Switch on sampling of cloud properties (reff/tau/dlwc) by photons. This option needs mc_backward. The optical properties contributing to the result for each pixel are integrated using the photon weight p_{{weight,n}} in the following way:

{\langle r_{e}\rangle}_{\textrm{wc}}^{\textrm{tau}}\,=\,\frac{\sum\limits _{{n=0}}^{{photons}}\, p_{{weight,n}}\, r_{{\textrm{wc},n}}}{\sum\limits _{{n=0}}^{{photons}}\, p_{{weight,n}}}\qquad r_{{\textrm{wc}}}\,=\,\frac{\int _{0}^{\tau}\ \tau _{{\textrm{w}}}r_{{\textrm{ew}}}\,\mathrm{d}\tau}{\int _{0}^{\tau}\tau _{{\textrm{w}}}\,\mathrm{d}\tau}

For each internal wavelength, one [basename]_[wvl].cldprp file with the following format is created where values marked with top are taken at first cloud contact:  

ix iy {\langle r_{e}\rangle}^{\textrm{tau}}_{\textrm{wc}} {\langle r_{e}\rangle}^{\textrm{tau}}_{\textrm{ic}} {\langle r_{e}\rangle}^{\textrm{hit}}_{\textrm{wc}} {\langle r_{e}\rangle}^{\textrm{hit}}_{\textrm{ic}} {\langle\tau\rangle}_{\textrm{wc}} {\langle\tau\rangle}_{\textrm{mc}} \nabla LWC \nabla IWC

 
Values denoted with hit are taken at the last cloud contact before hitting the sensor, while the the water content gradient is taken at the last cloud scattering before hitting the sensor (information about cloud surface orientation).