1. Session 2, Unit 3 Atmospheric Thermodynamics

2. Ideal Gas Law
Various forms

3. Hydrostatic Equation
Air density change with atmospheric pressure

4. First Law of Thermodynamics
For a body of unit mass
dq=Differential increment of heat added to the body
dw=Differential element of work done by the body
du=Differential increase in internal energy of the body

5. Heat Capacity
At constant volume
At constant pressure

6. Heat Capacity
Relationships

7. Concept of an Air Parcel
An air parcel of infinitesimal dimensions that is assumed to be
Thermally insulated – adiabatic
Same pressure as the environmental air at the same level – in hydrostatic equilibrium
Moving slowly – kinetic energy is a negligible fraction of its total energy

8. Adiabatic Process
Reversible adiabatic process of air

9. Lapse Rate Combine hydrostatic equation and ideal gas law
For adiabatic process

10. Lapse Rate
Therefore
dT/dz is Dry Adiabatic Lapse Rate (DALR)

11. Dry Adiabatic Lapse Rate
Dry adiabatic lapse rate (DALR)
Or on a unit mass basis
Or the expression in the textbook:

12. Lapse Rate Effect of moisture Because
Wet adiabatic lapse rate < DALR (temperature decreases slower as air parcel rises)
Condensation

13. Lapse Rate Superadiabatic lapse rate (e.g., 12oC/km)
Subadiabatic lapse rate (e.g., 8oC/km)
Atmospheric lapse rate
Factors that change atmospheric temperature profile
Standard atmosphere (lapse rate ~ 6.49 oC/km or 3.56 oF/1000 ft)

14. Potential Temperature
Current state: T, P
Adiabatically change to: To, Po
Set Po = 1000 mb, To is potential temperature 
If an air parcel is subject to only adiabatic transformation,  remains constant
Potential temperature gradient

15. Session 2, Unit 4 Turbulence and Mixing Air Pollution Climatology

16. Atmospheric Turbulence
Turbulent flows – irregular, random, and cannot be accurately predicted
Eddies (or swirls) – Macroscopic random fluctuations from the “average” flow
Thermal eddies
Convection
Mechanical eddies
Shear forces produced when air moves across a rough surface

17. Lapse Rate and Stability
Neutral
Stable
Unstable

18. Richardson Number and Stability
Stability parameter
Richardson number
Stable
Neutral
Unstable

19. Stability Classification Schemes
Pasquill-Gifford Stability Classification
Determined based on
Surface wind
Insolation
Six classes: A through F
Turner’s Stability Classification
Wind speed
Net radiation index
Seven classes
Feasible to computerize

20. Inversions Definition Types Fumigation Radiation inversion
Evaporation inversion
Advection inversion
Frontal inversion
Subsidence inversion
Fumigation

21. Planetary Boundary Layer
Turbulent layer created by a drag on atmosphere by the earth’s surface
Also referred to as mixing height
Inversion may determine mixing height

22. Planetary Boundary Layer
Neutral conditions
Mixing height
Increased wind speed and surface roughness cause higher h.

23. Planetary Boundary Layer
Unstable conditions
Mixing height

24. Planetary Boundary Layer
Stable conditions
Mixing height

25. Surface Layer Fluxes of momentum, heat, and moisture remain constant
About lower 10% of mixing layer

26. Surface Layer Monin-Obukhov length
Monin-Obukhov length and stability classes

27. Surface Layer Wind Structure
Neutral air

28. Surface Layer Wind Structure
Unstable and stable air

29. Friction Velocity
Measurements of wind speed at multiple levels can be used to determine both u* and z0

30. Power Law for Wind Profile
Wind profile power law
Value of p

31. Estimation of Monin-Obukhov Length
For unstable air
For stable air
Bulk Richardson Number

32. Air Pollution Climatology
Meteorology vs. climatology
Meteorological measurements and surveys
Pollution potential -low level inversion frequency in US

33. Air Pollution Climatology
Mean maximum mixing height
determined by
Morning temperature sounding
Maximum daytime temperature
DALR
Stability wind rose