Partially melting droplets strongly enhance lidar backscatter

There has been a long-standing problem in discrepancy between theoretical and observed backscatter by water clouds. Lidar ratios from water clouds are often much lower than what calculated out by Mie theory. In this study, we find the low lidar ratios of water clouds in CALIPSO lidar observations can be explained if we assume some large droplets with liquid spherical shells and ice cores. Using a light scattering model for layered spherical particles, we can produce lidar ratios similar to those from the CALIPSO data while assuming large droplets with ice cores in clouds. This study explains the reason of low lidar ratios for water clouds and provides a method for remotely sensing partially melting droplets.