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ATOC 4720 class 42: Final review
1. Composition of the present atmosphere and its
evolution
The first two major composition of the present
atmosphere:
: 75.51% by mass;
: 23.14% by mass;
Evolution: The earth formed first, and its
present atmosphere are believed
to be evolved from the volatile
substance from volcanic eruption.
Major composition of the raw atmosphere due to
volcanic eruption: 85%
, and 10%
light
2. The distribution of
atmospheric pressure and density
Where
: 7-8 km; scale height;
3. The fair weather elecric field
and charged particles
Charged Particles: important for lightening, reflection of radio
waves, fair weather electric field, etc
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4. Temperature distribution with
height
5. Gas laws
For a unit mass dry air:
For unit mass of moist air:
Where Virtual temperature
6. The hydrostatic equation
Large scale atmospheric motions satisfy hydrostatic balance.
Balance between the upward PGF and the downward gravitational
Force.
PGF
Gravity
7. The geopotential and
geopotential height
: the work that must be done against the earht’s
Gravitational field in order to raise a mass of 1kg
From sea level to that point. J/kg.
Geopotential height:
8. The hypsometric equation
Warm air: thicker
Cold air: thinner;
9. The first law of
thermodynamics
Applies for both diabetic and adiabatic processes.
Diabetic: heat absorbed by a substance is used either to increase
its internal energy or used to do external work.
Adiabatic: dq=0. [1] Adiabatic expansion;
[2] Adiabetic compression;
10. Lifting condensation level
(LCL)
The lifting condensation level is defined as the level to which
a parcel of moist air can be lifted adiabatically before it becomes
saturated with respect to a plane surface of water.
LCL -- well defined cloud base.
11. Static stability and level of
free convection
Conditionally unstable;
Level of free convection
x
LCL
Temperature
: unstable;
T1=T1e; then T2>T2e
T2e
T2
T1
T2e
: stable;
Convectively unstable; T inversion layer;
12. Atmospheric aerosols
Effects on cloud and precipitation: CCN; Should know why.
Homogeneous nucleation is difficult to grow big;
Atmoshperic electricity, radiation, chemistry.
13. Hurricanes
Dynamics:
CISK;
Air/sea interaction;
Thermally direct
Circulation:
Available Potential
Energy (PE)
Is converted to
Kinetic energy (KE).
Maintenance: warm
Core maintenance-PE--KE;
14. Radiation
Wien displacement law:
Stefan-Boltzmann law:
Kirchhoff’s law:
15. The global energy balance
Top:
100% in
30% reflection
38%+26% atm emits;
6% IR emits Earth;
Atm:
16%+3% SW abs;
15% IR abs;
7% abs sensible;
23% abs latent;
38% emits molecules;
26% emits clouds;
Surface: 51% in;
23% latent;
7% sensible;
21% IR;
16. Photoionization, photodissociation
of oxygen, and fromation of ozone
layer
Upper thermosphere, photoionization of molecules and atoms
Produces ionosphere, absorbs solar radiation:
Photodissociation above 100km:
Ozone is not formed in this high level however; mean free path
Large, 3 body collision chance is small.
20-60km: O is trace but important for ozone formation.
Three body clission chance is large because mean free
Path is small.
Then,
Reduce UV, Ozone layer protects the earth plants etc.