In-situ observations in 30–40 km using radiosondes with large rubber balloons around western Pacific during YMC-BSM 2021

Abstract To observe small-scale wave activity, such as gravity waves, in the middle and upper stratosphere around the western Pacific, radiosonde observations with large rubber balloons were conducted on board the research vessel (R/V) Mirai from June to July 2021. This report describes the initial results of radiosonde observations, based on experimental observations, which have enabled us to obtain a large number of wind velocity and temperature data with high vertical resolution in the 30–40-km altitude range. The comparison results between reanalysis data and radiosonde observation data for wind velocity, and between Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC)-2 GNSS-RO data and radiosonde observation data for temperature are also reported to demonstrate that capturing the small vertical-scale waves that drive the middle atmospheric general circulation can be useful in revealing the structure of the middle atmospheric general circulation.