The Aerosol Model OPAC - Contents and New Software

OPAC (Optical Properties of Aerosols and Clouds) was published in 1998 as an aerosol and cloud model, consisting of a microphysical description of aerosol, as a combination of variable components, and clouds with different types. All relating optical properties, valid for 8 values of relative humidity, can be extracted from a database of Mie calculations covering the wavelength range from 0.2 to 40 micrometers. The extraction software is part of the package. OPAC has meanwhile been downloaded, and probably used, by several hundred researchers all over the world. Since 1998, new possibilities have been developed to describe the microphysical properties of particles and their corresponding radiative properties. Therefore, we intend to improve OPAC by introducing, for instance, nonspherical particles, an improved description of humidity effects, and additional aerosol components which may be missing. As a starting point for these improvements, the original OPAC Fortran77 software has been rewritten completely as an object oriented Python program. We will present the current status and planned future additions, as a basis for discussions about possible needs of the OPAC users.