*TAN Section |
Section | Flags | Field | Type | Description | Range | ||
---|---|---|---|---|---|---|---|
(any) | (any) | TANFIL | C200 | Name of a Data File | |||
Limb-viewing | |||||||
*TAN | TAN | R | Actual (refracted) tangent heights [km] | Within atmospheric altitude range | |||
*GEO | GEO | R | Projected (geometric) tangent heights [km] | -Radius of Curvature:top of atmosphere | |||
*ELE | ELE | R | Elevation angles [deg] relative to observer horizontal, usually negative=viewing below the horizontal | Observer outside atmosphere: -90:(top *HGT level
after refraction) Observer within atmosphere: -90:+90 ZEN Flag: 0.1:+90 NAD Flag: -90:-0.1 | |||
*SEC | NAD or ZEN | SEC | R | Airmass factors (=sec(zenith angle)) [dimensionless], for plane-parallel atmospheres | ≥1.0 (1=vertical path) | ||
*LEV | FLX | LEV | R | Altitude levels [km] for flux calculation outputs. | Within atmospheric altitude range .atm file | ||
*LEN | HOM | LEN | R | Path lengths [km] for homogeneous path calculations. | >0 | ||
" | UNITS=UNITS | C2 | Units for homogeneous path length | km, m, cm or mm | |||
*DIM | TAB | See [specific page] for record structure. |
χ = k ρ swhere ρ is the absorber density. The aim is to set ρs =1 mol m^{-2}, so that, numerically, χ=k.
Expanding ρ, for standard atmospheric pressure and temperature 296 K, assuming a volume mixing ratio of 1 ppmv
s = (1 mol m^{-2} ) ( R T )/( v p )
= (1 mol m^{-2} ) ( 8.3145 J mol^{-1} K^{-1} x 296 K) / ( 10^{-6} x 1013.25 Pa )
= 2.4289 x 10^{6} m = 2428.9 km
*TAN paths.tan ! list of tangent heights from a standard scan pattern. 40 41 42 ! additional paths at 40, 41, 42 km,
*SEC 1 ! Direct nadir view only
*ELE -90, -1.5, -0.5, 0.0, 0.5, 1.5 ! [deg] nadir, plus views towards limb
*LEN UNITS=cm 50.3 ! Output filenames will be, eg tra_50300.asc