Characteristics of Droplet Size Distributions in Low-Level Stratiform Clouds Observed from Tokyo Skytree

Continuous observations of cloud droplet size distributions (DSDs) in low-level stratiform clouds have been conducted at a height of 458 m from Tokyo Skytree (a 634-m-high broadcasting tower in Tokyo) using a cloud droplet spectrometer. In this report, the characteristics of cloud parameters related to the cloud DSD from June to December 2016 are presented. The mean cloud droplet number concentration ( N c ), average diameters, and effective diameters of cloud droplets in non-drizzling clouds were 213 cm −3 , 7.3 μm, and 9.5 μm, respectively, which are close to the reported values for continental stratiform clouds. The relationship between liquid water content (LWC; g m −3 ), N c (cm −3 ), and radar reflectivity ( Z ; mm 6 m −3 ) was estimated as LWC = 0.17 N c 0.50 Z 0.45 , with a coefficient of determination ( R 2 ) of 0.93. The observed cloud DSDs were well fitted by a lognormal distribution, and the average median diameter of the fitted DSD was 6.6 μm.