February 2001PM Data Analysis Workbook: Front Matter Table of Contents (5 of 5) USING PM DATA TO ASSESS VISIBILITY (Cont’d) Visibility Impairment and Regional Haze8 Visibility Measurements11 Relationship Between Light Scattering and PM 2.5 14 What Pollutants Contribute to PM 2.5 and Light Extinction on Days when Visibility is Impaired?16 Long-term Trends and Seasonal Patterns in Visibility22 Identifying Sources Contributing to Visibility Impairment29 Transport and Transformation of Atmospheric Particles and Gases Affecting Visibility30 Available Methods and Tools32 Available Visibility Data33 Summary34 References35 SubjectPage ix GLOSSARY AND ACRONYMS1 REFERENCES1 SubjectPage