If NOPRNT is set to −1 for multiple scattering calculations, spectral diffuse and total flux values along the lines
of sight will be written to tape8. These values are 1 cm
-1
spectral resolution results (0.1, 5 or 15 cm
-1
results if the
0.1, 5 or 15 cm
-1
band model data file is used, respectively). Spectral flux values convolved with the instrument slit
function are output to the 'specflux' or 'rootname.flx' file if FLAGS(7:7) is not left blank (CARD 4). Be warned that
setting NOPRNT to −1 for long paths (e.g., ground to space) over a large spectral range (e.g., 0.4 to 0.7 µm) will
generate large tape8 files.
TPTEMP > 0. Boundary temperature [K] of 'image pixel' (i.e., at H2), used in the radiation mode
(if IEMSCT = 1, 2 or 4) for slant paths that intersect the earth OR terminate at a
gray boundary (for example, cloud, target). If the 'area-average' temperature
(AATEMP, CARD 4A) is not entered and the line-of-sight intersects the earth,
TPTEMP is also used as the lower boundary temperature in the multiple scattering
models.
0. No surface emission if H2 is above ground. If the path intersects the Earth and
TPTEMP is either not positive or left blank, MODTRAN
®
uses the temperature of
the first atmospheric level as the boundary temperature. If the 'area-average'
temperature (AATEMP, CARD 4A) is not entered and the line-of-sight intersects
the earth, the temperature of the first atmospheric level is also used as the lower
boundary temperature in the multiple scattering models.
SURREF = 'BRDF' (or the first non-blank character is 'B' or 'b') Surface spectral BRDFs (Bidirectional
Reflectance Distribution Functions) are specified by CARD 4A, 4B1, 4B2 and 4B3
inputs.
= 'LAMBER' (or the first non-blank character is 'L' or 'l') Spectral Lambertian surface(s) is (are)
specified by CARD 4A, 4L1 and 4L2 inputs.
0. or blank Albedo of the earth (and at H2 if TPTEMP > 0), equal to one minus the surface
emissivity and spectrally independent (constant). If the value exceeds one, the
albedo is set to 1; if SURREF is blank, the albedo is set to 0.
< 0 Negative integer values allow the user to access pre-stored spectrally variable
surface albedos from the 'DATA/spec_alb.dat' file.
The file 'DATA/spec_alb.dat' is a replacement for the 'DATA/refbkg' file used in MODTRAN
®
3.7 and earlier
versions of the model. The current version contains 46 surfaces. A complete list is provided in Sec. 17.6. These are
only meant to be representative of the types of options available; the user is encouraged to add to the set or replace
the existing ones. Instructions for adding surfaces to the 'spec_alb.dat' file are provided directly within the file. It is
recommended that the wavelength limits on the surface properties match or exceed the spectral range specified for
the MODTRAN
®
run. MODTRAN
®
will use the endpoint values at any wavelength outside this range (no
extrapolations). Table 1 summarizes the use of selected CARD 1 parameters: MODTRN, SPEED, MODEL,
ITYPE, IEMSCT, IMULT, MDEF, NOPRNT and SURREF.
4. CARD 1A (REQUIRED) – RADIATIVE TRANSPORT DRIVER CONT’D
CARD 1A inputs enable selection of scattering options, scaling of molecular profiles, customizing of the top-
of-atmosphere (TOA) solar irradiance, specification of data files, and Angstrom Law perturbations of aerosol optical
properties:
CARD 1A: DIS, DISAZM, DISALB, NSTR, SFWHM, CO2MX, H2OSTR, O3STR, C_PROF, LSUNFL,
LBMNAM, LFLTNM, H2OAER, CDTDIR, SOLCON, CDASTM, ASTMC, ASTMX, ASTMO,
AERRH, NSSALB
FORMAT(3A1, I3, F4.0, F10.0, 2A10, 2A1, 4(1X, A1), F10.0, A1, F9.0, 3F10.0, I10)
DIS = t, f (blank), s Used if IMULT = ±1 in CARD 1. Set DIS to TRUE (T or t) to activate the
DISORT discrete ordinate multiple scattering algorithm. If DIS is FALSE (F, f
or blank), the less accurate but faster Isaac’s two-stream algorithm is used.
New to MODTRAN
®
5 is another value for DIS, S (or s). If S is chosen,
DISORT calculations are performed at selected spectral points in the
atmospheric window regions. These handfuls of DISORT radiances are then
used to scale Isaac’s values for the entire wavelength region.