Addition of an Aerosol Transmission Model to the Aeronautical Systems Division Infra-Red Emission Prediction Program (ASDIR)

摘要

The Aeronautical Systems Division Infra-Red Emission Program (ASDIR) is a large computer program used to predict hot surface and plume emissions from a geometrically modeled target. The atmospheric transmission segment of the program included only the major gaseous absorbers (H2O, CO2, and N2O) with no aerosol attenuation. To improve the flexibility of the program in making more accurate predictions at low altitudes, an aerosol transmission computational scheme was written for the ASDIR code. Using the basic methodology in the transmission model LOWTRAN 4, a subroutine, was written for direct inclusion into ASDIR. Curve fits of the following LOWTRAN parameters were performed which simplified the aerosol procedures and minimized the additional computer storage and time requirements in ASDIR: assumed aerosol particle densities, equivalent sea level path lengths for vertical paths - AV(z), and total sea level extinction coefficients for an 'average continental' and 'maritime' aerosol models. Results of the new subroutine (called HAZE) compared very well with LOWTRAN's aerosol predictions. A logic change was included in HAZE to automatically select a maritime aerosol model under low visibility conditions. This programming change was prompted by results of a recent Grafenwohr, FRG transmission study.