Initial layer thickness for doubling; governs accuracy, 10E-5 should be
adequate. Do not go beyond half the real precision, i.e. 10e-8 for REAL*8.
Default 1.e-05.
polradtran_max_delta_tau value
This option is only relevant for rte_solver polradtran.
Arve Kylling
2010-03-10