Module 7: Combustion and Environment
Lecture 36: Atmosphere
Atmosphere (Contd..)
Stratosphere
Region between tropopause (18 km) and stratopause (50 km).
Contains 9.5% of atmospheric mass.
The temperature increases from tropopause (220 K) to stratopause (280 K).
The chemicals from troposphere that are not destroyed are dissociated in this region.
CFC is converted into
HF and mixture of CI compounds.
The photochemistry in the stratosphere is strongly affected by ozone layer.
The short wavelength
cannot reach below 25 km due to the photochemistry.
This is how we are protected from the harmful UV rays.
Stratospheric
column is the major absorber of solar UV between 220 and 320 nm.
Depletion of ozone layer will change the tropospheric chemistry in two ways
Lowers the flux of
into troposphere
Enhances the production of OH
HF and mixture of CI compounds. 
cannot reach below 25 km due to the photochemistry. 
column is the major absorber of solar UV between 220 and 320 nm. 
