LOS Flag

RFM Flags: Line-of-Sight Pointing Jacobians


Output additional spectra representing the gradient of, eg radiance, as a function of altitude or elevation angle

No Pointing Jacobian calculations

At least two tangent paths must be specified in the *TAN section
Incompatible with FLX, HOM, LEV, MTX, NAD, TAB and ZEN Flags

  1. Pointing Jacobians are distinct from Jacobians with respect to elements of the atmospheric profile (JAC Flag), and are defined by the tangent heights selected in the *TAN section of the driver table

  2. The spectra are calculated simply from the difference between the nominal output spectra: linear difference for the lowest and highest altitudes, gradient of a quadratic fit for any intermediate altitudes, so accuracy will depend on the user-defined tangent height spacing

  3. 'Perturbation' units (defined by the parameter PTBLOS in file ptbcon_dat.f90) are 0.001 of the units in the *TAN section, i.e., 0.001*km or 0.001*deg (if using *ELE instead of *TAN)

  4. Each nominal output spectral file, e.g. rad_a08000.asc will then have an associated pointing Jacobian file, e.g. rad_a08000_los.asc, the string "_los" being inserted into the filename immediately following the tangent height identification.

[none reported]