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

Abstract

 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 the liquid water content (LWC; g m^-3), N_c (cm^-3) and radar reflectivity (Z; mm⁶ m^-3) was estimated as LWC = 0.17N_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.