Dropwindsonde Instrumentation for Weather Reconnaissance Aircraft

Abstract

A windfinding dropsonde instrumentation system is described, with examples of its operational use in the GARP Atlantic Tropical Experiment conducted during the summer of 1974. Deployed from an aircraft flying typically at ?10 km altitude, the dropsonde transmits vertical profiles of horizontal wind, pressure, temperature and humidity while descending on a parachute at ?5 m s?1. The temperature sensor in the dropsonde is a 95-mil bead thermistor, the humidity sensor a standard carbon strip hygristor, and the pressure sensor an improved aneroid cell. Winds are determined by tracking the sonde using the 13.6 kHz Omega navigation signals received by an Omega receiver and retransmitted over a telemetry link. The telemetered data from a dropsonde are received, and recorded on-board the aircraft, using a computerized system configured to permit processing of two sondes descending simultaneously (one operating on 404.5 MHz, the other on 405.5 MHz).