Climatology Lecture 5

1
ClimatologyLecture 5
Vertical Motion in the Atmosphere Continued...

• Michael Palmer
• Room 119, Atmospheric Physics
• mpalmer_at_atm.ox.ac.uk

2
Dry Example Absolute Stability Surface Temp 34
oC
Stable Air No convection No Rain
Environ Temp
Parcel Temp
Temperature
3
Dry Example Absolute Stability Surface Temp 34
oC
Stable Air No convection No Rain
Environ Temp
Parcel Temp
Temperature
4
Moist Example Absolute Instability Surface Temp
34 oC
Unstable Air Convection Rain
Condensation Level
Parcel Temp
Temperature
Environ Temp
5
Wet Example Conditional Instability
Unstable Air Convection Rain
Level of free convection
Condensation Level
Temperature
6
Vertical Motion

• Potential Instability
• Absolute Stability Topographically forced stable
  cloud Pollution dispersion climatology

7
Potential Instability

• Conditional instability involves convective
  ascent of parcels of air
• Potential instability involves large scale ascent
  of layers of air
• Instability is potential since the air is stable
  until lifted by an appropriate amount
• Potential Instability may occur if a layer of air
  is very moist at the bottom but very dry aloft

8
Stability depends on ELR
Temperature
Environ Temp
Parcel Temp
9
Stability depends on ELR
Temperature
Environ Temp
Parcel Temp
10
Z
Temperature
11
B
New ELR
A
Z
B
Old ELR
A
Temperature
12
Z
B
A
Temperature
13
A
Z
A
Temperature
14
B
A
Z
B
A
Temperature
15
B
Z
A
B
A
Temperature
16
B
More unstable
A
Z
B
Stable
A
Temperature
17
Potential Instability

• The initial lapse rate in the layer AB is stable
• On lifting of the entire layer, the base reaches
  condensation quickly, since it is moist - the
  slower rate of cooling (SALR) is applicable - but
  the top of the layer cools at the DALR
• The new layer AB is unstable for rising parcels.

18
Vertical Motion

• Potential Instability
• Absolute Stability Topographically forced stable
  cloud Pollution dispersion climatology

19
Absolute Stability
??
20
Absolute Stability
21
Absolute Stability
22
Environmental lapse rate
Z
Dry adiabatic lapse rate
Temperature
23
Environmental lapse rate
1
Z
Dry adiabatic lapse rate
Temperature
24
Environmental lapse rate
1
Z
Dry adiabatic lapse rate
2
Temperature
25
Environmental lapse rate
1
3
Z
Dry adiabatic lapse rate
2
Temperature
26
Environmental lapse rate
1
3
4
Z
Dry adiabatic lapse rate
2
Temperature
27
Environmental lapse rate
1
3
5
4
Z
Dry adiabatic lapse rate
2
Temperature
28
Absolute Stability
1
3
4
2
29
Absolute Stability
30
Absolute Stability
Air hotter and drier on leeward side
31
(No Transcript)
32
(No Transcript)
33
(No Transcript)
34
(No Transcript)
35
H E I G H T
TEMPERATURE
36
H E I G H T
Subsidence Inversion
TEMPERATURE
37
H E I G H T
Subsidence Inversion
Surface Radiation Inversion
TEMPERATURE
38
H E I G H T
Early Morning
TEMPERATURE
39
H E I G H T
Daytime
Early Morning
TEMPERATURE
40
(No Transcript)
41
(No Transcript)
42
(No Transcript)
43
(Unstable)
(Near neutral stability)
G (dashed) DALR Solid - ELR
44
(No Transcript)
45
(No Transcript)
46
(No Transcript)
47
(No Transcript)
48
(No Transcript)
49
Stack Height

• Statistical characteristics of surface and
  non-surface inversion layers depth, strength,
  frequency
• longer stacks increased eddy diffusion
• effective stack height H hs dh
• hs physical height of stack
• dh f (Stability, wind speed,stack exit
  velocity, stack diameter, temperature of
  emission, emission rate)

50
(No Transcript)
51
(No Transcript)
52
(No Transcript)
53
Readings for todays lecture

• Barry and Chorley 1997 p76-86
• Briggs et al. 1997 Fundamentals of the Physical
  Environment p78-88
• Henderson-Sellers and Robinson 1999 p56-74
• Linacre and Geerts 1997 Climates and Weather
  Explained p127-145
• McIlveen 1992 p109-139
• Oke, 1990 Boundary Layer Climates