Calculate MYSTIC emission of each grid box; may need a considerable amount of memory,
depending on the 3D cloud grid. Note that emission is calculated directly without tracing
any photons which makes this option very fast. Increasing mc_photons will therefore
not affect the result. Only meaningful with rte_solver montecarlo and source thermal.
An optional argument W_per_m2_and_dz (default), W_per_m3, or K_per_day may
be specified which converts the result e.g. to heating rates. This option is only available
for forward calculations. For backward please use mc_backward_output emis.
Arve Kylling
2010-03-10