Seasonal Variations

• Variations in sunlight intensity cause variations in O₃ production rate.
• When the sun is most intense (i.e., Summer), O₃ should reach highest levels, and primary pollutants should be at low concentrations.
• In the winter, when the sun is weak, there will be reduced production of O₃.
• Primary pollutants, such as CO, reach seasonal maxima during the winter, but more from the lower mixing heights during this season than from the reduced sunlight intensity.  
• The effect of low mixing heights would be to reduce the dispersion volume in which pollutants can mix, which increases the concentration if the source rate is the same.