Intro to Atmospheric Chemistry (GGS 319)

What are the greenhouse gasses ?
Methane, Carbon Dioxide, Ozone, CFCs, Water Vapor, Nitrous Oxide,
Natural Greenhouse Gasses v.
Anthropogenic Gasses
Natural- Methane, Carbon Dioxide, and Nitrous Oxide
Relationship between Greenhouse Gasses and Temperature
A positive relationship, as one increases the other increases (Increase in Temp 0.6 K and Greenhouse gasses have increased)
Impact on Climate and Climate Change
Global upper ocean heat content is rising
Planck’s Law
Amount of radiation emitted from a blackbodies
yields the smooth curves of intensity as a function of
wavelength for an emitter at a given temperature

h = 6.6262?10-34 J s (Planck’s Constant )
K = 1.3807?10-23 J K-1 (Boltzmann’s Constant )
c = 2.998 x 108 ms-1 speed of electromagnetic radiation
? = wavelength

Wien’s Displacement Law
Max Wavelength = 2897/T
Speaks about peak height of thermal spectrum of an object is inversely proportional to its temperature
Stefan-Boltzmann Law
The flux of radiation (R) emitted by a blackbody

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R =?T4

? = 5.67?10-8 W m-2 K-4

Kirchhoff’s Law
A body absorbs and emits energy at a given wavelength with equal efficiency

Blackbody A?= ?? =1
Nonblackbody A?= ?? < 1

Emissivity – ratio of energy flux at the surface of wavelength over the ideal energy flux of a blackbody in the same range
x 2?r – Particle Size Parameter

Rayleigh Scattering (x << ?)
Small particles are much more efficient
at scattering than larger particles

Radiactive forcing
Is the level of influence an force of altering the balance between incoming and outgoing energy

?Ts =??F
?Ts = equilibrium surface temperature
?F = radiative forcing
? = c limate sensitivity coefficinet

Ozone distribution in the atmosphere
– triatomic ozone
– naturally in stratosphere ( 20 km above the surface of the earth)
– The natural ozone layer: vertical and latitudinal distribution of
ozone number of density (1012 molecules cm-3)
Function of Ozone layer: UV absorption by ozone
-atmospheric constituent (absorbs 180 and 290 nm)
-product of an oxygen only environment
– cyanobacteria contributed it to the environment
Ozone formation: The chapman mechanism
– Ozone formed from photolysis of the atmospheric 0^2
– Bond energy of the 0^2 corresponds to the energy of a 240 nm UV proton
– only photons of waves less than 240 nm can photolyze the O^2 molecule ( high energy protons are present in solar spectrum)
Catalytic Ozone Destruction: Missing elements
Hydrogen oxides
Nitrogen oxides
Ozone hole
What are the major chemical components of the atmosphere?
Oxygen, hydrogen, nitrogen, carbon
Atmospheric Layers and their major characteristics:
troposphere (9 – 16km) – PBL, adiabatic lapse rate at 6.5, well mixed, pollution and weather
Stratosphere 16 – 50 km
Ozone layer, not well mixed, no precipitation or clouds, pollutants alter the radiation budget
mesosphere 50 -85 km
coldest temperature occurs, temperature decreases
conversion of solar heat to sensible heat
Temperature profiles of all the layers
when the temperature of air increases with height (stratosphere)
Environmental Lapse Rate
rate at which temperature decreases with height (6.5 in thermosphere)
Planetary Boundary Layer
the point directly influence by surface presence and responds to a time scale of an hour
Planetary Boundary layer structure
Ground surface, viscos sublayer, the surface layer, transition layer, free atmosphere
Planetary Boundary Significance
Pollution gets trapped there, weather/temperature is there , people live there
importance of spectral gab
a spectrum where eddies are well mannered and well displayed- small eddies=small time periods. Peak time
3 time periods (24 hours, large scale, microscale). Peak shows eddies that contributed the most TFR. Microscale eddies has range between 10 seconds and 10 mins.
What is atmospheric dispersion
process where pollutants expands, mixes, and diluted by atmospheric motion deleted by clouds
Turbulent transport
diffusion by eddies, – consists of a lot of eddies – usually decides turbulence spectrum;
3 kinds of turbulent transport
mechanical turbulence
Wind Shear(caused)
turbulence caused by bouyance
Characteristics of pollutant behavior
looping- plume is characteristic of neutral or slightly stable atmospheric conditions
Fumington- ML begins to grow, eventually reaching the height of the elevated plume from the previous nightin stable atmosphere, horizontal with little vertical dispersion
conning – in the RL with vertical and horizontal spread
Difference between PBL Layer with free atmosphere
PBL- adiabatic, turbulent
Free Atmosphere- well mized, not turbulent
Early evolution of the atmosphere
volcanic gases, presence of H20,Carbon Dioxide, Nitrogen, and Sulfur gasses
– billions of years later water took shape and creatuin of cyano bacteria
Atmospheric Composition
Nitrogen – 78%, Oxygen 21%, and 1% other
Mixing Ratio
Mixing ratio = mass of water vapor (grams)
mass of dry air (kilograms)
Number of density
molecules per volume
Partial density
partial / all
Properties of atmosphere
Ideal gas law
p = ?RT
Temperature and Pressure Profile
Factors affecting vertical velocity
Factors affecting horizontal wind
Effects of heating and cooling
The simplest model: One box model
The simplest model: One box model
Mass balance
Multi-Box models