Minimize Computation of Aerosol Parameters

This section includes:

  • aerosol interpolation
  • atmospheric correction

To obtain aerosol parameter values for the SYN collocated grid, the aerosol parameters retrieved for the SYN averaged grid have to be interpolated. Bilinear interpolation is sufficient.

Atmospheric correction uses look-up tables of radiative transfer calculations. All look-up tables undergo multidimensional linear interpolation according to their continuous coordinate variables (channel and aerosol model index numbers are discrete coordinate variables).

N-dimensional linear interpolation of a quantity in a Cartesian parameter space can be divided into two steps:

  1. Normalisation of input parameters in accordance with the equation below, where Pl and Pu are the nearest lower and upper parameter entries, respectively, in the look-up table.
  2. Interpolation by a weighted sum of the nearest tabulated values.

There are two variants of atmospheric correction algorithms: variant A is used in the aerosol retrieval processing step, while variant S retrieves final surface reflectance and errors.

The final atmospheric correction is also carried out for pixels marked as cloudy in order to provide surface reflectance and error for cases where cloud screening was not appropriate.