Physical Principles of the Greenhouse Effect

The major source of OH radicals is ozone photolysis with short wavelength UV radiation this produces excited oxygen atoms, O( D), which rapidly react with water vapor, forming OH  

NOj is easily photolyzed and therefore its daytime concentration is very low. 

Peroxyacetyl nitrate (PAN), CH3C000N02, is also a source of OH radicals when it thermally decomposes  

decomposition of PAN in the presence of NO can lead to the formation of OH radicals and conversion of NO to NOj merely from thermal reactions. This could be very important because PAN can be an indicator of the urban ozone-forming potential (see Section 8.4.1) and of the organic-oxidizing capacity of the urban air mass. The thermal decomposition of PAN also leads to the formation of NOj radicals. 

R is the radius of the planet a is the Stefan-Boltzmann constant (5.67 x 10-8 Wm-2), and Tis the temperature of the Earth. An additional consideration has to be made the conceptual absorbing disk perpendicular to the solar radiation has an area of TtR2, and this factor multiplies the EA term. 

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