Air Resource Specialists, Inc.


Software Downloads

Click to Access WinHaze

WinHaze is a visual air quality modeler that simulates visual air quality differences of various scenes. The online adapatation of the original Windows PC-based software allows analysts to view visual air quality scenarios on their screen as a supplement to air quality monitoring. Available scenes include 144 national park, wilderness, and urban scenes. Users first select a scene, then model it using different optical parameters or aerosol species to simulate these effects on the scene.

The PC-based software is only compatible with 32-bit Windows operating systems and is no longer supported. The software was last updated in 2012 and Version can be downloaded here: WinHaze setup.EXE


BackMC is a backward photon trajectory, multiple scattering, Monte Carlo, radiation-transfer model used calculate sky radiances. The wavelength dependent, scattered radiation, intensity and polarization parameters are computed as a function of the observer elevation and azimuthal viewing angles. The two main advantages of the Monte Carlo method over other radiative transfer methods are (1) with the proper input, the ability to simulate any complex, inhomogeneous, spherical atmosphere, multiple scattering scenarios and (2) the use of statistical sampling to solve the radiative transfer equation. The solution is obtained by averaging the radiance from many individual photon path results. Each photon can participate in as many interactions as possible in which each scattering or absorption event behaves randomly according to the appropriate probability distribution. These probabilities are directly determined from physical principles. The model contains no more limiting assumptions or approximations than those inherent in the descriptions of the each probability distribution. BackMC has been thoroughly tested and compared to analytical solutions for Rayleigh atmospheres, published results from various model calculations of aerosol atmospheres, and sky and plume radiance measurements with excellent results.

BackMC was originally developed in the early 1970's by Steven Cox and Thomas McKee of the Department of Atmospheric Science at Colorado State University. Many others added to the code between 1974 and the mid-1990s. A final report describing the code as it existed in 1987 is included in this zip file: "Backward Monte Carlo Computations of Radiation Propagating in Horizontally Inhomogeneous Media: Part I: Description of Codes", Tsay,, September 15, 1987. Since 1998 John V. Molenar of Air Resource Specialists, Inc. has maintained the code.