This preview shows pages 1–3. Sign up to view the full content.
39th International Physics Olympiad  Hanoi  Vietnam  2008
Theoretical Problem No. 3
CHANGE OF AIR TEMPERATURE WITH ALTITUDE,
ATMOSPHERIC STABILITY AND AIR POLLUTION
Vertical motion of air governs many atmospheric processes, such as the formation of
clouds and precipitation and the dispersal of air pollutants. If the atmosphere is
stable
,
vertical motion is restricted and air pollutants tend to be accumulated around the
emission site rather than dispersed and diluted. Meanwhile, in an
unstable
atmosphere,
vertical motion of air encourages the vertical dispersal of air pollutants. Therefore, the
pollutants’ concentrations depend not only on the strength of emission sources but also
on the
stability
of the atmosphere.
We shall determine the atmospheric stability by using the concept of
air parcel
in
meteorology and compare the temperature of the air parcel rising or sinking adiabatically
in the atmosphere to that of the surrounding air. We will see that in many cases an air
parcel containing air pollutants and rising from the ground will come to rest at a certain
altitude, called a
mixing height
. The greater the mixing height, the lower the air pollutant
concentration. We will evaluate the mixing height and the concentration of carbon
monoxide emitted by motorbikes in the Hanoi metropolitan area for a
morning rush
hour scenario, in which the vertical mixing is restricted due to a temperature inversion
(air temperature increases with altitude) at elevations above 119 m.
Let us consider the air as an ideal diatomic gas, with molar mass
μ
= 29 g/mol.
Quasi equilibrium adiabatic transformation obey the equation
, where
const
pV
γ
=
p
V
c
c
=
is the ratio between isobaric and isochoric heat capacities of the gas.
The student may use the following data if necessary:
The universal gas constant is
R
=
8.31 J/(mol.K).
The atmospheric pressure on ground is
0
p
=
101.3 kPa
The acceleration due to gravity is constant,
g
=
9.81 m/s
2
The molar isobaric heat capacity is
7
2
p
c
=
R
for air.
The molar isochoric heat capacity is
5
2
V
c
=
R
for air.
1
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document39th International Physics Olympiad  Hanoi  Vietnam  2008
Theoretical Problem No. 3
Mathematical hints
a.
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '11
 NA
 Physics

Click to edit the document details