MODTRAN Card deck/Tape5_Edit Tutorial Explanation of Parameters & Options

Card 1

Run capabilities: MODTRAN MODTRAN Correlated absorption coefficients (k) This option is most accurate but runs slow Lowtran (for historical comparison only)

Run time parameter used with the correlated K option: Slow – used when using 33 k values per spectral bin and only for upper atmosphere (>40km) cooling rates and weighting function calculations Medium – for 17 k values

Meteorological Data: Single-altitude meteorological data specified (cnst press, horizontal path only) Tropical Atm 15o N Latitude Mid-Latitude Summer/Winter 45o N Latitude (we usually use summer) Sub-Artic Summer/Winter 60o N Latitude 1976 US Standard Atm User-specified Model Atm (e.g. radiosonde data) is to be read in

Atm Line of Sight (LOS) path: Horizontal (cnst-pressure) path single layer, no refraction Vertical or slant path between 2 altitudes Vertical or slant path to space or ground

Mode of Execution of the Program: Transmissive mode Spectral thermal radiance (no sun/moon) mode Spectral thermal radiance plus solar/lunar radiance mode (if IMULT =0 only single scatter solar radiance is included) Directly transmitted spectral solar/lunar irradiance

Multiple Scattering Mode: With or Without Multiple Scattering option

M1-6 are used to modify or supplement user-specified altitude profiles for temperature, pressure, and default molecular gases as shown water ozone methane N20 carbon monoxide oxygen

MDEF is used to modify or supplement user-specified altitude profiles for temperature, pressure, and molecular gases such as: NO, SO2, NO2, ammonia, HNO3, & 13 “heavy molecules” – 9 CFC’s & CIONO2, HNO4, CCL4, and N2O5

Input Atmospheric Model: Normal Operation sequentially reuses the previously used atmospheric model for a series of cases For the first run or to run MODTRAN once user input data needs to be read in

Tape 6 (the output file) Control: Normal output operation Minimize printing of transmittance or radiance tables and atmospheric profiles Creates an additional output file (tape 8) which includes weighting functions in transmission mode or fluxes in radiation modes with multiple scattering on

Boundary Temperature [K] when greater than zero: In radiation mode at H2 for slants that intersect the earth or terminate at a grey boundary (cloud, target, etc.) If apparent area temperature (AATemp in Card 4) isn’t specified & LOS intersects the earth this is also the lower boundary temperature in multiple scattering models

Boundary Temperature [K] when  0 or Blank or Default: No surface emission if H2 is above ground If the path intersects the earth the first atmospheric level is used as the boundary temperature If AATemp is not entered and the LOS intersects the earth the temperature of the first atmospheric level the is also used as the lower bound for the multiple scattering model

Surface Albedo – one minus the surface emissivity and spectrally independent constant. The value can only be between 0 & 1. If the parameter is set to something greater than one it will default to one if the value is left blank it will default to zero.

negative numbers will correspond to pre-sorted spectrally Surface Albedo: negative numbers will correspond to pre-sorted spectrally variable surface albedos from a spectral library (some of these are described in the interface as shown, while there are still other options)