The Atmosphere



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X. Human Impact on Atmospheric Energy:

Human can alter the energy balance and thus the temperature of the atmosphere over different space and time-scales by deliberate or unconscious action with beneficial or harmful results.

The energy balance is altered by:

- changing the nature and composition of the atmosphere; and

- altering the character of the earth's surface.


The urban heat island effect can be explained in part by atmospheric change through heat release and pollution emission from city areas.
The heat storage capacity and dry surface character of city structures also contribute to the urban heat island effect.
Increased anthropogenic (man-made) accumulations of carbon dioxide have been implicated as a potential cause of global warming. Such warming may enhance aridity in the mid-latitudes and cause rising sea levels due to glacier melt.
Particulate emission, whether by natural or anthropogenic means, may contribute to a global cooling effect.
Human modification of the earth's surface albedo, in particular by desertification, may also be responsible for planetary cooling.
Table below shows the typical climatic changes caused by urbanization.

Typical climatic changes caused by urbanization



Type of change Comparison with rural env.

Temperature

Annual mean 0.5-1.0oC higher

Winter mean 1.0-3.0oC higher

Relative humidity

Annual mean 6 % lower

Winter 2 % lower

Summer 8 % lower

Dust particles 10 times more

Cloudiness

Cloud cover 5 - 10% more

Fog, winter 100 % more frequent

Fog, summer 30 % more frequent

Radiation

Total on horizontal surface 15-20 % less

Ultraviolet, winter 30 % less

Ultraviolet, summer 5 % less

Wind speed

Annual mean 20 -30 % lower

Extreme gusts 10 -20 % lower

Calms 5 - 20 % more

Precipitation



Amounts 5 - 10 % more

Days with over 0.5 cm 10 % more

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