1. BASIC METEOROLOGICAL PROCESSES

2. Objectives What is atmospheric thermodynamics?
What are the variables of atmospheric thermodynamics?
What is lapse rate?
Explain the potential temperature.
What is atmospheric stability and the various methods that define atmospheric stability?
What is boundary layer development?
What are the effects of meteorology on plume dispersion?
What is wind velocity profile?
What is wind rose diagram and what are the uses of it?
Determination of mixing height.

3. Air Pollution Meteorology
Atmospheric thermodynamics
Atmospheric stability
Boundary layer development
Effect of meteorology on plume dispersion

4. Atmosphere
Pollution cloud is interpreted by the chemical composition and physical characteristics of the atmosphere
Concentration of gases in the atmosphere varies from trace levels to very high levels
Nitrogen and oxygen are the main constituents. Some constituents such as water vapor vary in space and time.
Four major layers of earth’s atmosphere are:
Troposphere
Stratosphere
Mesosphere
Thermosphere

5. Atmospheric Thermodynamics
A parcel of air is defined using the state variables
Three important state variables are density, pressure and temperature
The units and dimensions for the state variables are
Density
(mass/volume)
gm/cm3
ML-3
Pressure (Force/Area)
N/m2 ( Pa )
ML-1T-2
Temperature
o F, o R, o C, o K T
Humidity is the fourth important variable that gives the amount of water vapor present in a sample of moist air

6. Equation of State
Relationship between the three state variables may be written as:
f ( P, ρ ,T) = 0
For a perfect gas:
P = ρ .R .T
R is Specific gas constant
R for dry air = Joules / gm /oK
R for water vapor = Joules / gm /oK
R for wet air is not constant and depend on mixing ratio

7. Exercise
Calculate the density of a gas with a molecular weight of 1 atm (absolute) and 80 oF. Gas constant, R = ft3atm/lb- moleoR.

8. Solution Absolute Temperature = 80 oF + 460 = 540 oR
Density = P ( molecular weight) / RT
Density = ( 1atm. )*(29 lb/lb mole) / ( ft3atm/lb-moleoR)*(540 oR)
Density = lb/ ft3.

9. Exercise
Determine the pressure, both absolute and gauge, exerted at the bottom of the column of liquid 1 meter high, with density of kg / m3.

10. Solution
Step 1 :
Pgauge = (density of liquid) * ( acceleration due to gravity) *(height of liquid column)
Step 2 : Pabsolute = Pgauge + Patmospheric
Pabsolute = kPa

11. Laws of Thermodynamics
First Law of Thermodynamics:
This law is based on law of conservation of total energy.
Heat added per unit mass = (Change in internal energy per unit mass) (Work done by a unit mass) 
δH = δU+δW
Second Law of Thermodynamics:
This law can be stated as "no cyclic process exists having the transference of heat from a colder to hotter body as its sole effect"

12. Specific Heat
Defined as the amount of heat needed to change the temperature of unit mass by 1oK.
Specific heat at constant volume
Cv = lim δQ
δT→0 δT α = const
Specific heat at constant pressure
Cp = lim δQ
δT→0 δT p = const
Relationship between Cv and Cp is given by Carnot’s law:
For perfect gas, Cp – Cv = R
For dry air Cp = (7/2)*R (Perfect diatomic gas)
Cv = (5/2)*R (Perfect diatomic gas)
Ratio of Cp and Cv for dry air is 1.4
Cpd = joules/gm/o K ; Cvd = joules/gm/o K

13. Processes in the Atmosphere
An air parcel follows several different paths when it moves from one point to another point in the atmosphere. These are:
Isobaric change – constant pressure
Isosteric change – constant volume
Isothermal change – constant temperature
Isentropic change – constant entropy (E)
Adiabatic Process – δQ = 0 (no heat is added or
removed )
The adiabatic law is P. αγ = constant
E =

14. Statics of the Atmosphere
Vertical variation of the parameters = ?
Hydrostatic Equation:
Pressure variation in a "motionless" atmosphere
Pressure variation in an atmosphere:
Relationship between pressure and elevation using gas law:

15. Statics of the Atmosphere
Integration of the above equation gives
Using the initial condition Z=0, P = P0
The above equation indicates that the variation of pressure depends on vertical profile of temperature.
For iso-thermal atmosphere
Therefore, pressure decreases exponentially with height at a ratio of mb per 100m.

