Prof. Jiakuan Yang Huazhong University of Science and Technology Air Pollution Control Engineering

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 RH ( Relative Humidity) P( Pressure) temperature density

Other two factors that affect vertical motion RH = humidity saturation humidity The ratio of the water content of the air M≈29 － 0.253RH ρ= PM / TR RH M ρ RH ( Relative Humidity) a

Other two factors that affect vertical motion Vertical distance P( Pressure) P ρ a = － ρg dP dz

Dry adiabatic lapse rate ( ) is used to describe the temperature decrease of an air parcel when the air parcel rise. Standard lapse rate ( ) is used to describe the temperature decrease of surrounding air (or atmosphere) when the height increase. 10 ℃ /km Actual lapse rate( )

Lecture 5 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 ( )

Z T 1km 23.4°C 30°C 23.4°C In the daytime, the nearer the ground, the higher temperature of the atmosphere. Actual lapse rate( )

(5) Atmospheric stability How do changes of the temperatures affect the atmospheric stability? Questions

(5)Atmospheric stability T( ℃ ) Z(m) Surrounding air Polluted air parcel 0

(5) Atmospheric stability T( ℃ ) Z(m) 0 Change of the polluted air parcel is the same. 10 ℃ /km However, the temperature distribution of the the surrounding air will change from time to time, and from one place to another place.

( a ) unstable Z0Z0 Z T T0T0 T1’T1’ Z1Z1 T1T1 When air parcel rises, T 1 ’ > T 1 air parcel will rise upper and upper. When air parcel falls, T 2 ’ < T 2 air parcel will rise upper and upper. T2T2 T2’T2’ 0

( b ) neutral T Z a = 0 0

( c ) stable T Z a 0

( d ) very stable T Z temperature inversion a 0

Temperature inversion Z Z T T 300m 10°C 21°C ( a ) Dawn ( b ) Dawn + 2h Vertical temperature distribution model at the various time. 00

Temperature inversion Z Z T T 300m 1800m 27°C ( c ) Dawn + 4h ( d ) Midafternoon Vertical temperature distribution model at the various time. 0 0

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 冷暖间逆温暖气上爬，形成锋面

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. T Z 0

Ⅳ Fumigation( 薰烟扩散 ) P113, Figure 5.15

summary Unstable, and high wind speed lead to lowest ground-level pollutant concentrations. Stable atmosphere (low actual lapse rates or inversions ) and low wind speed lead to highest 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