Evaluation of Newly Developed Dropsonde for Aircraft Observation

A novel dropsonde, the iMDS-17, has been developed since 2017. The dropsonde was designed to be launched from an aircraft flying at an altitude of 13,000 m and ground speed of 720 km h−1. Owing to their light weight of approximately 130 g, parachutes are not necessary when observing upper-air atmospheric conditions throughout the troposphere. Approximately the same technology as that of the Japan Meteorological Agency (JMA) operational radiosonde (iMS-100) was used, except that the pressure was measured directly using a pressure sensor. To evaluate the performance of the iMDS-17, intercomparison experiments were conducted on 27 and 28 March 2024 on the southern island of Japan using a balloon-borne shooter system. The dropsonde and radiosonde were lifted by the same balloon and released at altitudes between 9,000 and 13,000 m. Comparison between data obtained from the experiments confirmed the adequate performance of iMDS-17 in temperature and wind observations; maximum differences between the dropsonde and radiosonde were less than 1 K and 2 m s−1 in temperature and wind, respectively, in most altitudes between 9-2 km. Meanwhile, a dry bias was identified for humidity, particularly in moist layers. The causes of the dry bias are discussed.