16. Potential Temperature:
Lapse Rate:
Lapse rate is the rate of change of temperature with height
Lapse rate is defined as Γ = -δT δz
Value of  Γ varies throughout the atmosphere
Potential Temperature:
Concept of potential temperature is useful in comparing two air parcels at same temperatures and different pressures.

17. Concept of Potential Temperatureθ

18. Atmosphere Stability
The ability of the atmosphere to enhance or to resist atmospheric motions
Influences the vertical movement of air.
If the air parcels tend to sink back to their initial level after the lifting exerted on them stops, the atmosphere is stable.
If the air parcels tend to rise vertically on their own, even when the lifting exerted on them stops, the atmosphere is unstable.
If the air parcels tend to remain where they are after lifting stops, the atmosphere is neutral.

19. Atmospheric Stability
The stability depends on the ratio of suppression to generation of turbulence
The stability at any given time will depend upon static stability ( related to change in temperature with height ), thermal turbulence ( caused by solar heating ), and mechanical turbulence (a function of wind speed and surface roughness).

20. Atmospheric Stability
Atmospheric stability can be determined using adiabatic lapse rate.
Γ > Γd
Unstable
Γ = Γd
Neutral
Γ < Γd
Stable
Γ is environmental lapse rate
Γd is dry adiabatic lapse rate (10c/100m) and dT/dZ = -10c /100 m

21. Atmospheric Stability Classification
Schemes to define atmospheric stability are:
P- G Method
P-G / NWS Method
The STAR Method
BNL Scheme
Sigma Phi Method
Sigma Omega Method
Modified Sigma Theta Method
NRC Temperature Difference Method
Wind Speed ratio (UR) Method
Radiation Index Method
AERMOD Method (Stable and Convective cases)

22. Pasquill-gifford Stability Categories
Surface Wind Speed (m/s)
Daytime Insolation
Nighttime cloud cover
Strong
Moderate
Slight
Thinly overcast or 4/8 low cloud
3/8
< 2 A 
A - B B -
2 - 3 C E F
3 - 5
B - C D
5 - 6
C - D
> 6
Source: Met Monitoring Guide – Table 6.3

23. Sigma Theta stability classification
CATEGORY
PASQUILL CLASS
SIGMA THETA (ST)
EXTREME UNSTABLE A
ST>=22.5
MODERATE UNSTABLE B
22.5>ST>=17.5
SLIGHTLY UNSTABLE C
17.5>ST>=12.5
NEUTRAL D
12.5>ST>=7.5
SLIGHTLY STABLE E
7.5>ST>= 3.8
MODERATE STABLE F
3.8>ST>=2.1
EXTREMELY STABLE G
2.1>ST
Source: Atmospheric Stability – Methods & Measurements (NUMUG - Oct 2003)

24. Temperature Difference (∆T)
Source: Regulatory guide; office of nuclear regulatory research- Table 1

25. Turbulence
Fluctuations in wind flow which have a frequency of more than 2 cycles/ hr
Types of Turbulence
Mechanical Turbulence
Convective Turbulence
Clear Air Turbulence
Wake Turbulence

26. Local CLIMATOLOGICAL data - Toledo

27. Weather conditions of toledo

28. Weather Station
Home, Professional, and Live

29. Weather Balloon
Pressure, Temperature, Wind Speed, Wind Direction, & Humidity

30. Use of Towers
Velocity, Temperature, & Turbulence

31. Local CLIMATOLOGICAL data - Toledo
Snowfall
Temperature
Annual
38.3”
December
9.1”
January
9.8”
February
8.0”
March
6.3”
Annual
49.6°F
January
25.7°F
July
73.2°F
Precipitation
Annual
31.62”
January
2.18”
June
3.45”
Greatest snowfall – 73.1” ( )
Least snowfall – 6.0” ( )
Average number of days with a tenth of an inch or more snowfall – 27 days

