Nearly all of the planet's natural ozone in the atmosphere is found in the stratosphere. The thickness and distribution of this stratospheric ozone vary seasonally and by location. Ozone also occurs in the troposphere as a pollutant, often in photochemical smog. [Journal of the Atmospheric Sciences; v.50; 1033; 1993.] [Environmental Science and Technology; v34; 2324-29; 2000.]
