Blue moons and large fires.

Theoretical analysis of simulations of optical effects from the 1950 Canadian forest fires has revealed what conditions are necessary for large fires to cause blue moons and suns. This study shows how large fires can be used to improve our understanding of long range pollution transport on a global scale as well as the evolution of aerosol radiative effects so important to global climate studies. The most important aerosol characteristics are the initial submicron smoke particle concentration and areal extent of the fire and its effect on fire plume dispersion. Capping clouds above the fire and near saturation humidity effects are simulated and found to help establish anomalous optical effects. Data are included showing probable anomalous extinction events associated with concentrated fire plumes.