Regional Visibility 50th Percentile ("Average Visibility Days")
This indicator measures regional visibility on an "average" day in the non-urbanized areas of the Tahoe Basin. Visibility is a measure of the distance at which an object or light can be clearly discerned by the human eye. Visibility can be impaired by airborne pollutants from local, regional, and global sources. Sources of locally generated pollutants include entrained/suspended roadway particles, vehicle emissions, residential wood burning, campfires, prescribed fires, and wildfires. Some particles responsible for the degradation of regional visibility in the Tahoe Basin include dust and other pollutants transported into the Basin from areas as far as Asia, and record-setting catastrophic wildfires throughout California and the western states in the last five years. Regional programs such as decreasing the number of polluting wood stoves and work to improve forest health to prevent or limit severe wildfire aim to increase regional visibility. Regional visibility is monitored at DL Bliss State Park as part of the national IMPROVE monitoring network.
Status
Regional visibility conditions monitored at the DL Bliss IMPROVE monitoring station.
Evaluation Map
Regional visibility monitoring station at DL Bliss State Park.
2019 Evaluation
- Status
- Considerably Better Than Target
- Trend
- Moderate Improvement
- Confidence
- High
Applicable Standard
AQ5: Achieve an extinction coefficient of 25 Mm-1 at least 50 percent of the time as calculated from aerosol species concentrations measured at the Bliss State Park monitoring site (visual range of 156 km, 97 miles).
Key Points
- Average visibility days at the non-urban DL Bliss State Park site show a long-term improvement since monitoring began in the early 1990’s and are well within air quality standards.
Delivering and Measuring Success
EIP Indicators
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Non-Compliant Wood Stoves Removed or Retrofitted
This EIP performance measure tracks removal of polluting wood stoves to reduce local air pollution for human and ecosystem health.
Example EIP Projects
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Nonconforming Wood Stove Retrofit/Removal
Improvements in average visibility is mostly attributed to reductions in smoke from programs such as the movement to cleaner-burning wood stoves.
Monitoring Programs
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Regional Visibility Monitoring
Visibility monitoring data are collected, analyzed, and reported by the IMPROVE (national Interagency Monitoring of Protected Environments) network using nationally accepted protocols.