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 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.

Seasonal Changes of Airborne Bacterial Communities Over Tokyo and Influence of Local Meteorology

“…Airborne microorganisms were collected at a 458-m level measurement site (Misumi et al, 2018) on the western side of the Tokyo Skytree (Supplementary Table S1) from August 2016 to February 2017. Eight sets of 2-m-long conductive silicon tubes were fixed to the outside wall of the Tokyo Skytree with their inlets placed under a wind and rain shield, and sterilized inline NILU filter holders (Norwegian Institute for Air Research) attached to the inner ends.…”

Seasonal Trends of Atmospheric Ice Nucleating Particles Over Tokyo

“…Continuous year‐round measurements of clouds and aerosols over Tokyo have been conducted at a monitoring site located on the 458‐m level floor of Tokyo Skytree (35.71°N, 139.81°E) in Sumida, Tokyo, Japan (Misumi et al, 2018; Uetake et al, 2019). Ambient aerosol particles were carried to instruments installed in a monitoring room through a short length (~1.5 m) of 1/4″ conductive silicon tubes.…”

“…Recently, we started continuous in situ measurements of clouds and aerosols on Tokyo Skytree, which is the world's tallest television and radio broadcasting tower located in the Tokyo Metropolitan area in Japan (Misumi et al, 2018; Uetake et al, 2019). It is likely that low‐level stratiform clouds and aerosols measured over Tokyo are influenced by air masses originating from the Asian continental sources, as well as local/regional terrestrial and oceanic sources, especially from autumn to spring (Misumi et al, 2018; Uetake et al, 2019). It may also be important to note that the occurrence of summertime heavy rain events linked to complex urban land use‐weather‐climate feedbacks has been reported in large coastal cities like Tokyo (Misumi et al, 2019; Shepherd, 2005).…”

Clear-Air Echoes Observed by Ka-band Polarimetric Cloud Radar: A Case Study on Insect Echoes in the Tokyo Metropolitan Area, Japan

“…This study used the NIED polarimetric cloud radar (red dot in Fig. 1 the "CL" category, which indicates clouds that are not raining or drizzling, using the same approach as Misumi et al (2018). The bias was corrected so that extracted within the time classified into the "CL" category had a value of 0 dB.…”

“…Three of these radars have dual-polarization capability and the other two have single polarization. Millimeter-wavelength radars (Kollias et al 2007;Maesaka 2018), which are also referred to as cloud radars, are more sensitive to smaller particles than radars using centimeter wavelengths, which mainly measure precipitation particles. One of the targets of the NIED cloud radars is early detection of cumulonimbus clouds that cause short-term heavy rainfall.…”