32. National Weather Map
US Forecast

33. National Air Quality
Ozone

34. Climate
Temperature

35. National Weather Map H – High Pressure Area L – Low Pressure Area
A high pressure area forecasts clear skies.
A low pressure area forecasts cloudiness and precipitation

36. Boundary Layer Development

37. Boundary Layer Development
Thermal boundary Layer (TBL) development depends on two factors:
Convectively produced turbulence
Mechanically produced turbulence
Development of TBL can be predicted by two distinct approaches:
Theoretical approach
Experimental studies

38. Boundary Layer Development
Theoretical approach may be classified into three groups:
Empirical formulae
Analytical solutions
Numerical models
One layer models
Higher order closure models

39. TBL using Analytical Solution
Time

40. Effects of Meteorology on Plume Dispersion

41. Effects of Meteorology on Plume Dispersion
Dispersion of emission into atmosphere depends on various meteorological factors.
Height of thermal boundary layer is one of the important factors responsible for high ground level concentrations
At 9 AM pollutants are pulled to the ground by convective eddies
Spread of plume is restricted in vertical due to thermal boundary height at this time

42. Wind Velocity
A power law profile is used to describe the variation of wind speed with height in the surface boundary layer
U = U1 (Z/Z1)p
Where,
U1 is the velocity at Z1 (usually 10 m)
U is the velocity at height Z.
The values of p are given in the following table.
Stability Class
Rural p
Urban p
Very Unstable
0.07
0.15
Neutral
0.25
Very Stable
0.55
0.30

43. Beaufort Scale
This scale is helpful in getting an idea on the magnitude of wind speed from real life observations
Atmospheric
condition
Wind speed
Comments
Calm
< 1mph
Smoke rises vertically
Light breeze
5 mph
Wind felt on face
Gentle breeze
10 mph
Leaves in constant motion
Strong
25 mph
Large branches in motion
Violent storm
60 mph
Wide spread damage

44. Wind Rose Diagram (WRD)
Wind Direction (%)
Wind Speed (mph)

45. Wind Rose Diagram (WRD)
WRD provides the graphical summary of the frequency distribution of wind direction and wind speed over a period of time
Steps to develop a wind rose diagram from hourly observations are:
Analysis for wind direction
Determination of frequency of wind in a given wind direction
Analysis for mean wind speed
Preparation of polar diagram

46. Calculations for Wind Rose
% Frequency =
Number of observations * 100/Total Number of Observations
Direction: N, NNE, ,NNW, Calm
Wind speed: Calm, 1-3, 4-6, 7-10,

47. Determination of Maximum Mixing Height
Steps to determine the maximum mixing height for a day are:
Plot the temperature profile, if needed
Plot the maximum surface temperature for the day on the graph for morning temperature profile
Draw dry adiabatic line from a point of maximum surface temperature to a point where it intersects the morning temperature profile
Read the corresponding height above ground at the point of intersection obtained. This is the maximum mixing height for the day

48. Determination of Maximum Mixing Height

49. Power plant Plumes in Michigan
Monroe Power Plant

50. Power plant Plumes in Michigan
Trenton Channel

51. Power plant Plumes in Michigan
Belle River Power Plant
River Rouge Power Plant
Photo credit:  Kimberly M. Coburn

52. PROBLEMS

53. During an air pollution experiment the lapse rate was a constant at 1
During an air pollution experiment the lapse rate was a constant at 1.1 °C per 100 m. If the atmosphere is assumed to behave as a perfect gas and the sea level temperature and pressure were 16 °C and 1 atm, at what altitude was the pressure one-third the sea level?

54. Solution Step1: Step 2: Step 3: Substitute for temperature Step 4:
Calculate Temperature
Step 3:
Substitute for temperature
Step 4:
Integrate between P = 1 and P = 0.333, and between z = 0, and z = z.
Z = m

55. References
Met Monitoring Guide:
Regulatory Guide – office of nuclear regulatory research:
reactors/active/01-023/01-023r1.pdf
NOAA-National Climate Data Center