The stratosphere is the second layer of the atmosphere, ranging from 20-50km above the troposphere. Within the stratosphere, temperature increases with altitude. The ozone layer resides in the stratosphere, absorbing UV light and protecting the Earth. Some bacteria and birds can survive in the lower stratosphere. Ozone is formed through reactions involving oxygen and free radicals, and is constantly being produced and destroyed through absorption of UV light, maintaining a steady state. However, ozone-depleting pollutants like CFCs and NOx disrupt this balance, causing ozone depletion.

1. GUIDED BY :-
GUJARAT TECH. UNIVERSITY
A.D PATEL INSITUTE OF TECHNOLOGY
NEW VALLABVIDHYANAGAR
2110007-ENVIRONMENTAL STUDIES
STRATOSPHERE
PREPARED BY :-
VEER PATEL
ACADEMIC YEAR 2017-18

2. STRATOSPHERE
THE SECOND LAYER OFTHE EARTH’S
ATMOSPHERE

3. Information on Stratosphere
 The Stratosphere is the
second layer of the
atmosphere above the
troposphere ranging from
about 20 km to 50 km altitude.
 The density declines in the
layer from 100g/m3 to g/m3.
 The temperature remains
constant at the lower layer of
the stratosphere and then
rises with increasing altitude.
 At the top of the stratosphere
the thin air may reach
temperature close to 0 C (273
K).
 Ozone Layer lies in
stratosphere

4.  It is stratified in temperature, with warmer
layers higher up and cooler layers farther
down.
 At moderate latitudes the stratosphere is
situated between about 10–13 km and 50
km altitude above the surface, while at the
poles it starts at about 8 km altitude, and
near the equator it may start at altitudes as
high as 18 km

5.  Within this layer,
temperature increases
as altitude increases.
The top of the
stratosphere has a
temperature of about
−3°C just slightly
below the freezing
point of water.
 Methane ,while not a
direct cause of ozone
destruction in the
stratosphere, does
lead to the formation
of compounds that
destroy ozone.
Picture of Stratosphere

6.  The border between the
troposphere
and stratosphere ,
the tropopause, marks
where this temperature
inversion begins.
 Temperatures vary within
the stratosphere with the
seasons, in particular
with the polar
night(winter).
 The greatest variation of
temperature takes place
over the poles in the
lower stratosphere;
variations at lower
latitudes and higher
altitudes are smaller.

7. Life
Bacteria
 Bacterial life survives in the stratosphere, making it a part
of the biosphere. In 2001 an Indian experiment, involving
a high-altitude balloon, was carried out at a height of 41 km
and a sample of dust was collected with bacterial material
inside.
Birds
 Some bird species have been reported to fly at the lower
levels of the stratosphere. On November 29, 1973,
a Rüppell’s vulture (Gyps rueppelli) was ingested into a jet
engine 11,278 m (37,000 ft) above the Ivory Coast, and bar-
headed geese (Anser indicus) reportedly overfly Mount
Everest’s summit, which is 8,848 m (29,029 ft).

8. OZONE IN THE STRATOSPHERE
 A thin layer of ozone gas (03) encircles the earth, in the
stratosphere.
 03 is a natural occurring bluish gas which has an acrid
 odor. It has harmful effects on organisms however, it
helps block out the harmful UV rays 15km to 45km up in
the atmosphere.
 It is located between 12 km to 50 km above the Earth.
 The function of it is to prevent 99% of the sun’s
 ultraviolet light.

9. FORMATION OF OZONE
 1) O2 2 O* (Oxygen free radical)
2) O2 + O* O3
The ozone is formed when the double bond in
the oxygen is broken by very short wavelength
UV light. An oxygen n free radical is therefore
formed, this oxygen free radical further reacts
with another oxygen atom to form the ozone
gas, O3

10. OZONE DEPLETION
 The reverse process happens when O3
absorbs longer wavelength UV light.This is
because two pi bonding electrons are shared
between the entire structure therefore it has
weaker bonds compared to O2.
 O3 (g) O2 (g) + ●O (g)
 The oxygen free radicals react with another
resonance structure to form O2.
O (g) + O3 (g) O2 (g)

11. STEADY STATE
 As a result the rate of which Ozone is
produced and depleted would be equal, this is
know as the steady state.
 The ozone helps protects the earth from
dangerous UV light by this process, however,
this steady state is constantly being
interfered by ozone-depleting pollutants.

12. OZONE DEPLETING POLLUTANTS
 The main pollutants includes: CFCs (Chlorofluorocarbons)
and oxides of oxygen. (NOx)
Sources
 CFCs are mainly found in hair spray or deodorant cans as
a propellant, old refrigerators, air conditioners e.t.c.
 Oxides of nitrogen are formed from high temperature
reactions of N2 and O2 in supersonic aircraft engines and
lightning.
 As an effect, the ozone would deplete much quicker
compared to the ozone formed.