Visibility has been monitored at this federally mandated Class I area since 1995 following the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocols. The charts below are based upon the analysis of particulate matter data that include estimates of visibility conditions and the amount of light extinction attributed to different types of particulate matter measured at this IMPROVE monitoring site.
The Regional Haze Program relies upon the haze index to track two different trends: visibility on the haziest days annually and on the clearest days annually. Both trends are measured beginning with the 2000-2004 "baseline" period. The haziest days are also compared to the goal of no manmade impairment in 2064. The haze index has a unit of measure called deciview and a one unit change in deciview may be noticeable under certain conditions. Higher deciview values correspond to hazier scenes. Click here to learn more about how the calculations are conducted, and how the glide paths were established.
The top figure below shows the haziest and clearest annual deciview values for the entire data record for this monitoring site. The red line represents the haziest day "glide path" connecting the baseline conditions to the 2064 goal, and is intended to be a guide in gauging progress at this Class I area. The 2011 through 2015 5-year average (of available data) indicates the haze index is below the glide path, with all of the past 4 years below the red line in the graph below. On the clearest days, all of the past 4 years have been below the 6.75 deciview baseline (green line below). Furthermore, the 5-year average on the clearest day is below the baseline. Visibility on the clearest days is not to degrade from the baseline.
Between 2011 and 2015 , ammonium sulfate was the primary particle in the atmosphere contributing to the light extinction observed on the days classified with the haziest conditions (middle figure). On the clearest days, ammonium sulfate was also the primary particle contributing to light extinction (bottom figure). Click here to learn more about the fine particles that impair visibility.
|Haze Index Results||
|Haziest Results - Fine Particles Contribution to Light Extinction|
|Clearest Results - Fine Particles Contributions to Light Extinction|
The X- and Y- axes can be adjusted. Click and drag your mouse along the axes to scroll through the values. To adjust the scale of the axes, click and drag your mouse along the axes while holding the shift key and left mouse button.
The X-axis adjusts on each graph in unison with other graphs, while the Y-axes adjust independent of the other graphs.
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Type an amount into one of the data fields (left) and then select with your mouse one of the other two boxes to see the calculated amount in the other two fields.
United States Environmental Protection Agency. 2003. Guidance for Tracking Progress Under the Regional Haze Rule. EPA-454/B-03-004. Office of Air Quality Planning Standards Emissions, Monitoring and Analysis Division. Research Triangle Park, NC. 96pp.