l5 mike

ClimatologyLecture 5: 

Climatology Lecture 5 Michael Palmer Room 119, Atmospheric Physics mpalmer@atm.ox.ac.uk ‘Vertical Motion in the Atmosphere’ …Continued...

Slide2: 

Temperature Dry Example: Absolute Stability Surface Temp = 34 oC Parcel Temp Environ Temp Stable Air No convection No Rain

Slide3: 

Temperature Dry Example: Absolute Stability Surface Temp = 34 oC Parcel Temp Environ Temp Stable Air No convection No Rain

Slide4: 

Temperature Moist Example: Absolute Instability Surface Temp = 34 oC Parcel Temp Environ Temp Unstable Air Convection Rain Condensation Level

Slide5: 

Temperature Wet Example: Conditional Instability Level of free convection Condensation Level Unstable Air Convection Rain

Vertical Motion: 

Vertical Motion Potential Instability Absolute Stability Topographically forced stable cloud Pollution dispersion climatology

Potential Instability: 

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

Slide8: 

Temperature Parcel Temp Environ Temp Stability depends on ELR

Slide9: 

Temperature Parcel Temp Environ Temp Stability depends on ELR

Slide10: 

Temperature Z

Slide11: 

Temperature Z A B A’ B’ Old ELR New ELR

Slide12: 

Temperature Z A B

Slide13: 

Temperature Z A A’

Slide14: 

Temperature Z A B A’ B’

Slide15: 

Temperature Z A B A’ B’

Slide16: 

Temperature Z A B A’ B’ Stable More unstable

Potential Instability: 

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 A’B’ is unstable for rising parcels.

Vertical Motion: 

Vertical Motion Potential Instability Absolute Stability Topographically forced stable cloud Pollution dispersion climatology

Slide19: 

Absolute Stability ??

Slide20: 

Absolute Stability

Slide21: 

Absolute Stability

Slide22: 

Temperature Z Environmental lapse rate Dry adiabatic lapse rate

Slide23: 

Temperature Z 1 Environmental lapse rate Dry adiabatic lapse rate

Slide24: 

Temperature Z 1 Environmental lapse rate Dry adiabatic lapse rate 2

Slide25: 

Temperature Z 1 Environmental lapse rate Dry adiabatic lapse rate 2 3

Slide26: 

Temperature Z 1 Environmental lapse rate Dry adiabatic lapse rate 2 3 4

Slide27: 

Temperature Z 1 Environmental lapse rate Dry adiabatic lapse rate 2 3 4 5

Slide28: 

Absolute Stability 1 2 3 4

Slide29: 

Absolute Stability

Slide30: 

Absolute Stability Air hotter and drier on leeward side

Slide35: 

H E I G H T TEMPERATURE

Slide36: 

H E I G H T TEMPERATURE Subsidence Inversion

Slide37: 

H E I G H T TEMPERATURE Surface Radiation Inversion Subsidence Inversion

Slide38: 

H E I G H T TEMPERATURE Early Morning

Slide39: 

H E I G H T TEMPERATURE Early Morning Daytime

Slide43: 

Γ (dashed) – DALR Solid - ELR (Unstable) (Near neutral stability)

Stack Height: 

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)

Readings for today’s lecture: 

Readings for today’s 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