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

The 2020 Field Maintenance Schedule has been posted.

The 2019 Technical System Audit Report has been posted.

 The 2018 Quality Assurance Report for the IMPROVE Network has been posted.

The agenda and presentations and photos have been posted from the 2019 IMPROVE Steering Committee Meeting.

A new paper examining the IMPROVE algorithm for estimating light extinction has been published.

A new Data Advisory describing universal calibration constants for flow rate calculation has been posted.

The 2018 Ions QA Report has been posted.

The updated 2017 RHR files have been posted.

Updated SOPs have been posted for IMPROVE Operations, filter absorbtion, and XRF analysis.

A new Data Advisory describing a Change in analytical protocol for XRF analysis has been posted.

The Technical System Audit Report with results from 2016-2018 is now available.

A new Data Advisory describing a Method change for calibrating flow rate transfer standards has been posted.

The semi-annual Quality Assurance Report for the IMPROVE Network has been posted (April 2019).

A new Data Advisory describing Changes to the HIPS System has been posted.

A new Data Advisory describing Updated data for Carbon has been posted.

A new Data Advisory describing Correction of chloride concentrations for filter blank levels has been posted.

An overview describing the new Impairment Metric is now available.

A new paper describing Trends in PM2.5 Residual Mass from IMPROVE measurements has been published.