Light scattering by nonspherical raindrops

Ceilometer-Based Rain-Rate Estimation: A Case-Study Comparison With S-Band Radar and Disdrometer Retrievals in the Context of VORTEX-SE

“…According to [21] and [23], a key assumption to using the correlation between the RR and the atmospheric optical extinction derived from fixed-orientation ceilometer measurements (RR-to-extinction models; hereafter, RR-α models) is that droplets maintain symmetry in the direction of fall (i.e., assumption of small (spherical) drops and no canting [10, p. 249]). Otherwise, geometric optics calculations of light scattering by nonspherical raindrops reveal a strong dependence on the phase matrix that invalidate ceilometer measurements [24], [25]. More recently, Roy and Bissonnette [26] showed that rain extinction coefficients and depolarization ratios varied strongly depending on the lidar zenith angle (0-75 • ), demonstrating the importance of performing measurements with constant lidar scan direction.…”

Fast reactive control for illumination through rain and snow

“…Second, it is not necessary to consider drops that are too small to reflect a significant amount of light [15]. Finally, strong visibility improvement can be achieved well below perfect accuracy of the system.…”

Lidar remote sensing and co-operative observations: Processing methods and aerosol radiative transfer

“…In order to correlate RR and atmospheric optical extinction (RR-to-extinction models; hereafter, RR- models) retrieved form fixed-orientation ceilometer signals, must be kept in mind that droplets maintan symmetry in the fall direction [Rensch and Long, 1970;Vasseur and Gibbins, 1996]. Otherwise, geometric optics calculations of light scattering by non-spherical raindrops reveal a strong dependence on the phase matrix that invalidate ceilometer measurements [Kokhanovsky and Macke, 1997;Macke and Großklaus, 1998]. Besides it is worth noting the importance of the fixed-orientation, since rain extinction coefficients vary strongly depending on the laser beam zenith angle [Roy and Bissonnette, 2001].…”