a camada de ozÔnio - ib.unicamp.br20-%20ne441%20%202013/1a%20aula/... · the ozone layer is a...
TRANSCRIPT
The ozone layer is a layer of ozone gas which surrounds
the Earth some 15 to 35 km above its surface in the
stratosphere This 20 km wide layer acts like a natural filter
because it prevents most of the sun's ultraviolet rays from
reaching the Earth.
This natural ozone layer accounts for about 90% of all the
ozone gas that exists. As we have seen, it is very beneficial. In
fact, let us call it "good" ozone.
The other 10% is "bad" ozone and comes from sources
such as the exhaust from cars. But because this ozone is
located down near the Earth' s surface, it gets trapped in the
summer months in air pockets and causes smog over our cities.
This type of air pollution has a bad effect on people who suffer
from breathing problems. That's why we call it "bad" ozone and
that's why many governments are working hard to get rid of it
The illustration above shows a column of air, 10 deg x 5 deg, over
Labrador, Canada. The amount of ozone in this column (i.e. covering the
10 x 5 deg area) is conveniently measured in Dobson Units.
If all the ozone in this column were to be compressed to standard
temperature and pressure (STP) (0 deg C and 1 atmosphere pressure)
and spread out evenly over the area, it would form a slab
approximately 3mm thick. 1 Dobson Unit (DU) is defined to be 0.01 mm
thickness at STP; the ozone layer over Labrador then is 300 DU.
Total ozone amount during October at Halley. Data in yellow
pre-date the discovery of the Ozone hole in 1985 Fonte BAS
TOMS (Total Ozone Mapping Spectrometer) is a satellite-
borne instrument used to gain a global picture of ozone levels.
Because they scatter and absorb incoming sunlight, aerosol particles exert a
cooling effect on the Earth's surface. The Pinatubo eruption increased aerosol
optical depth in the stratosphere by a factor of 10 to 100 times normal levels
measured prior to the eruption. Consequently, over the next 15 months,
scientists measured a drop in the average global temperature of about
0.6 oC
In June 15, 2001, Mount
Pinatubo in the Philippines
erupted with a tremendous
force, ejecting vast amounts of
ash and gas high into the
atmosphere; so high that the
volcano's plume penetrated into
the stratosphere. Pinatubo
injected about 15 million tons of
sulfur dioxide into the
stratosphere, where it reacted
with water to form a hazy layer
of aerosol particles composed
primarily of sulfuric acid
droplets
Scientists use data from
NASA’s Total Ozone
Mapping Spectrometer
(TOMS) to measure the
relative amount of
aerosols—solid or liquid
particles suspended in the
atmosphere.
This image shows dust
blowing from the Sahara
Desert into the Atlantic
Ocean, more dust from the
Rub al Khali and Nafud
deserts of the Arabian
Penninsula, and what may
be smoke over northern
India.