Interagency Monitoring of Protected Visual Environments

Visibility has improved dramatically in the US, due largely to the Clean Air Act and Regional Haze Rule.

Our National Parks and Wilderness Areas possess many stunning vistas and scenery. Unfortunately, these scenes are diminished by uniform haze causing discoloration and loss of texture and visual range. Layered hazes and plume blight also detract from the scene.  Recognizing the importance of visual air quality, congress included legislation in the 1977 Clean Air Act to prevent future and remedy existing visibility impairment in Class I areas.  To aid in the implementation of this legislation, the IMPROVE program was initiated in 1985.  This program implemented an extensive long term monitoring program to establish the current visibility conditions, track changes in visibility and determine causal mechanism for the visibility impairment in the National Parks and Wilderness Areas.

As the result of reduced emissions due to the Clean Air Act and Regional Haze Rule, as well as the ongoing efforts of IMPROVE and other state, regional and national programs, visibility has improved dramatically in the US.  However, new sources related to climate change and oil and gas development are expected to impact all aspects of air quality in the US, including visibility, and continued efforts are needed to ensure that impacts from new and existing sources are well understood and controlled.

News & Updates

A new Data Advisory has been posted regarding Increased variation of humidity in the weighing laboratory.

Visibility, the Seeing of Near and Distant Landscape Features (Malm, 2016) has been published.

 A paper describing the Earlier onset of the spring fine dust season in the southwester United States has been published in GRL.

 An overview paper on the Bakken Air Quality study has been published in Atmospheric Chemistry and Physics.

The 2015 IMPROVE Steering Committee Meeting Presentations and Summary are available.

A new data advisory has been added on the bias between masked and unmasked light absorption measurements.

Three new data advisories have been added addressing the re-delivery of IMPROVE data from 2005 - 2014; change to artifact correction method for OC fractions; and a change in the reporting of filter absorption.

The 2014 IMPROVE Steering Committee Meeting Presentations and Summary are available.

A presentation on the results and recommendations from the committee to review and revise on how best to correct for the positive organic artifact in the IMPROVE and CSN monitoring programs has been posted to the Gray Literature section.

The Regional Haze Rule Summary Data are now available through 1988 - 2014.

Simulated photographs using WinHaze visualizing changes in haze over 9 or more years (Hand et al., 2014) have been added.