ATOC 4720: class 17ATOC 4720: class 17

Atmospheric aerosolsAtmospheric aerosols Effects on atmospheric phenomenaEffects on atmospheric phenomena

Total concentrationTotal concentration

Concentration vary with location and time.Generally, Over the ocean:

Rural land areas:

Polluted air:

>10km, H=7km;<5km, H=3km.

Size spectraSize spectra<0.2um;0.2-2um;>2um

Similar

Sources and sinks:

Aitken nuclei

Combustion processes (human activities, Forest fires, volcanoes, gas-to-particle Conversion;)

[1]

[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.

Life time: Aitken nuclei: <1hour in polluted Air or in clouds;Large: days;Giant: minutes-hours-days.

Level-dependent:

Average Residence Time of Aerosols in Atmosphere

10

100

1000

104

105

106

107

108

0.0001 0.001 0.01 0.1 1 10 100 1000

Jaenicke, 1980

Average Residence Time, seconds

Radius, micrometer

Below 1.5 km

MiddleTroposphere

Tropopause

1 Day

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.

TRANSPORT:

Desert Aerosol Transport over North Africa and the Mediterranean.

Largest values Tend to be along The dust plume trajectories

Effects on atmospheric Effects on atmospheric phenomenaphenomena

[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.