A CAMADA DE OZÔNIO

A Terra é azul.

Yuri Alekseyevich

Gagarin em 12 de

abril de 1961.

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.