The Videosonde System and Its Use in the Study of East Asian Monsoon Rain

Abstract

Knowledge about precipitation particles in clouds is a prerequisite for the study of precipitation and cloud electrification mechanisms. A videosonde that can inform in-cloud precipitation particle shape and charge has been designed and more than 200 videosondes have been launched into monsoon clouds from 13 different locations in east Asia during the past 12 years. Rain is divided into three different regions with respect to the precipitation mechanisms: ?cool? in inland China, ?mixed? over the Maritime Continent, and ?frozen? over the west Pacific. Low concentrations of both ice crystal and graupel were observed over the west Pacific where lightning activities are weak. Ice crystals grew primarily on frozen drops and varied highly with different drop-size distributions near the melting level. Large cloud drops over the open ocean due to low CCN are slow to form ice crystals and suggest inactive ice crystal production. Electric charge measurements helped to study the particle evolution in rain systems. In squall lines, extensive recirculation of precipitation particles and rapid growth of frozen drops through capturing of supercooled drops from forward cells correlate with intense rainfall. Information about precipitation particles in heavy rain areas is essential for the study of precipitation and cloud electrification mechanisms. The purpose of this article is to demonstrate that a videosonde that can fly into any area of a rain system is a powerful tool to study rain and cloud electrification. The videosonde provides images of in-cloud precipitation particles ranging from cloud drop and ice crystal to raindrop, graupel, and hail as well as charges of precipitation particles. This article shows how important results were derived from each function of videosondes launched in East Asia monsoon clouds. More than 200 videosondes ascended from 13 different locations during the past 12 years. Highlights of this project are presented. It is hoped that this videosonde system will be used by workers in many different research fields related to the study of rain and electricity; enabling the sharing of knowledge obtained on East Asian monsoon rain.