The Winhaze Visual Air Quality Modeler characterizes the effect of pollutants on visual air quality at a number of locations throughout the U.S. It is the online adaptation of the Windows PC-based WinHaze Level Visual Air Quality Modeler software, developed by John Molenar of Air Resource Specialists, Inc. The most recent version of the software, 2.9.9.1, was last updated in 2012 and may be still available by special request. See https://www.air-resource.com for contact information. It is compatible with 32-bit Windows operating systems only.

The technologies and algorithms used to create the modeled images were originally described in a 1994 paper by John Molenar, William Malm, and Christopher Johnson titled Visual Air Quality Simulation Techniques Though it is beyond the scope of this document to describe those modeling techniques, the following information desribes how to use the site to create simulated images.

Winhaze starts with a pristine image of a scenic vista and uses aerosol and radiative transfer modeling to create two images with user specified visual impairment. The pristine images, distance masks (defining distances to geographic features in the image) and site specific data (Rayleigh scattering) for over 100 sites are built in to Winhaze.

Users cannot use their own images for modeling, but pre-modeled images created using software such as Terragen (https://planetside.co.uk/) are supported and can be added if they meet specifications and are approved.

Winhaze allows the user to create two simulated images: the base image, and the modeled image. Either image can have more impairment than the other, allowing simulation of improving or worsening visual air quality scenarios. The typical Winhaze procedure is:

• Select a site type from the option list.
• Select a site from the drop down list.
• Select the extinction input method from the option list.
• Enter the base and modeled extinction in the entry boxes, use regional haze values, or compute them from aerosol species data. Only selected sites currently have or have had IMPROVE monitoring and the associated aerosol species and regional haze metric data available.
• Click the Model Images button.
• For premodeled Terragen images the process is similar. The images with visibility closest to the specified values will be used instead of new images being modeled. Click the Display Images button.

The extinction input method provides a choice of measurements:

• Atmospheric extinction (b_ext) measured in inverse megameters (Mm^-1)
• Visual range measured in kilometers (km) or miles (mi)
• Deciviews

The measurements are convertible to each other, so the choice depends on the user's requirements.

To use regional haze metrics, select either Natural Conditions or a monitoring year, the cleanest (G10), average (G50), haziest (G90) or most impaired 20% metric, and then click Use Selected Total b_ext.

The values entered for the base and modeled images are checked prior to modeling to ensure they are within acceptable ranges.

The modeled image can be split to show both the base and modeled impairment levels on the same image by checking Split Image and moving the slider to the desired split point (10 to 90%, left to right) prior to clicking Model Images or Display Images.