Atoc 4720 class 17
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ATOC 4720: class 17. Atmospheric aerosols Effects on atmospheric phenomena. Total concentration. Concentration vary with location and time. Generally,. Over the ocean:. Rural land areas:. Polluted air:. >10km, H=7km; <5km, H=3km. Size spectra. <0.2um ;. 0.2-2um; >2um. Similar.

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ATOC 4720: class 17

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ATOC 4720: class 17

  • Atmospheric aerosols

  • Effects on atmospheric phenomena


Total concentration


Concentration vary with location and time.

Generally,

Over the ocean:

Rural land areas:

Polluted air:

>10km, H=7km;

<5km, H=3km.


Size spectra

<0.2um;

0.2-2um;

>2um

Similar


Sources and sinks:

Aitken nuclei

[1]

Combustion processes (human activities,

Forest fires, volcanoes, gas-to-particle

Conversion;)

[2] Large to giant aerosol:

wind blown dust, emission of pollens,

and spores from plants; Ocean: bursting of

Air bubbles (under high windspeed); urban

Industrial processes.


Sinks: Aitken nuclei--big aerosols:

Precipitation and gravity.

Global: Precipitation 80-90%;

10-20%: gravitational settling.

Aitken nuclei: <1hour in polluted

Air or in clouds;

Large: days;

Giant: minutes-hours-days.

Life time:

Level-dependent:


Average Residence Time of Aerosols in Atmosphere


TRANSPORT:

Desert Aerosol Transport over North Africa and the Mediterranean.

The 2D distribution of aerosols

Concentration for the period

from August, 1996 to April, 2000 (top panel).

Main source regions of the UV-absorbing aerosols can be inferred, and these regions are marked in the bottom panel.


Desert Aerosol Transport over North Africa and the Mediterranean.

Largest values

Tend to be along

The dust plume

trajectories


Effects on atmospheric phenomena

[1] Clouds and precipitation:

Good: Precitaion; bad: acid rain


[2] Electricity: electric field

and conductivity;

measurements of

electricity may indicate aerosol

concentration;


nuclei

Electric field


[3] Radiation

Scattering & absorption of solar radiation:

Important for the earth’s radiation budget;

Qr at the earth’s surface can cause

SST (sea surface temperature) variability,

And thus force variability in atmospheric

Circulation and convection: affecting

Climate.


[4] Chemistry:

Liquid aerosol absorbs gases: react;

Solid aerosol provide surfaces upon which

Gases can be absorbed and react;

Aerosol & sulfur dioxide from polluted air

accumulate in stable (T-inversion),

moist air==sulfur dioxide is converted

to sulfates==smog;

1952 Landon smog caused 4000 people death.


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