 119~146
Homework
5.8 (Page 116)
Which are four ways to produce a
temperature inversion? (Page 111)
DISCUSSION
Topics about Air pollution:
 Introducing yourself
 Interesting news or information about air pollution your
having read or heard
 Your opinions on this Air Pollution course
 Your suggestions for Chinese Air Pollution
 Other familiar issues about Air Pollution