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The Air Force Institute of Technology Center for Directed Energy (AFIT/CDE) has developed a first principles
atmospheric propagation and characterization model called the Laser Environmental Effects Definition and Reference or
LEEDR. This package enables the creation of profiles of temperature, pressure, water vapor content, optical turbulence,
and atmospheric particulates and hydrometeors as they relate to line-by-line layer extinction coefficient magnitude at
wavelengths from the UV to the RF. Worldwide seasonal, diurnal, and geographical variability in these parameters is
accessed from probability density function (PDF) databases using a variety of recently available resources to include the
Extreme and Percentile Environmental Reference Tables (ExPERT), the Master Database for Optical Turbulence
Research in Support of the Airborne Laser, and the Global Aerosol Data Set (GADS). GADS provides aerosol
constituent number densities on a 5° x 5° grid worldwide. ExPERT mapping software allows the LEEDR operator to
choose from specific site or regional upper air data to characterize correlated molecular absorption, aerosol absorption
and scattering by percentile. The integration of the Surface Marine Gridded Climatology database, the Advanced Navy
Aerosol Model (ANAM), and the Navy Surface Layer Optical Turbulence (NSLOT) model provides worldwide
coverage over all ocean regions on a 1° x 1° grid. Molecular scattering is computed based on Rayleigh theory.
Molecular absorption effects are computed for the top 13 absorbing species using line strength information from the
HITRAN 2004 database in conjunction with a community standard molecular absorption continuum code. Aerosol
scattering and absorption are computed with the Wiscombe Mie model. Each atmospheric particulate/hydrometeor is
evaluated based on its wavelength-dependent forward and off-axis scattering characteristics and absorption effects on
laser energy delivered at any wavelength from 0.355 μm to 8.6 m. LEEDR can also produce correlated optical turbulence
profiles in percentile format. In addition, probability of cloud free line of sight (CFLOS) for hundreds of land sites
worldwide is available in LEEDR. Effects of layers of fog, several types of rain and several types of water droplet and
ice clouds can also be considered. In addition to describing some of the underlying theory to the LEEDR calculations, this paper presents graphical results
for several different scenarios. These generic scenarios are meant to exemplify how LEEDR enables the physically
realistic data capture of atmospheric effects on electromagnetic propagation.
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